We present a study of the relationship between black hole accretion rate (BHAR) and star formation rate (SFR) in a sample of giant elliptical galaxies. These galaxies, which live at the centers of galaxy groups and clusters, have star formation and black hole activity that is primarily fueled by gas condensing out of the hot intracluster medium. For a sample of 46 galaxies spanning 5 orders of magnitude in BHAR and SFR, we find a mean ratio of log(BHAR/SFR) = -1.45 +/- 0.2, independent of the methodology used to constrain both SFR and BHAR. This ratio is significantly higher than most previously-published values for field galaxies. We investigate whether these high BHAR/SFR ratios are driven by high BHAR, low SFR, or a different accretion efficiency in radio galaxies. The data suggest that the high BHAR/SFR ratios are primarily driven by boosted black hole accretion in spheroidal galaxies compared to their disk counterparts. We propose that angular momentum of the cool gas is the primary driver in suppressing BHAR in lower mass galaxies, with massive galaxies accreting gas that has condensed out of the hot phase on nearly radial trajectories. Additionally, we demonstrate that the relationship between specific BHAR and SFR has much less scatter over 6 orders of magnitude in both parameters, due to competing dependence on morphology between the M_BH--M_* and BHAR--SFR relations. In general, active galaxies selected by typical techniques have sBHAR/sSFR ~ 10, while galactic nuclei with no clear AGN signatures have sBHAR/sSFR ~ 1, consistent with a universal M_BH--M_spheroid relation.
Isolated massive elliptical galaxies, or that are present at the center of cool-core clusters, are believed to be powered by hot gas accretion directly from their surrounding hot X-ray emitting gaseous medium. This leads to a giant Bondi-type spherical/quasi-spherical accretion flow onto their host SMBHs, with the accretion flow region extending well beyond the Bondi radius. In this work, we present a detailed study of Bondi-type spherical flow in the context of these massive ellipticals by incorporating the effect of entire gravitational potential of the host galaxy in the presence of cosmolo…
We present high-resolution, three-dimensional hydrodynamic simulations of the fueling of supermassive black holes in elliptical galaxies from a turbulent medium on galactic scales, taking M87* as a typical case. The simulations use a new GPU-accelerated version of the Athena++ AMR code, and span more than 6 orders of magnitude in radius, reaching scales similar to the black hole horizon. The key physical ingredients are radiative cooling and a phenomenological heating model. We find that the accretion flow takes the form of multiphase gas at radii less than about a kpc. The cold gas accretion …
Outbursts from active galactic nuclei (AGN) affect the hot atmospheres of isolated giant elliptical galaxies (gE's), as well as those in groups and clusters of galaxies. Chandra observations of a sample of nearby gE's show that the average power of AGN outbursts is sufficient to stop their hot atmospheres from cooling and forming stars, consistent with radio mode feedback models. The outbursts are intermittent, with duty cycles that increases with size.
