Podcasts about smbhs

Join Hugh Ross in this breaking News of the Day episode of Stars, Cells, and God. Hugh describes the discovery of four fully-formed supermassive black holes that existed just 410–760 million years after the cosmic creation event. Do Early Supermassive Black Holes Refute the Big Bang? Quasar J1120+0641, seen 760 million years after the cosmic beginning, has a supermassive black hole (SMBH) weighing 1.52 billion solar masses. Quasar J1342+0928, seen 700 million years after the beginning, has a SMBH weighing 0.78 billion solar masses. Quasar J0313-1806, seen 690 million years after the beginning, has a SMBH of 1.6 billion solar masses. The most distantly detected SMBH belongs to GN-z11. Just 410 million after the beginning, its SMBH weighs 0.002 billion solar masses. There are three ways such SMBHs can form so early in a big bang universe: through 1) very aggressive early gas accretion by the BHs; 2) mergers of the BHs arising from many 500+ solar-mass first generation stars; and 3) mergers of 10,000+ solar-mass gas clouds that collapse into black holes without forming stars. The discovery of many more cosmic dawn SMBHs will determine which one, of more, of the three ways explains the SMBHs.  Links & Resources A Mature Quasar at Cosmic Dawn Revealed by JWST Rest-Frame Infrared Spectroscopy Black Holes as Evidence of God's Care

La tertulia semanal en la que repasamos las últimas noticias de la actualidad científica. En el episodio de hoy:Cara B:-ATLAS y CMS estudian la desintegración del bosón de Higgs en un bosón Z y un fotón (00:05)-Cociente de masas de agujero negro central a masa total para galaxias a z>4 (24:02)-Evolución dinámica de la masa relativa de agujeros negros supermasivos y la masa de la galaxia anfitriona a redshift z=2 (43:22)-La evaporación de agujeros negros primordiales podría mantener las nubes de H calientes y permitir las semillas tempranas de SMBHs (48:22)-Entrelazamiento cuántico entre quarks en chorros hadrónicos (58:22)-Señales de los oyentes (1:22:22)Este episodio es continuación de la Cara A.Contertulios: Gastón Giribet, Francis Villatoro, Héctor Socas. Imagen de portada realizada con Midjourney. Todos los comentarios vertidos durante la tertulia representan únicamente la opinión de quien los hace... y a veces ni eso Hosted on Acast. See acast.com/privacy for more information.

Modeling Reconstructed Images of Jets Launched by SANE Super-Eddington Accretion Flows Around SMBHs with the ngEHT by Brandon Curd et al. on Wednesday 30 November Tidal disruption events (TDEs) around super massive black holes (SMBHs) are a potential laboratory to study super-Eddington accretion disks and sometimes result in powerful jets or outflows which may shine in the radio and sub millimeter bands. In this work, we model the thermal synchrotron emission of jets from general relativistic radiation magneto-hydrodynamics (GRRMHD) simulations of a BH accretion disk/jet system which assumes the TDE resulted in a magnetized accretion disk around a BH accreting at $sim 12-25$ times the Eddington accretion rate. Through synthetic observations with the Next Generation Event Horizon Telescope (ngEHT) and an image reconstruction analysis, we demonstrate that TDE jets may provide compelling targets, within the context of the models explored in this work. In particular, we find that jets launched by a SANE super-Eddington disk around a spin $a_*=0.9$ reach the ngEHT detection threshold at large distances (up to 100 Mpc in this work). A two-temperature plasma in the jet or weaker jets, such as a spin $a_*=0$ model, requires a much closer distance as we demonstrate detection at 10 Mpc for limiting cases of $a_*=0,,mathcal{R}=1$ or $a_*=0.9,, mathcal{R}=20$. We also demonstrate that TDE jets may appear as superluminal sources if the BH is rapidly rotating and the jet is viewed nearly face on. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.15906v1

BASS XXXIX: Swift-BAT AGN with changing-look optical spectra by Matthew J. Temple et al. on Wednesday 30 November Changing-look (CL) AGN are unique probes of accretion onto supermassive black holes (SMBHs), especially when simultaneous observations in complementary wavebands allow investigations into the properties of their accretion flows. We present the results of a search for CL behaviour in 412 Swift-BAT detected AGN with multiple epochs of optical spectroscopy from the BAT AGN Spectroscopic Survey (BASS). 125 of these AGN also have 14-195 keV ultra-hard X-ray light-curves from Swift-BAT which are contemporaneous with the epochs of optical spectroscopy. Eight CL events are presented for the first time, where the appearance or disappearance of broad Balmer line emission leads to a change in the observed Seyfert type classification. Combining with known events from the literature, 21 AGN from BASS are now known to display CL behaviour. Nine CL events have 14-195 keV data available, and five of these CL events can be associated with significant changes in their 14-195 keV flux from BAT. The ultra-hard X-ray flux is less affected by obscuration and so these changes in the 14-195 keV band suggest that the majority of our CL events are not due to changes in line-of-sight obscuration. We derive a CL rate of 0.7-6.2 per cent on 10-25 year time-scales, and show that many transitions happen within at most a few years. Our results motivate further multi-wavelength observations with higher cadence to better understand the variability physics of accretion onto SMBHs. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.04478v2

A very luminous jet from the disruption of a star by a massive black hole by Igor Andreoni et al. on Wednesday 30 November Tidal disruption events (TDEs) are bursts of electromagnetic energy released when supermassive black holes (SMBHs) at the centers of galaxies violently disrupt a star that passes too close. TDEs provide a new window to study accretion onto SMBHs; in some rare cases, this accretion leads to launching of a relativistic jet, but the necessary conditions are not fully understood. The best studied jetted TDE to date is Swift J1644+57, which was discovered in gamma-rays, but was too obscured by dust to be seen at optical wavelengths. Here we report the optical discovery of AT2022cmc, a rapidly fading source at cosmological distance (redshift z=1.19325) whose unique lightcurve transitioned into a luminous plateau within days. Observations of a bright counterpart at other wavelengths, including X-rays, sub-millimeter, and radio, supports the interpretation of AT2022cmc as a jetted TDE containing a synchrotron "afterglow", likely launched by a SMBH with spin $a gtrsim 0.3$. Using 4 years of Zwicky Transient Facility (ZTF) survey data, we calculate a rate of $0.02 ^{+ 0.04 }_{- 0.01 }$ Gpc$^{-3}$ yr$^{-1}$ for on-axis jetted TDEs based on the luminous, fast-fading red component, thus providing a measurement complementary to the rates derived from X-ray and radio observations. Correcting for the beaming angle effects, this rate confirms that about 1% of TDEs have relativistic jets. Optical surveys can use AT2022cmc as a prototype to unveil a population of jetted TDEs. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.16530v1

