Growth Of Supermassive Black Holes Research Articles

The high energy X-ray probe (HEX-P): the future of hard X-ray dual AGN science

A fundamental goal of modern-day astrophysics is to understand the connection between supermassive black hole (SMBH) growth and galaxy evolution. Merging galaxies offer one of the most dramatic channels for galaxy evolution known, capable of driving inflows of gas into galactic nuclei, potentially fueling both star formation and central SMBH activity. Dual active galactic nuclei (dual AGNs) in late-stage mergers with nuclear pair separations <10 kpc are thus ideal candidates to study SMBH growth along the merger sequence since they coincide with the most transformative period for galaxies. However, dual AGNs can be extremely difficult to confirm and study. Hard X-ray (>10 keV) studies offer a relatively contamination-free tool for probing the dense obscuring environments predicted to surround the majority of dual AGN in late-stage mergers. To date, only a handful of the brightest and closest systems have been studied at these energies due to the demanding instrumental requirements involved. We demonstrate the unique capabilities of HEX-P to spatially resolve the soft and - for the first time - hard X-ray counterparts of closely-separated (∼2″−5″) dual AGNs in the local Universe. By incorporating physically-motivated obscuration models, we reproduce realistic broadband X-ray spectra expected for deeply embedded accreting SMBHs. Hard X-ray spatially resolved observations of dual AGNs—accessible only to HEX-P—will hence transform our understanding of dual AGN in the nearby Universe.

The evolution of supermassive black hole mass–bulge mass relation by a semi-analytical model, ν2GC

ABSTRACT We have investigated the redshift evolution of the relationship between supermassive black hole (SMBH) mass and host bulge mass using a semi-analytical galaxy formation model ν2GC. Our model reproduces the relation in the local universe well. We find that, at high redshift (z ≳ 3), two sequences appear in the SMBH mass–bulge mass plane. The emergence of these two sequences can be attributed to the primary triggers of the growth of the SMBHs and bulges: galaxy mergers and disc instabilities. The growth of SMBHs and bulges as a result of galaxy mergers is responsible for giving rise to the high-mass sequence, in which SMBHs are more massive for a given host bulge mass than in the low-mas sequence. Conversely, disc instabilities are accountable for the emergence of the low-mass sequence. At lower redshifts, galaxy mergers tend to become increasingly deficient in gas, resulting in a preferential increase of bulge mass without a corresponding growth in SMBH mass. This has the effect of causing galaxies in the upper sequence to shift towards the lower one on the SMBH mass–bulge mass plane. The galaxies that undergo dry mergers serve to bridge the gap between the two sequences, eventually leading to convergence into a single relation known in the local universe. Our results suggest that the observations of the SMBH mass–bulge mass relation in high redshifts can provide insight into their growth mechanisms.

Star Formation and Dust in the Cosmic Web

The large-scale environment of the cosmic web is believed to impact galaxy evolution, but there is still no consensus regarding the mechanisms. We use a semi-analytic model (SAM) galaxy catalog to study the star formation and dust content of local galaxies in different cosmic environments of the cosmic web—namely voids, filaments, walls, and nodes. We find a strong impact of the environment only for galaxies with M stars ≲ 1010.8 M ⊙: the less dense the environment, the larger the star formation rate and dust content at fixed stellar mass. This is attributed to the fact that galaxies in less dense environments typically feature younger stellar populations, a slower evolution of their stellar mass, and delayed star formation compared to galaxies in denser environments. As for galaxies with M stars ≳ 1010.8 M ⊙, the differences among environments are milder, due to the disk-instability-driven supermassive black hole (SMBH) growth implemented in the SAM, which makes SMBH growth, and thus galaxy quenching, environment-insensitive. We qualitatively test our predictions against observations by identifying environments in Sloan Digital Sky Survey Data Release 16 using dust masses derived from the GAMA survey. The agreement is encouraging, particularly at logMstars/M⊙≳10.5–11 , where the specific star formation rates and dust masses appear quite environment-insensitive. This result confirms the importance of in situ growth channels of SMBHs.