How elliptical galaxies form is a key question in observational cosmology. While the formation of massive ellipticals is strongly linked to mergers, the low mass (Mstar < 10^9.5 MSun) regime remains less well explored. In particular, studying elliptical populations when they are blue, and therefore rapidly building stellar mass, offers strong constraints on their formation. Here, we study 108 blue, low-mass ellipticals (which have a median stellar mass of 10^8.7 MSun) at z < 0.3 in the COSMOS field. Visual inspection of extremely deep optical HSC images indicates that less than 3 per cent of t…
A model is proposed for the formation of gas-rich dwarf irregular galaxies and gas-poor, rotating dwarf elliptical galaxies following the interaction between two giant galaxies as a function of space density. The formation of dwarf galaxies is considered to depend on a random variable, the tidal index theta, an environmental parameter defined by Karachentsev et al. (2004), such that for theta less than zero, the formation of dwarf irregular galaxy is assured whereas for theta greater than zero, the formation of dwarf ellipticals is preferred. It is found that for particular ranges of the inter…
We present significantly improved measurements of turbulent velocities in the hot gaseous halos of nearby giant elliptical galaxies. Using deep XMM-Newton Reflection Grating Spectrometer (RGS ) observations and a combination of resonance scattering and direct line broadening methods, we obtain well bounded constraints for 13 galaxies. Assuming that the turbulence is isotropic, we obtain a best fit mean 1D turbulent velocity of ~110 km/s. This implies a typical 3D Mach number ~0.45 and a typical non-thermal pressure contribution of ~6 per cent in the cores of nearby massive galaxies. The intrin…
The most evident features of colour-magnitude diagrams of galaxies are the red sequence of quiescent galaxies, extending up to the brightest elliptical galaxies, and the blue cloud of star-forming galaxies, which is truncated at a luminosity L~L*. The truncation of the blue cloud indicates that in the most massive systems star formation must be quenched. For this to happen the virial-temperature galactic gas must be kept hot and any accreted cold gas must be heated. The elimination of accreted cold gas can be due to thermal evaporation by the hot interstellar medium, which in turn is prevented…
We present hydrodynamical N-body models which demonstrate that elliptical galaxies can transform into S0s by acquiring a disc. In particular, we show that the merger with a massive gas-rich satellite can lead to the formation of a baryonic disc around an elliptical. We model the elliptical as a massive, compact galaxy which could be observed as a 'red nugget' in the high-z universe. This scenario contrasts with existing S0 formation scenarios in the literature in two important ways. First, the progenitor is an elliptical galaxy whereas scenarios in the literature typically assume a spiral prog…
An Orbital Interpretation of Decreasing Galaxy Velocity Distance Relations in Systems Dominated by Giant Elliptical Galaxies
Abdelhamid Ibn Badis University（阿卜杜勒哈米德·伊本·巴迪斯大学）；Elaboration and Characterization Physico-Mechanical and Metallurgical of Materials Laboratory (ECP3M), Abdelhamid Ibn Badis University-Mostaganem（阿卜杜勒哈米德·伊本·巴迪斯大学-穆斯塔加奈姆物理机械与冶金材料表征与制备实验室）；University of Relizane（赖利赞大学）
Globular clusters (GCs) are thought to be ancient relics from the early formative phase of galaxies, although their physical origin remains uncertain. GCs are most numerous around massive elliptical galaxies, where they can exhibit a broad colour dispersion, suggesting a wide metallicity spread. Here, we show that many thousands of compact and massive (~5$\times$10$^{\rm 3}-$3$\times$ 10$^{\rm 6} M_{\odot}$) star clusters have formed at an approximately steady rate over, at least, the past ~1Gyr around NGC 1275, the central giant elliptical galaxy of the Perseus cluster. Beyond ~1Gyr, these st…
Massive starforming regions like Giant HII Regions (GHIIR) and HII Galaxies (HIIG) are emission line systems ionized by compact young massive star clusters (YMC) with masses ranging from $10^4$M$_\odot$ to $10^8$M$_\odot$. We model the photometric and dynamical evolution over a Hubble time of the massive gravitationally bound systems that populate the tight relation between absolute blue magnitude and velocity dispersion ($M_{B}-σ$) of GHIIR and HIIG and compare the resulting relation with that one of old stellar systems: globular clusters, elliptical galaxies, bulges of spirals. After 12~Gyr …