BASS XXXIX: Swift-BAT AGN with changing-look optical spectra by Matthew J. Temple et al. on Wednesday 30 November Changing-look (CL) AGN are unique probes of accretion onto supermassive black holes (SMBHs), especially when simultaneous observations in complementary wavebands allow investigations into the properties of their accretion flows. We present the results of a search for CL behaviour in 412 Swift-BAT detected AGN with multiple epochs of optical spectroscopy from the BAT AGN Spectroscopic Survey (BASS). 125 of these AGN also have 14-195 keV ultra-hard X-ray light-curves from Swift-BAT which are contemporaneous with the epochs of optical spectroscopy. Eight CL events are presented for the first time, where the appearance or disappearance of broad Balmer line emission leads to a change in the observed Seyfert type classification. Combining with known events from the literature, 21 AGN from BASS are now known to display CL behaviour. Nine CL events have 14-195 keV data available, and five of these CL events can be associated with significant changes in their 14-195 keV flux from BAT. The ultra-hard X-ray flux is less affected by obscuration and so these changes in the 14-195 keV band suggest that the majority of our CL events are not due to changes in line-of-sight obscuration. We derive a CL rate of 0.7-6.2 per cent on 10-25 year time-scales, and show that many transitions happen within at most a few years. Our results motivate further multi-wavelength observations with higher cadence to better understand the variability physics of accretion onto SMBHs. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.04478v2

BASS XXXIX: Swift-BAT AGN with changing-look optical spectra by Matthew J. Temple et al. on Wednesday 30 November Changing-look (CL) AGN are unique probes of accretion onto supermassive black holes (SMBHs), especially when simultaneous observations in complementary wavebands allow investigations into the properties of their accretion flows. We present the results of a search for CL behaviour in 412 Swift-BAT detected AGN with multiple epochs of optical spectroscopy from the BAT AGN Spectroscopic Survey (BASS). 125 of these AGN also have 14-195 keV ultra-hard X-ray light-curves from Swift-BAT which are contemporaneous with the epochs of optical spectroscopy. Eight CL events are presented for the first time, where the appearance or disappearance of broad Balmer line emission leads to a change in the observed Seyfert type classification. Combining with known events from the literature, 21 AGN from BASS are now known to display CL behaviour. Nine CL events have 14-195 keV data available, and five of these CL events can be associated with significant changes in their 14-195 keV flux from BAT. The ultra-hard X-ray flux is less affected by obscuration and so these changes in the 14-195 keV band suggest that the majority of our CL events are not due to changes in line-of-sight obscuration. We derive a CL rate of 0.7-6.2 per cent on 10-25 year time-scales, and show that many transitions happen within at most a few years. Our results motivate further multi-wavelength observations with higher cadence to better understand the variability physics of accretion onto SMBHs. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.04478v2

The Circumgalactic Medium of Milky Way-like Galaxies in the TNG50 Simulation -- I: Halo Gas Properties and the Role of SMBH Feedback by Rahul Ramesh et al. on Wednesday 30 November We analyze the physical properties of gas in the circumgalactic medium (CGM) of 132 Milky Way (MW)-like galaxies at $z=0$ from the cosmological magneto-hydrodynamical simulation TNG50, part of the IllustrisTNG project. The properties and abundance of CGM gas across the sample are diverse, and the fractional budgets of different phases (cold, warm, and hot), as well as neutral HI mass and metal mass, vary considerably. Over our stellar mass range of $10^{10.5} < M_star / rm{M}_odot < 10^{10.9}$, radial profiles of gas physical properties from $0.15 < Rrm{ / R_{rm 200c}} < 1.0$ reveal great CGM structural complexity, with significant variations both at fixed distance around individual galaxies, and across different galaxies. CGM gas is multi-phase: the distributions of density, temperature and entropy are all multimodal, while metallicity and thermal pressure distributions are unimodal; all are broad. We present predictions for magnetic fields in MW-like halos: a median field strength of $|B|sim,1mu$G in the inner halo decreases rapidly at larger distance, while magnetic pressure dominates over thermal pressure only within $sim0.2 times rm{R_{200c}}$. Virial temperature gas at $sim 10^6,$K coexists with a sub-dominant cool, $< 10^5,$K component in approximate pressure equilibrium. Finally, the physical properties of the CGM are tightly connected to the galactic star formation rate, in turn dependent on feedback from supermassive black holes (SMBHs). In TNG50, we find that energy from SMBH-driven kinetic winds generates high-velocity outflows ($gtrsim 500-2000$ km/s), heats gas to super-virial temperatures ($> 10^{6.5-7}$ K), and regulates the net balance of inflows versus outflows in otherwise quasi-static gaseous halos. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.00020v2

The Circumgalactic Medium of Milky Way-like Galaxies in the TNG50 Simulation -- I: Halo Gas Properties and the Role of SMBH Feedback by Rahul Ramesh et al. on Tuesday 29 November We analyze the physical properties of gas in the circumgalactic medium (CGM) of 132 Milky Way (MW)-like galaxies at $z=0$ from the cosmological magneto-hydrodynamical simulation TNG50, part of the IllustrisTNG project. The properties and abundance of CGM gas across the sample are diverse, and the fractional budgets of different phases (cold, warm, and hot), as well as neutral HI mass and metal mass, vary considerably. Over our stellar mass range of $10^{10.5} < M_star / rm{M}_odot < 10^{10.9}$, radial profiles of gas physical properties from $0.15 < Rrm{ / R_{rm 200c}} < 1.0$ reveal great CGM structural complexity, with significant variations both at fixed distance around individual galaxies, and across different galaxies. CGM gas is multi-phase: the distributions of density, temperature and entropy are all multimodal, while metallicity and thermal pressure distributions are unimodal; all are broad. We present predictions for magnetic fields in MW-like halos: a median field strength of $|B|sim,1mu$G in the inner halo decreases rapidly at larger distance, while magnetic pressure dominates over thermal pressure only within $sim0.2 times rm{R_{200c}}$. Virial temperature gas at $sim 10^6,$K coexists with a sub-dominant cool, $< 10^5,$K component in approximate pressure equilibrium. Finally, the physical properties of the CGM are tightly connected to the galactic star formation rate, in turn dependent on feedback from supermassive black holes (SMBHs). In TNG50, we find that energy from SMBH-driven kinetic winds generates high-velocity outflows ($gtrsim 500-2000$ km/s), heats gas to super-virial temperatures ($> 10^{6.5-7}$ K), and regulates the net balance of inflows versus outflows in otherwise quasi-static gaseous halos. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.00020v2

Modeling Reconstructed Images of Jets Launched by SANE Super-Eddington Accretion Flows Around SMBHs with the ngEHT by Brandon Curd et al. on Tuesday 29 November Tidal disruption events (TDEs) around super massive black holes (SMBHs) are a potential laboratory to study super-Eddington accretion disks and sometimes result in powerful jets or outflows which may shine in the radio and sub millimeter bands. In this work, we model the thermal synchrotron emission of jets from general relativistic radiation magneto-hydrodynamics (GRRMHD) simulations of a BH accretion disk/jet system which assumes the TDE resulted in a magnetized accretion disk around a BH accreting at $sim 12-25$ times the Eddington accretion rate. Through synthetic observations with the Next Generation Event Horizon Telescope (ngEHT) and an image reconstruction analysis, we demonstrate that TDE jets may provide compelling targets, within the context of the models explored in this work. In particular, we find that jets launched by a SANE super-Eddington disk around a spin $a_*=0.9$ reach the ngEHT detection threshold at large distances (up to 100 Mpc in this work). A two-temperature plasma in the jet or weaker jets, such as a spin $a_*=0$ model, requires a much closer distance as we demonstrate detection at 10 Mpc for limiting cases of $a_*=0,,mathcal{R}=1$ or $a_*=0.9,, mathcal{R}=20$. We also demonstrate that TDE jets may appear as superluminal sources if the BH is rapidly rotating and the jet is viewed nearly face on. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.15906v1