Overmassive Black Holes at Cosmic Noon: Linking the Local and the High-redshift Universe

We report for the first time a sample of 12 supermassive black holes (SMBHs) hosted by low-mass galaxies at cosmic noon, i.e., in a redshift range consistent with the peak of star formation history: z ∼ 1–3. These black holes are 2 orders of magnitude too massive for the stellar content of their hosts when compared with the local relation for active galaxies. These overmassive systems at cosmic noon share similar properties with the high-z sources found ubiquitously in recent James Webb Space Telescope (JWST) surveys (same range of black-hole-to-stellar-mass ratio, bolometric luminosity, and Eddington ratio). We argue that black hole feedback processes, for which there is possible evidence in five of the sources, and the differing environments in galactic nuclei at these respective epochs play a key role in these overmassive systems. These findings contribute to our understanding of the growth and coevolution of SMBHs and their host galaxies across cosmic time, offering a link between the early Universe (z > 4) observed by JWST and observations of the present-day Universe (z ≲ 1).

Heavily obscured AGN detection: A radio versus X-ray challenge

In the supermassive black hole (SMBH)-galaxy coevolution scenario, heavily obscured active galactic nuclei (AGN) represent a fundamental phase of SMBH growth during which most of the BH mass is accreted and the scaling relations with the host galaxy are set. Obscured nuclei are thought to constitute a major fraction of the whole AGN population, but their statistics and evolution across cosmic time are still highly uncertain. Therefore, it is pivotal to identify new ways to detect this vast and hidden population of growing SMBHs. A promising way to select heavily obscured AGN is through radio emission, which is largely unaffected by obscuration and can be used as a proxy for nuclear activity. In this work, we study the AGN radio detection effectiveness in the major deep extragalactic surveys, considering different AGN obscuration levels, redshift, and AGN bolometric luminosities. We particularly focus on comparing their radio and X-ray detectability, making predictions for present and future radio surveys. We extrapolated the predictions of the AGN population synthesis model of the cosmic X-ray background (CXB) to the radio band, by deriving the 1.4 GHz luminosity functions of unobscured (i.e., with hydrogen column densities $ H <22$), obscured ($22< H <24$), and Compton-thick (CTK, $ H >24$) AGN. We then used these functions to forecast the number of detectable AGN based on the area, flux limit, and completeness of a given radio survey and compare it with the AGN number resulting from X-ray predictions. When applied to deep extragalactic fields covered both by radio and X-ray observations, we show that, while X-ray selection is generally more effective in detecting unobscured AGN, the surface density of CTK AGN radio detected is on average ten times larger than the X-ray one, and even greater at high redshifts, considering the current surveys and facilities. Our results suggest that thousands of CTK AGN are already present in current radio catalogs, but most of them escaped any detection in the corresponding X-ray observations. We also present expectations for the number of AGN to be detected by the Square Kilometer Array Observatory (SKAO) in its future deep and wide radio continuum surveys, finding that it will be able to detect more than 2000 AGN at $z>6$ and tens of them at $z>10$, more than half of which are expected to be CTK.

A spectacular galactic scale magnetohydrodynamic powered wind in ESO 320-G030

How galaxies regulate nuclear growth through gas accretion by supermassive black holes (SMBHs) is one of the most fundamental questions in galaxy evolution. One potential way to regulate nuclear growth is through a galactic wind that removes gas from the nucleus. It is unclear whether galactic winds are powered by jets, mechanical winds, radiation, or via magnetohydrodynamic (MHD) processes. Compact obscured nuclei represent a significant phase of galactic nuclear growth. These galaxies hide growing SMBHs or unusual starbursts in their very opaque, extremely compact (r < 100 pc) centres. They are found in approximately 30% of the luminous and ultra-luminous infrared galaxy population. Here, we present high-resolution ALMA observations (∼30 mas, ∼5 pc) of ground-state and vibrationally excited HCN towards ESO 320-G030 (IRAS 11506-3851). ESO 320-G030 is an isolated luminous infrared galaxy known to host a compact obscured nucleus and a kiloparsec-scale molecular wind. Our analysis of these high-resolution observations excludes the possibility of a starburst-driven wind, a mechanically or energy driven active galactic nucleus wind, and exposes a molecular MDH wind. These results imply that the nuclear evolution of galaxies and the growth of SMBHs are similar to the growth of hot cores or protostars where gravitational collapse of the nuclear torus drives a MHD wind. These results mean galaxies are capable, in part, of regulating the evolution of their nuclei without feedback.