Recent observations have found extended multi-phase gas in a significant fraction of massive elliptical galaxies. We perform high-resolution three-dimensional hydrodynamical simulations of two idealized elliptical galaxies -- one representing a typical galaxy characterized by initial conditions conducive to the development of thermal instability and the other one less likely to develop thermal instability -- in order to study the development of thermal instability and the formation of multi-phase structures. We analyze the interplay between radiative cooling, momentum-driven AGN feedback, star…
There is a well-known discrepancy in the distance estimation for M60, a giant elliptical galaxy in Virgo: the planetary nebula luminosity function (PNLF) distance moduli for this galaxy are, on average, $~0.4$ mag smaller than the values based on the surface brightness fluctuation (SBF) in the literature. We present photometry of the resolved stars in an outer field of M60 based on deep F775W and F850LP images in the Hubble Space Telescope obtained as part of the Pure Parallel Program in the archive. Detected stars are mostly old red giants in the halo of M60. With this photometry we determine…
Based on two-dimensional high resolution hydrodynamic numerical simulation, we study the mechanical and radiative feedback effects from the central AGN on the cosmological evolution of an isolated elliptical galaxy. Physical processes such as star formation and supernovae are considered. The inner boundary of the simulation domain is carefully chosen so that the fiducial Bondi radius is resolved and the accretion rate of the black hole is determined self-consistently. In analogy to previous works, we assume that the specific angular momentum of the galaxy is low. It is well-known that when the…
In this letter we construct a large sample of early-type galaxies with measured gas-phase metallicities from the Sloan Digital Sky Survey and Galaxy Zoo in order to investigate the origin of the gas that fuels their residual star formation. We use this sample to show that star forming elliptical galaxies have a substantially different gas-phase metallicity distribution from spiral galaxies, with ~7.4% having a very low gas-phase metallicity for their mass. These systems typically have fewer metals in the gas phase than they do in their stellar photospheres, which strongly suggests that the mat…
Stellar photometry in nine fields around the giant elliptical galaxy M87 in the Virgo cluster is obtained from archival images of the Hubble Space Telescope. The resulting Hertzsprung--Russell diagrams show populated red-giant and AGB branches. The position of the tip of the red-giant branch (the TRGB discontinuity) is found to vary with galactocentric distance. This variation can be interpreted as the effect of metal-rich red giants on the procedure of the measurement of the TRGB discontinuity or as a consequence of the existence of a weak gas-and-dust cloud around M87 extending out to $10^\p…
We investigated the distribution of resolved asymptotic giant branch (AGB) stars over a much larger area than covered by previous near-infrared studies in the nearby dwarf elliptical galaxy NGC 205. Using data obtained with the WIRCam near-infrared imager of the CFHT, we selected the AGB stars in the JHKs color-magnitude diagrams, and separated the C stars from M-giant stars in the JHKs color-color diagram. We identified 1,550 C stars in NGC 205 with a mean absolute magnitude of M_Ks = -7.49 \pm 0.54, and colors of (J - Ks) = 1.81 \pm 0.41 and (H - Ks) = 0.76 \pm 0.24. The ratio of C stars to …
We have used hydrodynamical simulations to model the formation of the closest giant elliptical galaxy, Centaurus A. We find that a single major merger event with a mass ratio up to 1.5, and which has happened ~2 Gyr ago, is able to reproduce many of its properties, including galaxy kinematics, the inner gas disk, stellar halo ages and metallicities, and numerous faint features observed in the halo. The elongated halo shape is mostly made of progenitor residuals deposited by the merger, which also contribute to stellar shells observed in the Centaurus A halo. The current model also reproduces t…
We have used the ACS and WFC3 cameras on board HST to resolve stars in the halo of the nearest giant elliptical (gE) galaxy NGC 5128 out to a projected distance of 140 kpc (25 effective radii, Reff) along the major axis and 90 kpc (16 Reff) along the minor axis. This dataset provides an unprecedented radial coverage of the stellar halo properties in any gE galaxy. Color-magnitude diagrams clearly reveal the presence of the red giant branch stars belonging to the halo of NGC 5128, even in our most distant fields. The star counts demonstrate increasing flattening of the outer halo, which is elon…