First detections of stellar light from quasar host galaxies at z > 6 by Xuheng Ding et al. on Tuesday 29 November The existence of high-redshift supermassive black holes (SMBHs) -- shining brightly as quasars during the first billion years of our universe -- presents a conundrum in astrophysics. A broad variety of physical mechanisms have been proposed for the formation and rapid growth of these early SMBHs. Promising diagnostics are the relative properties of the black hole and its host galaxy. However, up to now, the detection of stars in quasar host galaxies has been elusive beyond $z>2$, even with deep HST observations. Here, we report the first detections of the stellar component of the host galaxies of two relatively low-luminosity quasars at $z>6$ observed with JWST using NIRCam. After modeling and subtracting the glare from the quasar itself, we find that the host galaxies are massive (stellar mass of $2.5times$ and $6.3times10^{10}$ M$_{odot}$), compact, and disk-like. Unlike most SMBHs in the nearby universe, these quasars are displaced from the centers of their host galaxies in the rest-frame optical, in one case by $0.9$ kpc. These first positive detections of quasar hosts at $z>6$ are a pivotal milestone; we can now assess the stellar environment along with star formation and black hole accretion to determine the physical conditions that govern the formation and evolution of the first SMBHs. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.14329v1

Evidence for non-merger co-evolution of galaxies and their supermassive black holes by R. J. Smethurst et al. on Monday 28 November Recent observational and theoretical studies have suggested that supermassive black holes (SMBHs) grow mostly through non-merger (`secular') processes. Since galaxy mergers lead to dynamical bulge growth, the only way to observationally isolate non-merger growth is to study galaxies with low bulge-to-total mass ratio (e.g. B/T < 10%). However, bulge growth can also occur due to secular processes, such as disk instabilities, making disk-dominated selections a somewhat incomplete way to select merger-free systems. Here we use the Horizon-AGN simulation to select simulated galaxies which have not undergone a merger since z = 2, regardless of bulge mass, and investigate their location on typical black hole-galaxy scaling relations in comparison to galaxies with merger dominated histories. While the existence of these correlations has long been interpreted as co-evolution of galaxies and their SMBHs driven by galaxy mergers, we show here that they persist even in the absence of mergers. We find that the correlations between SMBH mass and both total mass and stellar velocity dispersion are independent of B/T ratio for both merger-free and merger-dominated galaxies. In addition, the bulge mass and SMBH mass correlation is still apparent for merger-free galaxies, the intercept for which is dependent on B/T. Galaxy mergers reduce the scatter around the scaling relations, with merger-free systems showing broader scatter. We show that for merger-free galaxies, the co-evolution is dominated by radio-mode feedback, and suggest that the long periods of time between galaxy mergers make an important contribution to the co-evolution between galaxies and SMBHs in all galaxies. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.13677v1

Supermassive black holes in merger-free galaxies have higher spins which are preferentially aligned with their host galaxy by R. S. Beckmann et al. on Monday 28 November Here we use the Horizon-AGN simulation to test whether the spins of SMBHs in merger-free galaxies are higher. We select samples using an observationally motivated bulge-to-total mass ratio of < 0.1, along with two simulation motivated thresholds selecting galaxies which have not undergone a galaxy merger since z = 2, and those SMBHs with < 10% of their mass due to SMBH mergers. We find higher spins (> 5{sigma} ) in all three samples compared to the rest of the population. In addition, we find that SMBHs with their growth dominated by BH mergers following galaxy mergers, are less likely to be aligned with their galaxy spin than those that have grown through accretion in the absence of galaxy mergers (3.4{sigma} ). We discuss the implications this has for the impact of active galactic nuclei (AGN) feedback, finding that merger-free SMBHs spend on average 91% of their lifetimes since z = 2 in a radio mode of feedback (88% for merger-dominated galaxies). Given that previous observational and theoretical works have concluded that merger-free processes dominate SMBH-galaxy co-evolution, our results suggest that this co-evolution could be regulated by radio mode AGN feedback. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.13614v1

First detections of stellar light from quasar host galaxies at z > 6 by Xuheng Ding et al. on Monday 28 November The existence of high-redshift supermassive black holes (SMBHs) -- shining brightly as quasars during the first billion years of our universe -- presents a conundrum in astrophysics. A broad variety of physical mechanisms have been proposed for the formation and rapid growth of these early SMBHs. Promising diagnostics are the relative properties of the black hole and its host galaxy. However, up to now, the detection of stars in quasar host galaxies has been elusive beyond $z>2$, even with deep HST observations. Here, we report the first detections of the stellar component of the host galaxies of two relatively low-luminosity quasars at $z>6$ observed with JWST using NIRCam. After modeling and subtracting the glare from the quasar itself, we find that the host galaxies are massive (stellar mass of $2.5times$ and $6.3times10^{10}$ M$_{odot}$), compact, and disk-like. Unlike most SMBHs in the nearby universe, these quasars are displaced from the centers of their host galaxies in the rest-frame optical, in one case by $0.9$ kpc. These first positive detections of quasar hosts at $z>6$ are a pivotal milestone; we can now assess the stellar environment along with star formation and black hole accretion to determine the physical conditions that govern the formation and evolution of the first SMBHs. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.14329v1

Evidence for non-merger co-evolution of galaxies and their supermassive black holes by R. J. Smethurst et al. on Sunday 27 November Recent observational and theoretical studies have suggested that supermassive black holes (SMBHs) grow mostly through non-merger (`secular') processes. Since galaxy mergers lead to dynamical bulge growth, the only way to observationally isolate non-merger growth is to study galaxies with low bulge-to-total mass ratio (e.g. B/T < 10%). However, bulge growth can also occur due to secular processes, such as disk instabilities, making disk-dominated selections a somewhat incomplete way to select merger-free systems. Here we use the Horizon-AGN simulation to select simulated galaxies which have not undergone a merger since z = 2, regardless of bulge mass, and investigate their location on typical black hole-galaxy scaling relations in comparison to galaxies with merger dominated histories. While the existence of these correlations has long been interpreted as co-evolution of galaxies and their SMBHs driven by galaxy mergers, we show here that they persist even in the absence of mergers. We find that the correlations between SMBH mass and both total mass and stellar velocity dispersion are independent of B/T ratio for both merger-free and merger-dominated galaxies. In addition, the bulge mass and SMBH mass correlation is still apparent for merger-free galaxies, the intercept for which is dependent on B/T. Galaxy mergers reduce the scatter around the scaling relations, with merger-free systems showing broader scatter. We show that for merger-free galaxies, the co-evolution is dominated by radio-mode feedback, and suggest that the long periods of time between galaxy mergers make an important contribution to the co-evolution between galaxies and SMBHs in all galaxies. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.13677v1

