Luminosity Function Constraints on the Evolution of Massive Red Galaxies Since z~0.9
Richard J. Cool, Daniel J. Eisenstein, Xiaohui Fan, Masataka Fukugita, Linhua Jiang, Claudia Maraston, Avery Meiksin, Donald P. Schneider, David A. Wake
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19 pages, 19 figures, 7 tables; accepted for publication in ApJ
We measure the evolution of the luminous red galaxy (LRG) luminosity function in the redshift range 0.1<z<0.9 using samples of galaxies from the Sloan Digital Sky Survey as well as new spectroscopy of high-redshift massive red galaxies. Our high-redshift sample of galaxies is largest spectroscopic sample of massive red galaxies at z~0.9 collected to date and covers 7 square deg, minimizing the impact of large scale structure on our results. We find that the LRG population has evolved little beyond the passive fading of its stellar populations since z~0.9. Based on our luminosity function measurements and assuming a non-evolving Salpeter stellar initial mass function, we find that the most massive (L>3L*) red galaxies have grown by less than 50% (at 99% confidence), since z=0.9, in stark contrast to the factor of 2-4 growth observed in the L* red galaxy population over the same epoch. We also investigate the evolution of the average LRG spectrum since z~0.9 and find the high-redshift composite to be well-described as a passively evolving example of the composite galaxy observed at low-redshift. From spectral fits to the composite spectra, we find at most 5% of the stellar mass in massive red galaxies may have formed within 1Gyr of z=0.9. While L* red galaxies are clearly assembled at z<1, 3L* galaxies appear to be largely in place and evolve little beyond the passive evolution of their stellar populations over the last half of cosmic history.
We construct a physically motivated analytical model for the quasar luminosity function, based on the joint star formation and feeding of massive black holes suggested by the observed correlation between the black hole mass and the stellar mass of the hosting spheroids. The parallel growth of massive black holes and host galaxies is assumed to be triggered by major mergers of haloes. The halo major merger rate is computed in the frame of the extended Press-Schechter model. The evolution of black holes on cosmological timescales is achieved by the integration of the governing set of differentia…
We compare pure luminosity evolution (PLE) models with recent data at low and high redshift. These models assume that massive galaxies were assembled and formed most of their stars at high redshift (z > 3) and have evolved without merging or substantial dust obscuration since then. Our models span the full range of plausible metallicities, initial mass functions (IMF's) and star formation histories. We require them to reproduce the abundance of galaxies by colour and luminosity in the Sloan Digital Sky Survey and we investigate whether they can simultaneously fit (i) the observed galaxy counts…
We derive radial profiles of the surface-mass-density for 19 spiral galaxies directly from their high-resolution rotation curves. Using the corresponding luminosity profiles, we obtain the radial distribution of the mass-to-luminosity ratios ($M/L$) from the inner bulge ($\sim$ a few 100 pc) to the outer disk ($\geq$ 2-10 kpc) for 11 galaxies (with inclination < $70^{\circ}$ in order to reduce the influence of the interstellar extinction. The $M/L$s in the bulges of two galaxies with sufficient resolution, NGC 4527 and NGC 6946, are found to increase steeply toward the center at radii $\sim$ 1…
We investigate a large number of cosmological evolution models for QSOs and Active Galactic Nuclei (AGN). We introduce a spectrum-luminosity correlation as a new input parameter and adopt the estimated mass function (MF) of massive black holes in centers of nearby galactic nuclei as a constraint to distinguish among different QSO/AGN models. We explore three basic types of phenomenological scenarios; (i) Models with multiple short-lived ($\sim$ a few $10^{6-8}$ yrs) populations, (ii) Models with a single long-lived ($\sim 10^9$ yr) QSO population, and (iii) Models with recurrent QSO/AGN activi…
K band observations of the galaxy populations of three high redshift (z=0.8-1.0), X-ray selected, massive clusters are presented. The observations reach a depth of K=21.5, corresponding to K*+3.5 mag. The evolution of the galaxy properties are discussed in terms of their K band luminosity functions and the K band Hubble diagram of brightest cluster galaxies. The bulk of the galaxy luminosities, as characterised by the parameter K* from the Schechter (1976) function, are found to be consistent with passive evolution with a redshift of formation of z_f~1.5-2. This is consistent with observations…
We measure the rest-frame B-band luminosity function of red-sequence galaxies (RSLF) of five intermediate-redshift (0.5 < z < 0.9), high-mass (sigma > 950 km/s) clusters. Cluster galaxies are identified through photometric redshifts based on imaging in seven bands (five broad, and two narrow) using the WIYN 3.5m telescope. The luminosity functions are well-fit down to M_B^*+3 for all of the clusters out to a radius of R_200. For comparison, the luminosity functions for a sample of 59 low redshift clusters selected from the SDSS are measured as well. There is a brightening trend (M_B^* increase…
Growth of massive black holes (MBHs) in galactic centers comes mainly from gas accretion during their QSO/AGN phases. In this paper we apply an extended Soltan argument, connecting the local MBH mass function with the time-integral of the QSO luminosity function, to the demography of MBHs and QSOs from recent optical and X-ray surveys, and obtain robust constraints on the luminosity evolution (or mass growth history) of individual QSOs (or MBHs). We find that the luminosity evolution probably involves two phases: an initial exponentially increasing phase set by the Eddington limit and a follow…