We report the existence of spiral arms in the recently formed gaseous and dusty disk of the closest giant elliptical, NGC 5128 (Centaurus A), using high resolution 12CO(2-1) observations of the central 3 arcmin (3 kpc) obtained with the Submillimeter Array (SMA). This provides evidence that spiral-like features can develop within ellipticals if enough cold gas exists. We elucidate the distribution and kinematics of the molecular gas in this region with a resolution of 4.4 x 1.9 (80 pc x 40 pc). The spiral arms extend from the circumnuclear gas at a radius of 200 pc to at least 1 kiloparsec. Th…
We present a catalog of the 1525 most optically luminous galaxies from the Sloan Digital Sky Survey (SDSS) with r-band luminosity L_r > 8L* and redshift z<0.3, including 84 super spirals, 15 super lenticulars, 14 super post-merger galaxies, and 1400 giant ellipticals. With mass in stars of 10^{11.3}-10^{12} M_sun, super spirals and lenticulars are the most massive disk galaxies currently known. The specific star formation rates of super spirals place them on or below the star-forming main sequence. They must have formed stars at a high rate throughout their history in order to grow their massi…
We present a study of the thermal structure of the hot X-ray emitting atmospheres for a sample of 49 nearby X-ray and optically bright elliptical galaxies using {\it Chandra} X-ray data. We focus on the connection between the properties of the hot X-ray emitting gas and the cooler H$α$+[NII] emitting phase, and the possible role of the latter in the AGN (Active Galactic Nuclei) feedback cycle. We do not find evident correlations between the H$α$+[NII] emission and global properties such as X-ray luminosity, mass of hot gas, and gas mass fraction. We find that the presence of H$α$+[NII] emissio…
Black hole feedback plays a central role in shaping the circumgalactic medium (CGM) of elliptical galaxies. We systematically study the impact of plasma physics on the evolution of ellipticals by performing three-dimensional non-ideal magneto-hydrodynamic simulations of the interactions of active galactic nucleus (AGN) jets with the CGM including magnetic fields, and cosmic rays (CRs) and their transport processes. We find that the physics of feedback operating on large galactic scales depends very sensitively on plasma physics operating on small scales. Specifically, we demonstrate that: (i) …
Recent observational results provide possible evidence that binary black holes (BBHs) exist in the center of giant galaxies and may merge to form a supermassive black hole in the process of their evolution. We first detected a periodic flux variation on a cycle of $93\pm1$ days from the 3-mm monitor observations of a giant elliptical galaxy \object{3C 66B} for which an orbital motion with a period of $1.05\pm0.03$ years had been already observed. The detected signal period being shorter than the orbital period can be explained by taking into consideration the Doppler-shifted modulation due to …
We present ALMA CO(1-0) observations toward the dust lane of the nearest elliptical and radio galaxy, NGC 5128 (Centaurus A), with high angular resolution ($\sim$ 1 arcsec, or 18 pc), including information from large to small spatial scales and total flux. We find a total molecular gas mass of 1.6$\times$10$^9$ $M_\odot$ and we reveal the presence of filamentary components more extended than previously seen, up to a radius of 4 kpc. We find that the global star formation rate is $\sim$1 \Msol yr$^{-1}$, which yields a star formation efficiency (SFE) of 0.6 Gyr$^{-1}$ (depletion time $τ=$1.5 Gy…
We present the first census of giant molecular clouds (GMCs) complete down to 10$^6 M_{\odot}$ and within the inner 4 kpc of the nearest giant elliptical and powerful radio galaxy, Centaurus A. We identified 689 GMCs using CO(1--0) data with 1" spatial resolution ($\sim 20$ pc) and 2 km/s velocity resolution obtained with the Atacama Large Millimeter/submillimeter Array (ALMA). The $I$(CO)-$N$(H$_2$) conversion factor based on the virial method is $X_{\rm CO}$ = $(2 \pm 1 )\times10^{20}$ cm$^{-2}$(K km/s)$^{-1}$ for the entire molecular disk, consistent with that of the disks of spiral galaxie…
Observations of diffuse starlight in the outskirts of galaxies are thought to be a fundamental source of constraints on the cosmological context of galaxy assembly in the $Λ$CDM model. Such observations are not trivial because of the extreme faintness of such regions. In this work, we investigate the photometric properties of six massive early type galaxies (ETGs) in the VEGAS sample (NGC 1399, NGC 3923, NGC 4365, NGC 4472, NGC 5044, and NGC 5846) out to extremely low surface brightness levels, with the goal of characterizing the global structure of their light profiles for comparison to state…