Mapping the Growth of Supermassive Black Holes as a Function of Galaxy Stellar Mass and Redshift

The growth of supermassive black holes is strongly linked to their galaxies. It has been shown that the population mean black hole accretion rate ( BHAR¯ ) primarily correlates with the galaxy stellar mass (M ⋆) and redshift for the general galaxy population. This work aims to provide the best measurements of BHAR¯ as a function of M ⋆ and redshift over ranges of 109.5 < M ⋆ < 1012 M ⊙ and z < 4. We compile an unprecedentedly large sample with 8000 active galactic nuclei (AGNs) and 1.3 million normal galaxies from nine high-quality survey fields following a wedding cake design. We further develop a semiparametric Bayesian method that can reasonably estimate BHAR¯ and the corresponding uncertainties, even for sparsely populated regions in the parameter space. BHAR¯ is constrained by X-ray surveys sampling the AGN accretion power and UV-to-infrared multiwavelength surveys sampling the galaxy population. Our results can independently predict the X-ray luminosity function (XLF) from the galaxy stellar mass function (SMF), and the prediction is consistent with the observed XLF. We also try adding external constraints from the observed SMF and XLF. We further measure BHAR¯ for star-forming and quiescent galaxies and show that star-forming BHAR¯ is generally larger than or at least comparable to the quiescent BHAR¯ .

The high energy X-ray probe (HEX-P): constraining supermassive black hole growth with population spin measurements

Constraining the primary growth channel of supermassive black holes (SMBHs) remains one the most actively debated questions in the context of cosmological structure formation. Owing to the expected connection between SMBH spin parameter evolution and the accretion and merger history of individual black holes, population spin measurements offer a rare observational window into the cosmic growth of SMBHs. As of today, the most common method for estimating SMBH spin relies on modeling the relativistically broaden atomic profiles in the reflection spectrum observed in X-rays. In this paper, we study the observational requirements needed to confidently distinguish between the primary SMBH growth channels based on their distinct spin-mass distributions predicted by the Horizon-AGN cosmological simulation. Indoing so, we characterize outstanding limitations associated with the existing measurements and discuss the landscape of future observational campaigns which could be planned and executed with future X-ray observatories. We focus our attention on the High-Energy X-ray Probe (HEX-P), a proposed probe-class mission designed to serve the high-energy community in the 2030s.

Spectroscopic Confirmation of Obscured AGN Populations from Unsupervised Machine Learning

We present the result of a spectroscopic campaign targeting active galactic nucleus (AGN) candidates selected using a novel unsupervised machine-learning (ML) algorithm trained on optical and mid-infrared photometry. AGN candidates are chosen without incorporating prior AGN selection criteria and are fainter, redder, and more numerous, ∼340 AGN deg−2, than comparable photometric and spectroscopic samples. In this work, we obtain 178 rest-optical spectra from two candidate ML-identified AGN classes with the Hectospec spectrograph on the MMT Observatory. We find that our first ML-identified group is dominated by Type I AGNs (85%) with a <3% contamination rate from non-AGNs. Our second ML-identified group is mostly comprised of Type II AGNs (65%), with a moderate contamination rate of 15% primarily from star-forming galaxies. Our spectroscopic analyses suggest that the classes recover more obscured AGNs, confirming that ML techniques are effective at recovering large populations of AGNs at high levels of extinction. We demonstrate the efficacy of pairing existing WISE data with large-area and deep optical/near-infrared photometric surveys to select large populations of AGNs and recover obscured growth of supermassive black holes. This approach is well suited to upcoming photometric surveys, such as Euclid, Rubin, and Roman.