Supermassive black holes in merger-free galaxies have higher spins which are preferentially aligned with their host galaxy by R. S. Beckmann et al. on Sunday 27 November Here we use the Horizon-AGN simulation to test whether the spins of SMBHs in merger-free galaxies are higher. We select samples using an observationally motivated bulge-to-total mass ratio of < 0.1, along with two simulation motivated thresholds selecting galaxies which have not undergone a galaxy merger since z = 2, and those SMBHs with < 10% of their mass due to SMBH mergers. We find higher spins (> 5{sigma} ) in all three samples compared to the rest of the population. In addition, we find that SMBHs with their growth dominated by BH mergers following galaxy mergers, are less likely to be aligned with their galaxy spin than those that have grown through accretion in the absence of galaxy mergers (3.4{sigma} ). We discuss the implications this has for the impact of active galactic nuclei (AGN) feedback, finding that merger-free SMBHs spend on average 91% of their lifetimes since z = 2 in a radio mode of feedback (88% for merger-dominated galaxies). Given that previous observational and theoretical works have concluded that merger-free processes dominate SMBH-galaxy co-evolution, our results suggest that this co-evolution could be regulated by radio mode AGN feedback. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.13614v1

Nuclear Activity in the Low Metallicity Dwarf Galaxy SDSS J0944-0038: A Glimpse into the Primordial Universe by Michael Reefe et al. on Friday 25 November Local low metallicity dwarf galaxies are relics of the early universe and hold clues into the origins of supermassive black holes (SMBHs). In recent work, coronal lines have been used to unveil a population of candidate accreting black holes in dwarf galaxies with gas phase metallicities and stellar masses well below the host galaxies of any previously known AGNs. Using MUSE/VLT observations, we report the detection of [Fe X] $lambda$6374 coronal line emission and a broad H$alpha$ line in the nucleus of SDSS J094401.87$-$003832.1, a nearby ($z=0.0049$) metal poor dwarf galaxy at least fifty times less massive than the LMC. The [Fe X] $lambda$6374 emission is compact and centered on the brightest nuclear source, with a spatial extent of $approx$100 pc. The [Fe X] luminosity is $approx 10^{37}$ erg s$^{-1}$, within the range seen in previously identified AGNs in the dwarf galaxy population. This line has never been observed in gas ionized by hot stars. While it can be produced in supernova ejecta, the [Fe X] flux from SDSS J094401.87$-$003832.1 has persisted over the ~19 year time period between the SDSS and MUSE observations, ruling out supernovae as the origin for the emission. The FWHM of the broad component of the H$alpha$ line is $446 pm 17$ km s$^{-1}$ and its luminosity is $approx 1.5times10^{38}$ erg s$^{-1}$, lower than the broad line luminosities of previously identified low mass broad line AGNs. These observations, together with previously reported multi-wavelength observations, can most plausibly be explained by the presence of an accreting intermediate mass black hole in a primordial galaxy analog. However, we cannot rule out the possibility that current stellar population models of metal poor stars significantly under-predict the stellar ionizing photon flux, and that metal poor stars can produce an extreme ionizing spectrum similar to that produced by AGNs. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.13179v1

Nuclear Activity in the Low Metallicity Dwarf Galaxy SDSS J0944-0038: A Glimpse into the Primordial Universe by Michael Reefe et al. on Thursday 24 November Local low metallicity dwarf galaxies are relics of the early universe and hold clues into the origins of supermassive black holes (SMBHs). In recent work, coronal lines have been used to unveil a population of candidate accreting black holes in dwarf galaxies with gas phase metallicities and stellar masses well below the host galaxies of any previously known AGNs. Using MUSE/VLT observations, we report the detection of [Fe X] $lambda$6374 coronal line emission and a broad H$alpha$ line in the nucleus of SDSS J094401.87$-$003832.1, a nearby ($z=0.0049$) metal poor dwarf galaxy at least fifty times less massive than the LMC. The [Fe X] $lambda$6374 emission is compact and centered on the brightest nuclear source, with a spatial extent of $approx$100 pc. The [Fe X] luminosity is $approx 10^{37}$ erg s$^{-1}$, within the range seen in previously identified AGNs in the dwarf galaxy population. This line has never been observed in gas ionized by hot stars. While it can be produced in supernova ejecta, the [Fe X] flux from SDSS J094401.87$-$003832.1 has persisted over the ~19 year time period between the SDSS and MUSE observations, ruling out supernovae as the origin for the emission. The FWHM of the broad component of the H$alpha$ line is $446 pm 17$ km s$^{-1}$ and its luminosity is $approx 1.5times10^{38}$ erg s$^{-1}$, lower than the broad line luminosities of previously identified low mass broad line AGNs. These observations, together with previously reported multi-wavelength observations, can most plausibly be explained by the presence of an accreting intermediate mass black hole in a primordial galaxy analog. However, we cannot rule out the possibility that current stellar population models of metal poor stars significantly under-predict the stellar ionizing photon flux, and that metal poor stars can produce an extreme ionizing spectrum similar to that produced by AGNs. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.13179v1

X-ray from Outflow-Cloud Interaction and Its Application in Tidal Disruption Events by Jiashi Chen et al. on Monday 21 November Tidal disruption events (TDEs) may occur in supermassive black holes (SMBHs) surrounded by clouds. TDEs can generate ultrafast and large opening-angle outflow with a velocity of $sim$ 0.01--0.2 c, which will collide with clouds with time lags depending on outflow velocity and cloud distances. Since the fraction of the outflow energy transferred into cloud's radiation is anti-correlated with the cloud density, high density clouds was thought to be inefficient in generating radiation. In this work, we studied the radiation from the outflow-cloud interactions for high density clouds, and found that thermal conduction plays crucial roles in increasing the cloud's radiation. Up to 10% of the bow shock energy can be transferred into clouds and gives rise to X-ray emission with equivalent temperature of $10^{5-6}$ Kelvins due to the cooling catastrophe. The inverse Compton scattering of TDE UV/optical photons by relativistic electrons at bow shock generates power-law X-ray spectra with photon indices $Gammasim 2-3$. This mechanism may account for some TDE candidates with delayed X-ray emission, and can be examined by delayed radio and gamma-ray emissions. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.10004v1

BASS XXXVI Constraining the Local Supermassive Black Hole - Halo Connection with BASS DR2 AGN by M. C. Powell et al. on Monday 17 October We investigate the connection between supermassive black holes (SMBHs) and their host dark matter halos in the local universe using the clustering statistics and luminosity function of AGN from the Swift/BAT AGN Spectroscopic survey (BASS DR2). By forward-modeling AGN activity into snapshot halo catalogs from N-body simulations, we test a scenario in which SMBH mass correlates with dark matter (sub)halo mass for fixed stellar mass. We compare this to a model absent of this correlation, where stellar mass alone determines the SMBH mass. We find that while both simple models are able to largely reproduce the abundance and overall clustering of AGN, the model in which black hole mass is tightly correlated with halo mass is preferred by the data by $1.8sigma$. When including an independent measurement on the black hole mass-halo mass correlation, this model is preferred by $4.6sigma$. We show that the clustering trends with black hole mass can further break the degeneracies between the two scenarios, and that our preferred model reproduces the measured clustering differences on 1-halo scales between large and small black hole masses. These results indicate that the halo binding energy is fundamentally connected to the growth of supermassive black holes. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.02728v2