We present virial models for the global evolution of giant molecular clouds. Focusing on the presence of an accretion flow, and accounting for the amount of mass, momentum, and energy supplied by accretion and star formation feedback, we are able to follow the growth, evolution, and dispersal of individual giant molecular clouds. Our model clouds reproduce the scaling relations observed in both galactic and extragalactic clouds. We find that accretion and star formation contribute contribute roughly equal amounts of turbulent kinetic energy over the lifetime of the cloud. Clouds attain virial …
The importance of feedback (radiative and mechanical) from massive black holes at the centers of elliptical galaxies is not in doubt, given the well established relation among black hole mass and galaxy optical luminosity. Here, with the aid of high-resolution hydrodynamical simulations, we discuss how this feedback affects the hot ISM of isolated elliptical galaxies of different mass. The cooling and heating functions include photoionization plus Compton heating, the radiative transport equations are solved, and the mechanical feedback due to the nuclear wind is also described on a physical b…
Several recent studies have provided evidence for a `bottom-heavy' stellar initial mass function (IMF) in massive elliptical galaxies. Here we investigate the influence of the IMF shape on the recently discovered color-magnitude relation (CMR) among globular clusters (GCs) in such galaxies. To this end we use calculations of GC mass loss due to stellar and dynamical evolution to evaluate (i) the shapes of stellar mass functions in GCs after 12 Gyr of evolution as a function of current GC mass along with their effects on integrated-light colors and mass-to-light ratios, and (ii) their impact on…
Context. Stellar shells, which form axially symmetric systems of arcs in some elliptical galaxies, are most likely remnants of radial minor mergers. They are observed up a radius of $\sim$100 kpc. The stars in them oscillate in radial orbits. The radius of a shell depends on the free-fall time at the position of the shell and on the time since the merger. We previously verified the consistency of shell radii in the elliptical galaxy NGC 3923 with its most probable MOND potential. Our results implied that an as~yet undiscovered shell exists at the outskirts of the galaxy. Aims. We here extend o…
We construct a suite of discrete chemo-dynamical models of the giant elliptical galaxy NGC 5846. These models are a powerful tool to constrain both the mass distribution and internal dynamics of multiple tracer populations. We use Jeans models to simultaneously fit stellar kinematics within the effective radius $R_{\rm e}$, planetary nebula (PN) radial velocities out to $3\, R_{\rm e}$, and globular cluster (GC) radial velocities and colours out to $6\,R_{\rm e}$. The best-fitting model is a cored DM halo which contributes $\sim 10\%$ of the total mass within $1\,R_{\rm e}$, and $67\% \pm 10\%…
Globular clusters (GC) are important objects for tracing the early evolution of a galaxy. We study the relation between the properties of globular cluster systems - as quantified by the GC specific frequency (SN) - and the properties of their host galaxies. In order to understand the origin of the relation between the GC specific frequency (SN) and galaxy mass, we devise a theoretical model for the specific frequency (SN,th). GC erosion is considered to be an important aspect for shaping this relation, since observations show that galaxies with low densities have a higher SN, while high densit…
We report a systematic and statistically significant offset between the optical (g-z or B-I) colors of seven massive elliptical galaxies and the mean colors of their associated massive metal-rich globular clusters (GCs) in the sense that the parent galaxies are redder by 0.12-0.20 mag at a given galactocentric distance. However, spectroscopic indices in the blue indicate that the luminosity-weighted ages and metallicities of such galaxies are equal to that of their averaged massive metal-rich GCs at a given galactocentric distance, to within small uncertainties. The observed color differences …
We study the radio emission of the most massive galaxies in a sample of dynamically relaxed and un-relaxed galaxy groups from Galaxy and Mass Assembly (GAMA). The dynamical state of the group is defined by the stellar dominance of the brightest group galaxy, e.g. the luminosity gap between the two most luminous members, and the offset between the position of the brightest group galaxy and the luminosity centroid of the group. We find that the radio luminosity of the most massive galaxy in the group strongly depends on its environment, such that the brightest group galaxies in dynamically young…