The high energy X-ray probe (HEX-P): bringing the cosmic X-ray background into focus

Since the discovery of the cosmic X-ray background (CXB), astronomers have strived to understand the accreting supermassive black holes (SMBHs) contributing to its peak in the 10–40 keV band. Existing soft X-ray telescopes could study this population up to only 10 keV, and, while NuSTAR (focusing on 3–24 keV) made great progress, it also left significant uncertainties in characterizing the hard X-ray population, crucial for calibrating current population synthesis models. This paper presents an in-depth analysis of simulations of two extragalactic surveys (deep and wide) with the High-Energy X-ray Probe (HEX-P), each observed for 2 Ms. Applying established source detection techniques, we show that HEX-P surveys will reach a flux of ∼10−15 erg s−1 cm−2 in the 10–40 keV band, an order of magnitude fainter than current NuSTAR surveys. With the large sample of new hard X-ray detected sources (∼2000), we showcase HEX-P’s ability to resolve more than 80% of the CXB up to 40 keV into individual sources. The expected precision of HEX-P’s resolved background measurement will allow us to distinguish between population synthesis models of SMBH growth. HEX-P will leverage accurate broadband (0.5–40 keV) spectral analysis and the combination of soft and hard X-ray colors to provide obscuration constraints even for the fainter sources, with the overall objective of measuring the Compton-thick fraction. With unprecedented sensitivity in the 10–40 keV band, HEX-P will explore the hard X-ray emission from AGN to flux limits never reached before, thus expanding the parameter space for serendipitous discoveries. Consequently, it is plausible that new models will be needed to capture the population HEX-P will unveil.

Observational properties of active galactic nucleus obscuration during the peak of accretion growth

ABSTRACT We investigated the gas obscuration and host galaxy properties of active galactic nuclei (AGNs) during the peak of cosmic accretion growth of supermassive black holes at redshift 0.8–1.8 using X-ray-detected AGNs with mid-infrared and far-infrared detection. The sample was classified as type-1 and type-2 AGNs using optical spectral and morphological classification while the host galaxy properties were estimated with multiwavelength spectral energy distribution fitting. For type-1 AGNs, the black hole mass was determined from MgII emission lines while the black hole mass of type-2 AGNs was inferred from the host galaxy’s stellar mass. Based on the derived parameters, the distribution of the sample in the absorption hydrogen column density (NH) versus Eddington ratio diagram is examined. Among the type-2 AGNs, 28 ± 5 per cent are in the forbidden zone, where the obscuration by dust torus cannot be maintained due to radiation pressure on dusty material. The fraction is higher than that observed in the local universe from the Burst Alert Telescope AGN Spectroscopic Survey data release 2 (BASS DR2) (11 ± 3 per cent). The higher fraction implies that the obscuration of the majority of AGNs is consistent with the radiation pressure regulated unified model but with an increased incidence of interstellar matter (ISM)-obscured AGNs. We discuss the possibility of dust-free absorption in type-1 AGNs and heavy ISM absorption in type-2 AGNs. We also find no statistical difference in the star-formation activity between type-1 and type-2 AGNs which may suggest that obscuration triggered by a gas-rich merging is not common among X-ray detected AGNs in this epoch.

Formation and growth of the first supermassive black holes in MOG

The emergence of supermassive black holes (SMBHs) in the early universe remains a topic of profound interest and debate. In this paper, we investigate the formation and growth of the first SMBHs within the framework of Modified Gravity (MOG), where gravity exhibits increased strength. We explore how MOG, as an alternative to the standard model, may offer novel insights into the emergence of SMBHs and potentially reconcile the discrepancies observed in the accretion and growth processes. We examine the dynamics of gas and matter in this modified gravitational framework, shedding light on the unique interplay between gravity and the formation of SMBHs.