Collimation of the relativistic jet in the quasar 3C 273 by Hiroki Okino et al. on Monday 10 October The collimation of relativistic jets launched from the vicinity of supermassive black holes (SMBHs) at the centers of active galactic nuclei (AGN) is one of the key questions to understand the nature of AGN jets. However, little is known about the detailed jet structure for AGN like quasars since very high angular resolutions are required to resolve these objects. We present very long baseline interferometry (VLBI) observations of the archetypical quasar 3C 273 at 86 GHz, performed with the Global Millimeter VLBI Array, for the first time including the Atacama Large Millimeter/submillimeter Array. Our observations achieve a high angular resolution down to $sim$60 ${rm mu}$as, resolving the innermost part of the jet ever on scales of $sim 10^5$ Schwarzschild radii. Our observations, including close-in-time High Sensitivity Array observations of 3C 273 at 15, 22, and 43 GHz, suggest that the inner jet collimates parabolically, while the outer jet expands conically, similar to jets from other nearby low luminosity AGN. We discovered the jet collimation break around $10^{7}$ Schwarzschild radii, providing the first compelling evidence for structural transition in a quasar jet. The location of the collimation break for 3C 273 is farther downstream the sphere of gravitational influence (SGI) from the central SMBH. With the results for other AGN jets, our results show that the end of the collimation zone in AGN jets is governed not only by the SGI of the SMBH but also by the more diverse properties of the central nuclei. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2112.12233v2

A Close Quasar Pair in a Disk-Disk Galaxy Merger at z = 2 17 by Yu-Ching Chen et al. on Sunday 25 September Most local massive galaxies, if not all, are believed to harbor a supermassive black hole (SMBH) at the center. Galaxy mergers have long been thought to drive strong gas inflows and accretion onto one or both central SMBH, triggering single or dual quasars as a natural stage of the hierarchical galaxy and SMBH evolution. While many dual active galactic nuclei -- the low-luminosity counterparts of quasars -- have been observed at low redshift, no unambiguous dual quasar is known at cosmic noon (z>~2) when both quasar activity and global star formation density peaked. While a handful of dual quasar candidates were known at z>1, competing explanations remained. Here we report multi-wavelength observations of SDSS J0749+2255 as the first kpc-scale dual quasar confirmed to be hosted by a galaxy merger at cosmic noon. Hubble Space Telescope NIR imaging reveals extended host galaxies underlying the compact double nuclei (separated by 0.46" or 3.8 kpc) and tidal features as evidence for galactic interactions. We also present new multi-wavelength observations, all lending support to the dual quasar hypothesis. Unlike the low-redshift low-luminosity counterparts, the high-redshift dual quasar is hosted by two massive compact disk-dominated galaxies, which may be critical for efficient gas fueling onto the SMBHs in the early-stage merger. The apparent lack of stellar bulges and that SDSS J0749+2255 already follows the local SMBH mass-host stellar mass relation are at odds with the canonical SMBH-host co-evolution picture and suggest that at least some SMBHs may have formed before their host stellar bulges. While still at kpc-scale separations where the host-galaxy gravitational potential dominates, the SMBHs may evolve into a gravitationally bound binary system in ~0.22 Gyr. The merger products at low redshift are expected to be gravitational wave sources for pulsar-timing arrays (abridged). arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.11249v1

Supermassive Black Hole and Broad-line Region in NGC~5548: Results from Five-season Reverberation Mapping by Kai-Xing Lu et al. on Sunday 25 September NGC 5548 is one of the active galactic nuclei (AGN) selected for our long-term spectroscopic monitoring with the Lijiang 2.4~m telescope, aiming at investigating the origin and evolution of the broad-line regions (BLRs), accurately measuring the mass of the supermassive black holes (SMBHs), and understanding structure and evolution of the AGN. We have performed five-season observations for NGC~5548 with the median sampling interval ranging from 1.25 to 3 days. The light curves of the 5100~AA continuum and broad emission lines are measured after subtracting contamination of the host galaxy starlight. The time lags of the broad He~{sc ii}, He~{sc i}, H$gamma$, and H$beta$ lines with respect to the 5100~AA continuum are obtained for each season and their mean time lags over the five seasons are 0.69, 4.66, 4.60, 8.43 days, respectively. The H$gamma$ and H$beta$ velocity-resolved lag profiles in the seasons of 2015, 2018, 2019, and 2021 are constructed, from which an ``M-shaped'' structure is found in 2015 but disappears after 2018. Our five-season reverberation mapping (RM) yields an averaged virial SMBH mass of $M_bullet/10^7M_odot=14.22$, with a small standard deviation of $1.89$. By combining the previous 18 RM campaigns and our five-season campaign for NGC~5548, we find that there exists a time lag of 3.5~years between the changes in the BLR size and optical luminosity. In addition, we also construct the BLR radius$-$luminosity relation and the virial relation for NGC~5548. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.10853v2

Coevolution of Supermassive Black Holes and their Host Galaxies with Galaxy Mergers by Chi-Hong Lin et al. on Thursday 22 September Understanding the formation of the supermassive black holes (SMBHs) present in the centers of galaxies is a key topic in modern astrophysics. Observations have detected the SMBHs with mass $M$ of $10^{9}, rm M_odot$ in the high redshifts galaxies with z$sim7$. However, how SMBHs grew to such huge masses within the first billion years after the big bang remains elusive. One possible explanation is that SMBHs grew in a short period through the frequent mergers of galaxies, which provides sustainable gas to maintain the rapid growth. In this study, we present the hydrodynamics simulations of the SMBHs' growth with their host galaxies using the GIZMO code. In contrast to previous simulations, we developed a molecular cloud model by separating molecular-gas particles from the atomic-gas particles and then evolving them independently. During major mergers, we showed that the effect of the mass segregation of the atomic and molecular gas particles can enhance the dynamical friction of molecular particles. Consequently, molecular gas is substantially accreted onto the galactic centers that grows SMBHs from $10^{6}, rm M_odot$ to $10^{9}, rm M_odot$ within 300 Myr, explaining the rapid growth of SMBHs, and this accretion also triggers a violent starburst at the galactic center. Furthermore, We examined the impact of minor mergers on the bulge of a Milky-Way-like galaxy and found that the size and mass of the bulge can increase from 0.92 kpc to 1.9 kpc and from $4.7times 10^{10}, rm M_odot$ to $7times 10^{10}, rm M_odot$. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.10535v1