Stellar metallicity distribution functions (MDF) have been measured for resolved stellar populations in the outer halos of many galaxies in nearby groups. Among them, the MDF of NGC 5128, the central giant elliptical in the Centaurus group, provides essential constraints for theories of massive galaxy formation and hierarchical assembly. To investigate the formation and chemical evolution history of the outer halo of giant elliptical galaxies, we examine the chemical properties of three zoom-in high resolution cosmological hydrodynamical simulations of an NGC 5128-like giant elliptical galaxy …
We present new VLT observations of the closest-known strong-lensing galaxy, the sigma=330 km/s giant elliptical ESO325-G004. The low redshift of the lens (z_lens=0.035) results in arcs being formed at a small fraction of the effective radius, (R_Ein ~ R_Eff/4). At such small radii, stars dominate the lensing mass, so that lensing provides a direct probe of the stellar mass-to-light ratio, with only small corrections needed for dark matter. The redshift of the galaxy lensed by ESO325-G004 was unknown until now, so the lensing mass was not securely determined. Using X-SHOOTER, we measure a secur…
We present archival Spitzer photometry and spectroscopy, and Herschel photometry, of the peculiar "Green Valley" elliptical galaxy NGC~3226. The galaxy, which contains a low-luminosity AGN, forms a pair with NGC~3227, and is shown to lie in a complex web of stellar and HI filaments. Imaging at 8 and 16$μ$m reveals a curved plume structure 3 kpc in extent, embedded within the core of the galaxy, and coincident with the termination of a 30 kpc-long HI tail. In-situ star formation associated with the IR plume is identified from narrow-band HST imaging. The end of the IR-plume coincides with a war…
We study the mass and anisotropy distribution of the giant elliptical galaxy NGC 5846 using stars, as well as the red and blue globular cluster (GC) subpopulations. We break degeneracies in the dynamical models by taking advantage of the different phase space distributions of the two GC subpopulations to unambiguously constrain the mass of the galaxy and the anisotropy of the GC system. Red GCs show the same spatial distribution and behaviour as the starlight, whereas blue GCs have a shallower density profile, a larger velocity dispersion and a lower kurtosis, all of which suggest a different …
The isolated elliptical (IE) NGC 7796 is accompanied by an interesting early-type dwarf galaxy, named NGC7796-DW1. It exhibits a tidal tail, very boxy isophotes, and multiple nuclei or regions (A, B, and C) that are bluer than the bulk population of the galaxy, indicating a younger age. These properties are suggestive of a dwarf-dwarf merger remnant. We use the Multi-Unit Spectroscopic Explorer (MUSE) at the VLT to investigate NGC 7796-DW1. We extract characteristic spectra to which we apply the STARLIGHT population synthesis software to obtain ages and metallicities of the various population …
We discuss the effects of destruction of wide binaries in the nuclei of the lower mass giant elliptical galaxies. We show that the numbers of barium stars and extrinsic S stars should be dramatically reduced in these galaxies compared to what is seen in the largest elliptical galaxies. Given that the extrinsic S stars show strong Wing-Ford band and Na I D absorption, we argue that the recent claims of different initial mass functions from the most massive elliptical galaxies versus lower mass ellipticals may be the result of extrinsic S stars, rather than bottom-heavy initial mass function.
It is demonstrated that the Local Sheet is both geometrically and dynamically distinct from the Local Supercluster and that the evolution of the Sheet and Local Group were probably interconnected. The Sheet is inclined by 8 degrees with respect to the Local Supercluster, and the dispersion of giant members about the mid-plane is only 230 kpc. A "Council of Giants" with a radius of 3.75 Mpc encompasses the Local Group, demarcating a clear upper limit to the realm of influence of the Local Group. The only two giant elliptical galaxies in the Sheet sit on opposite sides of the Council, raising th…
The recently discovered apparent dramatic expansion in the effective radii of massive elliptical galaxies from $z \simeq 2$ to $z \simeq 0.1$ has been interpreted in terms of either galaxy mergers or the rapid loss of cold gas due to AGN feedback. In examining the latter case we have quantified the extent of the expansion, which is uncertain observationally, in terms of the star formation parameters and time of the expulsion of the cold gas. In either case, the large global decrease in stellar density should translate into a major drop in the ISM density and pressure, and a much steeper radial…