The dark balance: quantifying the inner halo response to active galactic nuclei feedback in galaxies

ABSTRACT This paper presents a study of the impact of supermassive black hole (SMBH) feedback on dark matter (DM) haloes in numerical NIHAO (Numerical Investigation of a Hundred Astrophysical Object) simulations of galaxies. In particular, the amount of DM displaced via active galactic nuclei (AGNs) feedback and the physical scale over which AGN feedback affects the DM halo are quantified by comparing NIHAO simulations with and without AGN feedback. NIHAO galaxies with log (M*/M⊙) ≥ 10.0 show a growing central DM suppression of 0.2 dex (∼40 per cent) from z = 1.5 to the present relative to no AGN feedback simulations. The growth of the DM suppression is related to the mass evolution of the SMBH and the gas mass in the central regions. For the most massive NIHAO galaxies with log (M*/M⊙) &amp;gt; 10.5, partially affected by numerical resolution, the central DM suppression peaks at z = 0.5 after which halo contraction overpowers AGN feedback due a shortage of gas and thus, SMBH growth. The spatial scale, or ‘sphere of influence’, over which AGN feedback affects the DM distribution decreases as a function of time for Milky Way-mass galaxies (from ∼16 kpc at z = 1.5 to ∼7.8 kpc at z = 0) as a result of halo contraction due to stellar growth. For the most massive NIHAO galaxies, the size of the sphere of influence remains constant (∼16 kpc) for z &amp;gt; 0.5 owing to the balance between AGN feedback and halo contraction.

Little Red Dots: An Abundant Population of Faint Active Galactic Nuclei at z ∼ 5 Revealed by the EIGER and FRESCO JWST Surveys

Characterizing the prevalence and properties of faint active galactic nuclei (AGNs) in the early Universe is key for understanding the formation of supermassive black holes (SMBHs) and determining their role in cosmic reionization. We perform a spectroscopic search for broad Hα emitters at z ≈ 4–6 using deep JWST/NIRCam imaging and wide field slitless spectroscopy from the EIGER and FRESCO surveys. We identify 20 Hα lines at z = 4.2–5.5 that have broad components with line widths from ∼1200–3700 km s−1, contributing ∼30%–90% of the total line flux. We interpret these broad components as being powered by accretion onto SMBHs with implied masses ∼107–8 M ⊙. In the UV luminosity range M UV,AGN+host = −21 to −18, we measure number densities of ≈10−5 cMpc−3. This is an order of magnitude higher than expected from extrapolating quasar UV luminosity functions (LFs). Yet, such AGN are found in only <1% of star-forming galaxies at z ∼ 5. The number density discrepancy is much lower when compared to the broad Hα LF. The SMBH mass function agrees with large cosmological simulations. In two objects, we detect complex Hα profiles that we tentatively interpret as caused by absorption signatures from dense gas fueling SMBH growth and outflows. We may be witnessing early AGN feedback that will clear dust-free pathways through which more massive blue quasars are seen. We uncover a strong correlation between reddening and the fraction of total galaxy luminosity arising from faint AGN. This implies that early SMBH growth is highly obscured and that faint AGN are only minor contributors to cosmic reionization.

Measuring the Virial Factor in SDSS DR7 Active Galactic Nuclei with Redshifted Hβ and Hα Broad Emission Lines

Under the hypothesis of gravitational redshift induced by the central supermassive black hole and based on line widths and shifts of redward-shifted Hβ and Hα broad emission lines for more than 8000 Sloan Digital Sky Survey DR7 active galactic nuclei (AGNs), we measure the virial factor in determining supermassive black hole masses. The virial factor had been believed to be independent of accretion radiation pressure on gas clouds in broad-line regions (BLRs) and only dependent on the inclination effects of BLRs. The virial factor measured spans a very large range. For the vast majority of AGNs (>96%) in our samples, the virial factor is larger than the f = 1 usually used in the literature. The f-correction makes the percent of high-accreting AGNs decrease by about 100 times. There are positive correlations of f with the dimensionless accretion rate and Eddington ratio. The redward shifts of Hβ and Hα are mainly of gravitational origin, confirmed by a negative correlation between the redward shift and the dimensionless radius of the BLR. Our results show that radiation pressure force is a significant contributor to the measured virial factor, containing the inclination effects of the BLR. The usually used values of f should be corrected for high-accreting AGNs, especially high-redshift quasars. The f-correction increases their masses by 1–2 orders of magnitude, which will make it more challenging to explain the formation and growth of supermassive black holes at high redshifts.