Supermassive Black Hole and Broad-line Region in NGC~5548: Results from Five-season Reverberation Mapping by Ka-Xing Lu et al. on Thursday 22 September NGC 5548 is one of the active galactic nuclei (AGN) selected for our long-term spectroscopic monitoring with the Lijiang 2.4~m telescope, aiming at investigating the origin and evolution of the broad-line regions (BLRs), accurately measuring the mass of the supermassive black holes (SMBHs), and understanding structure and evolution of the AGN. We have performed five-season observations for NGC~5548 with the median sampling interval ranging from 1.25 to 3 days. The light curves of the 5100~AA continuum and broad emission lines are measured after subtracting contamination of the host galaxy starlight. The time lags of the broad He~{sc ii}, He~{sc i}, H$gamma$, and H$beta$ lines with respect to the 5100~AA continuum are obtained for each season and their mean time lags over the five seasons are 0.69, 4.66, 4.60, 8.43 days, respectively. The H$gamma$ and H$beta$ velocity-resolved lag profiles in the seasons of 2015, 2018, 2019, and 2021 are constructed, from which an ``M-shaped'' structure is found in 2015 but disappears after 2018. Our five-season reverberation mapping (RM) yields an averaged virial SMBH mass of $M_bullet/10^7M_odot=14.22$, with a small standard deviation of $1.89$. By combining the previous 18 RM campaigns and our five-season campaign for NGC~5548, we find that there exists a time lag of 3.5~years between the changes in the BLR size and optical luminosity. In addition, we also construct the BLR radius$-$luminosity relation and the virial relation for NGC~5548. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.10853v1

Coevolution of Supermassive Black Holes and their Host Galaxies with Galaxy Mergers by Chi-Hong Lin et al. on Thursday 22 September Understanding the formation of the supermassive black holes (SMBHs) present in the centers of galaxies is a key topic in modern astrophysics. Observations have detected the SMBHs with mass $M$ of $10^{9}, rm M_odot$ in the high redshifts galaxies with z$sim7$. However, how SMBHs grew to such huge masses within the first billion years after the big bang remains elusive. One possible explanation is that SMBHs grew in a short period through the frequent mergers of galaxies, which provides sustainable gas to maintain the rapid growth. In this study, we present the hydrodynamics simulations of the SMBHs' growth with their host galaxies using the GIZMO code. In contrast to previous simulations, we developed a molecular cloud model by separating molecular-gas particles from the atomic-gas particles and then evolving them independently. During major mergers, we showed that the effect of the mass segregation of the atomic and molecular gas particles can enhance the dynamical friction of molecular particles. Consequently, molecular gas is substantially accreted onto the galactic centers that grows SMBHs from $10^{6}, rm M_odot$ to $10^{9}, rm M_odot$ within 300 Myr, explaining the rapid growth of SMBHs, and this accretion also triggers a violent starburst at the galactic center. Furthermore, We examined the impact of minor mergers on the bulge of a Milky-Way-like galaxy and found that the size and mass of the bulge can increase from 0.92 kpc to 1.9 kpc and from $4.7times 10^{10}, rm M_odot$ to $7times 10^{10}, rm M_odot$. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.10535v1

The rebrightening of AT2018fyk as a repeating partial tidal disruption event by T. Wevers et al. on Monday 19 September Stars that interact with supermassive black holes (SMBHs) can either be completely or partially destroyed by tides. In a partial tidal disruption event (TDE) the high-density core of the star remains intact, and the low-density, outer envelope of the star is stripped and feeds a luminous accretion episode. The TDE AT2018fyk, with an inferred black hole mass of $10^{7.7pm0.4}$ M$_{odot}$, experienced an extreme dimming event at X-ray (factor of $>$6000) and UV (factor $sim$15) wavelengths $sim$500--600 days after discovery. Here we report on the re-emergence of these emission components roughly 1200 days after discovery. We find that the source properties are similar to those of the pre-dimming accretion state, suggesting that the accretion flow was rejuvenated to a similar state. We propose that a repeating partial TDE, where the partially disrupted star is on a $sim 1200$ day orbit about the SMBH and is periodically stripped of mass during each pericenter passage, powers its unique lightcurve. This scenario provides a plausible explanation for AT2018fyk's overall properties, including the rapid dimming event and the rebrightening at late times. We also provide testable predictions for the behavior of the accretion flow in the future: if the second encounter was also a partial disruption then we predict another strong dimming event around day 1800 (August 2023), and a subsequent rebrightening around day 2400 (March 2025). This source provides strong evidence of the partial disruption of a star by a SMBH. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.07538v2

The rebrightening of AT2018fyk as a repeating partial tidal disruption event by T. Wevers et al. on Sunday 18 September Stars that interact with supermassive black holes (SMBHs) can either be completely or partially destroyed by tides. In a partial tidal disruption event (TDE) the high-density core of the star remains intact, and the low-density, outer envelope of the star is stripped and feeds a luminous accretion episode. The TDE AT2018fyk, with an inferred black hole mass of $10^{7.7pm0.4}$ M$_{odot}$, experienced an extreme dimming event at X-ray (factor of $>$6000) and UV (factor $sim$15) wavelengths $sim$500--600 days after discovery. Here we report on the re-emergence of these emission components roughly 1200 days after discovery. We find that the source properties are similar to those of the pre-dimming accretion state, suggesting that the accretion flow was rejuvenated to a similar state. We propose that a repeating partial TDE, where the partially disrupted star is on a $sim 600$ day orbit about the SMBH and is periodically stripped of mass during each pericenter passage, powers its unique lightcurve. This scenario provides a plausible explanation for AT2018fyk's overall properties, including the rapid dimming event and the rebrightening at late times. We also provide testable predictions for the behavior of the accretion flow in the future: if the second encounter was also a partial disruption then we predict another strong dimming event around day 1800 (August 2023), and a subsequent rebrightening around day 2400 (March 2025). This source provides strong evidence of the partial disruption of a star by a SMBH. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.07538v1

A simple and accurate prescription for the tidal disruption radius of a star and the peak accretion rate in tidal disruption events by Eric R. Coughlin et al. on Sunday 11 September A star destroyed by a supermassive black hole (SMBH) in a tidal disruption event (TDE) enables the study of SMBHs. We propose that the distance within which a star is completely destroyed by a SMBH, defined $r_{rm t, c}$, is accurately estimated by equating the SMBH tidal field (including numerical factors) to the maximum gravitational field in the star. We demonstrate that this definition accurately reproduces the critical $beta_{rm c} = r_{rm t}/r_{rm t, c}$, where $r_{rm t} = R_{star}left(M_{bullet}/M_{star}right)^{1/3}$ is the standard tidal radius with $R_{star}$ and $M_{star}$ the stellar radius and mass and $M_{bullet}$ the SMBH mass, for multiple stellar progenitors at various ages, and can be reasonably approximated by $beta_{rm c} simeq left[rho_{rm c}/(4rho_{star})right]^{1/3}$, where $rho_{rm c}$ ($rho_{star}$) is the central (average) stellar density. We also calculate the peak fallback rate and time at which the fallback rate peaks, finding excellent agreement with hydrodynamical simulations, and also suggest that the partial disruption radius -- the distance at which any mass is successfully liberated from the star -- is $beta_{rm partial} simeq 4^{-1/3} simeq 0.6$. For given stellar and SMBH populations, this model yields, e.g., the fraction of partial TDEs, the peak luminosity distribution of TDEs, and the number of directly captured stars. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.03982v1