Identifying heavy stellar black holes at cosmological distances with next-generation gravitational-wave observatories

ABSTRACT We investigate the detectability of single-event coalescing black hole binaries with total mass of $100\!-\!600{\, {\rm {M}}_{\odot }}$ at cosmological distances (5 ≲ z ≲ 20) with the next generation of terrestrial gravitational wave observatories, specifically Einstein Telescope and Cosmic Explorer. Our ability to observe these binaries is limited by the low-frequency performance of the detectors. Higher order multipoles of the gravitational wave signal are observable in these systems, and detection of such multipoles serves to both extend the mass range over which black hole binaries are observable and improve the recovery of their individual masses and redshift. For high-redshift systems of $\sim 200 {\, {\rm {M}}_{\odot }}$ we will be able to confidently infer that the redshift is at least z = 12, and for systems of $\sim 400 {\, {\rm {M}}_{\odot }}$ we can infer a minimum redshift of at least z = 8. We discuss the impact that these observations will have in narrowing uncertainties on the existence of the pair-instability mass gap, and their implications on the formation of the first stellar black holes that could be seeds for the growth of supermassive black holes powering high-z quasars.

Evidence for episodic black hole growth of reionization-era quasars observed with Magellan/FIRE

ABSTRACT Observations of high-redshift quasars hosting billion solar mass black holes at z ≳ 6 challenge our understanding of early supermassive black hole (SMBH) growth. In this work, we conduct a near-infrared spectroscopic study of 19 quasars at 6.2 ≲ z ≲ 7.5, using the Folded-port InfraRed Echellette instrument on the 6.5-m Magellan/Baade Telescope. We estimate the single-epoch masses of the quasars’ SMBHs by means of the Mg ii emission line and find black hole masses of $M_{\text{BH}} \approx (0.2\!\!-\!\!4.8)\, \times \, 10^9\ \mathrm{ M}_\odot$. Furthermore, we measure the sizes of the quasars’ proximity zones, which are regions of enhanced transmitted flux bluewards of the Ly $\alpha \,$ emission line, ionized by the quasars’ radiation itself. While it has been shown that the proximity zone sizes correlate with the quasars’ lifetimes due to the finite response time of the intergalactic medium to the quasars’ radiation, we do not find any correlation between the proximity zone sizes and the black hole mass, which suggests that quasar activity and the concomitant black hole growth are intermittent and episodic.

Statistical study of a large and cleaned sample of ultraluminous and hyperluminous X-ray sources

Context. Ultraluminous and hyperluminous X-ray (ULX and HLX) sources could constitute interesting laboratories to further improve our understanding of the supermassive black hole growth through super-Eddington accretion episodes and successive mergers of lighter holes. ULXs are thought to be powered by super-Eddington accretion onto stellar-mass compact objects, while HLXs are of an unknown nature, but they could be good candidates for accreting intermediate mass black holes (IMBHs). However, a significant portion of the sample of ULX and HLX candidates derived from catalogue searches are in fact background active galactic nuclei (AGN). Aims. Here we build samples of ULXs and HLXs from the three largest X-ray catalogues available, compiled from XMM-Newton, Swift-XRT, and Chandra detections, and the GLADE catalogue containing 1.7 million galaxies at D &lt; 1000 Mpc. We aim to characterise the frequency, environment, hardness, and variability of ULXs and HLXs to better assess their differences and understand their populations. Methods. After a thorough classification of these X-ray sources, we were able to remove ∼42% of sources with a signal-to-noise ratio (S/N) &gt; 3 which were shown to be contaminants, to obtain the cleanest sample of ULXs and HLXs to date. From a sample of 1342 ULXs and 191 HLXs detected with a S/N &gt; 3σ, we study the occupation fraction, hardness, variability, radial distribution, and preferred environment of the sources. We built their Malmquist-corrected X-ray luminosity functions (XLFs) and compared them with previous studies. Thanks to the unprecedented size of the sample, we were able to statistically compare ULXs and HLXs and assess the differences in their nature. The interpretation of HLXs as IMBHs is investigated. Results. A significant break is seen in the XLF at ∼1040 erg s−1. With our ULX sample, containing ≲2% of contaminants, we are able to confirm that ULXs are located preferentially in spiral galaxies and galaxies with higher star formation rates. While X-ray binaries (XRBs), ULXs, and most HLXs share common hardness and variability distributions, a fraction of HLXs appear significantly softer. Unlike ULXs, HLXs seem to reside equally in spiral as well as lenticular and elliptical galaxies. We note that 35% of the HLX candidates have an optical counterpart, and we estimate the mass of 120 of them to be in the range of 2 × 103 − 105 M⊙. Most of the HLX population is found to be consistent with an accreting massive black hole in a dwarf galaxy satellite of the primary host. This diverse nature needs to be confirmed with deeper optical and infrared observations, as well as upcoming X-ray facilities.

Halo Mass-observable Proxy Scaling Relations and Their Dependencies on Galaxy and Group Properties

Based on the DECaLS shear catalog, we study the scaling relations between halo mass (M h) and various proxies for Sloan Digital Sky Survey central galaxies, including stellar mass (M *), stellar velocity dispersion (σ *), abundance-matching halo mass (M AM), and satellite velocity dispersion (σ s), and their dependencies on galaxy and group properties. In general, these proxies all have strong positive correlations with M h, consistent with previous studies. We find that the M h–M * and M h–σ * relations depend strongly on group richness (N sat), while the M h–M AM and M h–σ s relations are independent of it. Moreover, the dependence on the star formation rate (SFR) is rather weak in the M h–σ * and M h–σ s relations, but very prominent in the other two. σ s is thus the best proxy among them, and its scaling relation is in good agreement with hydrodynamical simulations. However, estimating σ s accurately for individual groups/clusters is challenging because of interlopers and the requirement for sufficient satellites. We construct new proxies by combining M *, σ *, and M AM, and find that the proxy with 30% contribution from M AM and 70% from σ * can minimize the dependence on N sat and the SFR. We obtain the M h–supermassive black hole (SMBH) mass relation via the SMBH scaling relation and find indications for rapid and linear growth phases for the SMBH. We also find that correlations among M h, M *, and σ * change with M *, indicating that different processes drive the growth of galaxies and SMBHs at different stages.

Probing supermassive black hole growth and its dependence on stellar mass and star formation rate in low-redshift galaxies

ABSTRACT We present an improved study of the relation between supermassive black hole growth and their host galaxy properties in the local Universe (z &amp;lt; 0.33). To this end, we build an extensive sample combining spectroscopic measurements of star formation rate (SFR) and stellar mass from Sloan Digital Sky Survey, with specific Black Hole accretion rate (sBHAR, $\lambda _{\mathrm{sBHAR}} \propto L_{\rm X}/\mathcal {M}_{\ast }$) derived from the XMM–Newton Serendipitous Source Catalogue (3XMM–DR8) and the Chandra Source Catalogue (CSC2.0). We find that the sBHAR probability distribution for both star-forming and quiescent galaxies has a power-law shape peaking at log λsBHAR ∼ −3.5 and declining towards lower sBHAR in all stellar mass ranges. This finding confirms the decrease of active galactic nucleus (AGN) activity in the local Universe compared to higher redshifts. We observe a significant correlation between $\log \, \lambda _{\rm sBHAR}$ and $\log \, {\rm SFR}$ in almost all stellar mass ranges, but the relation is shallower compared to higher redshifts, indicating a reduced availability of accreting material in the local Universe. At the same time, the BHAR-to-SFR ratio for star-forming galaxies strongly correlates with stellar mass, supporting the scenario where both AGN activity and stellar formation primarily depend on the stellar mass via fuelling by a common gas reservoir. Conversely, this ratio remains constant for quiescent galaxies, possibly indicating the existence of the different physical mechanisms responsible for AGN fuelling or different accretion mode in quiescent galaxies.