BASS XXXVI: Constraining the Local Supermassive Black Hole - Halo Connection with BASS DR2 AGN by M. C. Powell et al. on Wednesday 07 September We investigate the connection between supermassive black holes (SMBHs) and their host dark matter halos in the local universe using the clustering statistics and luminosity function of AGN from the Swift/BAT AGN Spectroscopic survey (BASS DR2). By forward-modeling AGN activity into snapshot halo catalogs from N-body simulations, we test a scenario in which SMBH mass correlates with dark matter (sub)halo mass for fixed stellar mass. We compare this to a model absent of this correlation, where stellar mass alone determines the SMBH mass. We find that while both simple models are able to largely reproduce the abundance and overall clustering of AGN, the model in which black hole mass is tightly correlated with halo mass is preferred by the data by $1.8sigma$. When including an independent measurement on the black hole mass-halo mass correlation, this model is preferred by $4.6sigma$. We show that the clustering trends with black hole mass can further break the degeneracies between the two scenarios, and that our preferred model reproduces the measured clustering differences on 1-halo scales between large and small black hole masses. These results indicate that the halo binding energy is fundamentally connected to the growth of supermassive black holes. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.02728v1

Ultramassive black holes formed by triple quasar mergers at z sim 2 by Yueying Ni et al. on Wednesday 07 September The origin of rare and elusive ultramassive black holes (UMBH, with MBH > 1e10 Msun) is an open question. Using the large volume cosmological hydrodynamic simulation ASTRID, we report on the formation of an extremely massive UMBH with MBH ~ 1e11 Msun at z~2. The UMBH is assembled as a result of two successive mergers of massive galaxies each with stellar mass M* > 3e11 Msun that also produces a bright, rare triple quasar system powered by three ~10^9 Msun black holes. The second merger of supermassive black holes (SMBHs) follows the first after 150 Myrs. The merger events lead to sustained Eddington accretion onto the central SMBH, forming an UMBH in the center of a massive compact stellar core with M* > 2e12 Msun. The strong feedback of the UMBH quenches the surrounding star formation to < 10 Msun/yr in the inner 50 kpc/h region. There are two more UMBHs with MBH > 5e10 Msun at z>2 in ASTRID which are also produced by major mergers of galaxies, and their progenitors can be observed as quasar triplets of lower luminosity. The rarely observed quasar multiples can be the cradle of UMBHs at high redshift, and likely end up in the center of the most massive clusters. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.01249v2

http://spacescoop.org/en/scoops/2111/an-ancient-stormy-black-hole/ In the very distant past, 13.1 billion years ago, a supermassive black hole, they're called SMBHs for short, spewed a humongous amount of galactic wind.    It's a gigantic flow of gas that blew away the material that forms stars, also called ISM or interstellar medium, the stuff between stars.    Stormy, indeed! The Universe is about 13.8 billion years old, so this happened really close to the Big Bang, when the Universe was only 700 million years old.   We've added a new way to donate to 365 Days of Astronomy to support editing, hosting, and production costs.  Just visit: https://www.patreon.com/365DaysOfAstronomy and donate as much as you can! Share the podcast with your friends and send the Patreon link to them too!  Every bit helps! Thank you! ------------------------------------ Do go visit http://astrogear.spreadshirt.com/ for cool Astronomy Cast and CosmoQuest t-shirts, coffee mugs and other awesomeness! http://cosmoquest.org/Donate This show is made possible through your donations.  Thank you! (Haven't donated? It's not too late! Just click!) The 365 Days of Astronomy Podcast is produced by Astrosphere New Media. http://www.astrosphere.org/ Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org.

https://youtu.be/iI8GEpNcfsI Host: Fraser Cain ( @fcain )Special Guest: This week we are very pleased to welcome Dr. Jane Shevtsov, Mathematical Biology Instructor at UCLA, to the WSH. Her project proposal, Making Soil for Space Habitats by Seeding Asteroids with Fungi, is one of NASA's 2021 NIAC Phase I selections. Originally from Ukraine (which was then part of the Soviet Union), Jane and her family came to the United States when she was 7. She grew up in Los Angeles, and later earned a BS in Ecology, Behavior, and Evolution from UCLA in 2005. In 2021 she earned her PhD in Systems Ecology from the University of Georgia. In her spare time, Jane is an avid reader and enjoys rock wall climbing. To learn more about her NIAC proposal, visit the project's NASA webpage (https://www.nasa.gov/.../Making_Soil_for_Space_Habitats/) Regular Guests: Dr. Brian Koberlein ( https://briankoberlein.com/ & @BrianKoberlein ) Chris Carr ( @therealccarr ) Pam Hoffman ( http://spacer.pamhoffman.com/ & http://everydayspacer.com/ & @EverydaySpacer ) This week's stories: - The largest rotating objects in the Universe. - SMBHs blowing winds early. - Everything in the summer skies.   We've added a new way to donate to 365 Days of Astronomy to support editing, hosting, and production costs. Just visit: https://www.patreon.com/365DaysOfAstronomy and donate as much as you can! Share the podcast with your friends and send the Patreon link to them too! Every bit helps! Thank you! ------------------------------------ Do go visit http://astrogear.spreadshirt.com/ for cool Astronomy Cast and CosmoQuest t-shirts, coffee mugs and other awesomeness! http://cosmoquest.org/Donate This show is made possible through your donations. Thank you! (Haven't donated? It's not too late! Just click!) The 365 Days of Astronomy Podcast is produced by Astrosphere New Media. http://www.astrosphere.org/ Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org.

Help us make Syzygy even better! Tell your friends and give us a review, or show your support on Patreon: patreon.com/syzygypodSyzygy is produced by Chris Stewart and co-hosted by Dr Emily Brunsden from the Department of Physics at the University of York.On the web: syzygy.fm | Twitter: @syzygypodThings we talked about in this episode:Hyabusa-2 missionThe Supermassive Black Hole paper and press releaseA good article about the researchAll about SMBHs

Active Galactic Nuclei (AGN) are the accreting super massive black hole (SMBH) at the center of massive galaxies. The tight M-σ and M_BH-M_bulge correlations reveal that the host galaxies are affected by the effects of the SMBHs. In addition, many works studying on the rest-frame color-magnitude relation have shown that AGN host galaxies have intermediate colors, which are considered as a transition from the blue cloud to red sequence in host-galaxy color evolution. Some works interpreted this result as an evidence for the AGN feedback, in the sense that the accretion process not only builds up the massive black holes, but also has a powerful influence on the surrounding environment, triggering or suppressing the star-forming activity in the host galaxy. These correlations make obvious the need to investigate AGN-host coevolution. One way to understand this coevolution is to study the AGN duty cycle (i.e., the time scale that the SMBH is active), which can be obtained by estimating AGN population among all the galaxies through cosmic times. Such demographic studies require a well-sampled census and accurate redshift information. In particular at high redshift, objects are extremely faint and sample numbers are very small. This could cause large statistical errors. For example, Aird et al. (2010) argued that luminosity-dependent density evolution with a flattening faint-end slope of the X-ray luminosity function (XLF) at z > 1.2 may result from catastrophic photo-z failures caused by observational limitations and improper templates used for photo-z computation. However, spectroscopic redshifts are time-consuming and difficult to be obtained for faint sources at high redshifts. Therefore we have to rely on photometric redshifts (photo-z) techniques which need to be tuned specifically to be reliable for AGNs (i.e., proper magnitude priors, appropriate AGN-galaxy hybrid template for SED-fitting, and correct multi-wavelength counterparts). In recent years, many deep and high-resolution observations become available in multiple wavebands, specially at near/mid-infrared. This allows us to reach higher redshift, and make more accurate analysis on the multi-wavelength properties of AGNs. In this thesis, we focus on the ECDFS area which comprise also the GOODS-S and CDFS regions. This is the portion of the sky with the deepest and most complete photometric information from X-ray to radio, including intermediate bands from the Subaru telescope, and optical/near-infrared data from the Hubble space telescope. To compute accurate photo-z using these data, first we combined multi-wavelength catalogs from UV to infrared after the astrometric calibration and correction for the different methods of flux extraction (e.g., total fluxes, flux apertures and PSF- fitted photometry). Second we identified the best multi-wavelength counterparts for X-ray sources from the 4Ms-CDFS and 250ks-ECDFS surveys, taking into account the positional errors and multiple magnitude distributions as priors simultaneously. We found that more then 96% of X-ray sources have multi-wavelength counterparts. Thirdly we built a new library of active galactic nuclei/galaxy hybrid templates appropriate for the faint X-ray population in the CDFS to simulate the AGN spectral energy distribution from low to high redshift. For X-ray-selected AGNs, we achieved a photo-z accuracy of 0.013 with an outliers fraction of 5.3%, while for non-X-ray galaxies, the photo-z accuracy is 0.010 with an outlier fraction of 4.6%. With the SED-fitting results of our well-trained AGN-galaxy hybrids, we further studied the galaxy and AGN host properties via the rest-frame color-magnitude diagram (CMD) which is an useful probe to trace the stellar populations. We made corrections for dust extinction and/or AGN contamination for the galaxy/AGN host colors in the CANDELS/GOODS-S region. We found that the AGN host colors also present bimodality in the CMD up to z~2.5 as found in normal galaxies, and the position of the blue peaks in the AGN samples are almost constant with cosmic time. This implies a weak connection between AGN activity and star formation in the host galaxy. For the X-ray sources in the 4Ms-CDFS survey, we found that for most of the sources, the correction for dust extinction is larger than the correction for the AGN contribution. This is because the AGN population in this field is dominated by low-luminosity AGNs which have host-dominated SEDs. However for few bright sources, their host colors are strongly effected by AGN contribution rather than by the dust extinction. For these sources, the correction for AGN contribution is about two times larger than the correction for dust extinction in general. Therefore AGN/galaxy decomposition becomes more important in a shallower and wider X-ray surveys, e.g., XMM-COSMOS and eROSITA, which contains a larger fraction of bright AGNs. Furthermore, with our accurate redshifts for galaxies and AGNs, we defined a high-redshift (high-z) sample using the redshift probability distribution function P(z) rather than relying on the best-fit value of photo-z. We integrated P(z) within a given redshift range to obtain the photo-z probability in that range and selected high-z sources above a given threshold. When computing the number of sources in a given redshift range, each source will not be counted as "1" but as the proportion of it. We compared this P(z) technique with traditional color techniques adopted for galaxy evolutionary stages, like the Lyman break galaxy and the BzK color-color selection via sample completeness and purity. We found that the P(z) technique is the most efficient and reliable method for selecting high-z sources. This is not surprising as it makes use of photometric information from the entire SED rather than using only three photometric points. Lastly, we built a high-z (z > 3) sources list for X-ray sources in ECDFS region, and compared our list with previous work. In our work, we made better X-ray-to-optical/NIR associations considering the positional errors and magnitude distribution. In addition, we obtained accurate photo-z using well-established AGN-galaxy hybrids for X-ray selected AGNs and applied P(z) for each source. These procedures help improving on our high-z sample selection.

This work is focused on the search for intermediate-mass black holes (IMBHs) in the centers of globular clusters. It has been demonstrated that supermassive black holes (SMBHs) at the centers of galaxies show a tight correlation between their mass (M•) and the velocity dispersion (σ) of the galaxy. Investigating this M• − σ and similar correlations is crucial to constrain scenarios of galaxy formation and evolution. If they formed by runaway collisions of massive stars in young and dense stellar clusters, IMBHs could still be present in the centers of globular clusters, today. We measured the inner kinematic profiles for a sample of 9 galactic globular clusters using integral-field spectroscopy and combined them with existing outer kinematics and photom- etry obtained form HST archive images. In order to constrain the mass of a possible black hole we applied analytical Jeans models in combinations with varying M/LV profiles to each of the clusters. The results of these fits range from strong hints towards an IMBH (e.g. NGC 6388) to globular clusters which do not show any indications of a rising velocity dis- persion profile in their center (e.g. NGC 2808). Furthermore, the discovery of two high velocity stars in NGC 2808 opened another opportunity to study the internal kinematics of this particular cluster and indicates a high number of stellar-mass black holes in NGC 2808. We finally combined our results with measurements from the literature and investigated known scaling relations for SMBHs in galaxies (e.g. M• − σ) at the low-mass end by plac- ing the results and upper limits of IMBH measurements on these correlations. We found that IMBHs follow similar, but more shallow correlations of their mass and the properties of their host systems. This might be caused with the severe mass-loss the cluster suffers during its life time. In addition we ran numerical N-body simulations and compared globular clusters with dif- ferent black-hole retention fractions, IMBH masses and binary fractions. We found that IMBHs lead to a higher ejection rate of massive stars so that clusters with less depleted mass functions might therefore be good candidates to host IMBHs at their centers. In the future more N-body simulations will be performed in order to reproduce our observations in a more sophisticated way and perform crucial tests to our observing and analysis methods. The search for IMBHs requires both high spatial and spectral resolution and will remain at the edge of feasibility. However, it is crucial to continue the investigations in order to shed light on black-hole formation and growth.

Studies have suggested that there is a strong correlation between the masses of nuclear star clusters (NSCs) and their host galaxies, a correlation which is said to be an extension of the well-known correlations between supermassive black holes (SMBHs) and their host galaxies. But careful analysis of disk galaxies-including 2D bulge/disk/bar decompositions-shows that while SMBHs correlate with the stellar mass of the bulge component of galaxies, the masses of NSCs correlate much better with the total galaxy stellar mass. In addition, the mass ratio M-NSC/M-star,M- tot for NSCs in spirals (at least those with Hubble types Sc and later) is typically an order of magnitude smaller than the mass ratio M-BH/M-star,M- bul of SMBHs. The absence of a universal ``central massive object'' correlation argues against common formation and growth mechanisms for both SMBHs and NSCs. We also discuss evidence for a break in the NSC-host galaxy correlation, galaxies with Hubble types earlier than Sbc appear to host systematically more massive NSCs than do types Sc and later.

Lots of galaxies have SMBHs at their centres. Coincidence?