High-resolution nuclear-to-outer rotation curves for Sb, SBb, Sc, and SBc galaxies show generally a steep nuclear rise and flat rotation from the disk to halo. The high-velocity central rotation indicates massive core within bulges. Since this characteristics is common to most galaxies, the high-velocity central rotation cannot be due to a particular orientation of non-circular motion. Using these rotation curves, we derive the distributions of surface-mass density, and compare directly with observed surface-luminosity distributions. The mass-to-luminosity ratio (M/L) remains constant in the o…
An empirically motivated model is presented for accretion-dominated growth of the super massive black holes (SMBH) in galaxies, and the implications are studied for the evolution of the quasar population in the universe. We investigate the core aspects of the quasar population, including space density evolution, evolution of the characteristic luminosity, plausible minimum masses of quasars, the mass function of SMBH and their formation epoch distribution. Our model suggests that the characteristic luminosity in the quasar luminosity function arises primarily as a consequence of a characterist…
A number of supernovae, classified as Type II, show remarkably peculiar properties such as an extremely low expansion velocity and an extraordinarily small amount of $^{56}$Ni in the ejecta. We present a joint analysis of the available observations for two of these peculiar Type II supernovae, SN 1997D and SN 1999br, using a comprehensive semi-analytic method that can reproduce the light curve and the evolution of the line velocity and continuum temperature. We find that these events are under-energetic with respect to a typical Type II supernova and that the inferred mass of the ejecta is rel…
In the local universe, the masses of Super-Massive Black-Holes (SMBH) appear to correlate with the physical properties of their hosts, including the mass of the dark-matter halo. Using these clues as a starting point many studies have produced models that can explain phenomena like the quasar luminosity function. The shortcoming of this approach is that working models are not unique, and as a result it is not always clear what input physics is being constrained. Here we take a different approach. We identify critical parameters that describe the evolution of SMBHs at high redshift, and constra…
Young massive clusters (YMCs) differ markedly from old globular clusters in featuring extended, rather than tidally truncated, envelopes. Their projected- luminosity profiles are well fit by Elson-Fall-Freeman (EFF) models with core radii of 0.3 pc < r_c < 8 pc and power-law envelopes of negative exponent 2 < gamma < 3.8. These envelopes form within the first few 10^6 yr and last ~10^8 to 10^9.5 yr, depending on the environment. Many young massive clusters show clumpy substructure that may accelerate their initial relaxation. The cores of Magellanic-Cloud clusters show universal expansion from…
The population of newly formed massive stars, while still embedded in their parent molecular clouds, is studied on the galactic disk scale. We analyse the luminosity function of IRAS point-like sources, with far-infrared (FIR) colours of ultra-compact HII regions, that have been detected in the CS(2-1) line - a tracer of high density molecular gas. The FIR luminosities of 555 massive star forming regions (MSFRs), 413 of which lie within the solar circle, are inferred from their fluxes in the four IRAS bands and from their kinematic distances, derived using the CS(2-1) velocity profiles. The lu…
We study the relationship between galaxy luminosity, color, and environment in a cosmological simulation of galaxy formation. We compare the predicted relationship with that found for SDSS galaxies and find that the model successfully predicts most of the qualitative features seen in the data, but also shows some interesting differences. Specifically, the simulation predicts that the local density around bright red galaxies is a strong increasing function of luminosity, but does not depend much on color at fixed luminosity. Moreover, we show that this is due to central galaxies in dark matter …
We report a serendipitous discovery of six very low-luminosity active galactic nuclei (AGNs) only by optical variability in one-month baseline. The detected flux variability is ~ 1-5% of the total luminosity of host galaxies. Careful subtraction of host galaxy components in nuclear regions indicates that the fractional variability (Delta F / F) of the nuclei is of order unity. At least one of them is showing a compelling flaring activity within just a few days, which appears to be quite different from previously known AGN variability. We obtained spectroscopic data for the one showing the larg…
The problem of the formation and evolution of field massive galaxies is briefly reviewed from an observational perspective. The motivations and the characteristics of the K20 survey are outlined. The redshift distribution of Ks<20 galaxies, the evolution of the rest-frame Ks-band luminosity function and luminosity density to z=1.5, the nature and the role of the red galaxy population are presented. Such results are compared with the predictions of models of galaxy evolution.
We present the results of spectral energy distribution analysis for 162 of the 405 sources reported in the SIMBA survey of Hill et al. (2005). The fits reveal source specific parameters including: the luminosity, mass, temperature, H$_2$ number density, the surface density and the luminosity-to-mass ratio. Each of these parameters are examined with respect to the four classes of source present in the sample. Obvious luminosity and temperature distinctions exist between the mm-only cores and those cores with methanol maser and/or radio continuum emission, with the former cooler and less luminou…
The empirically determined universal power-law shape of X-ray luminosity function of high mass X-ray binaries in galaxies is explained by fundamental mass-luminosity and mass-radius relations for massive stars.
Massive black holes detected in the centers of many nearby galaxies are linearly correlated with the luminosity of the host bulge, the black hole mass being about 0.1% of the bulge mass. An even stronger relation exists between the BH mass (Mbh) and the stellar velocity dispersion in the host bulge. We show that massive BHs of AGNs (measured by reverberation mapping) and their bulge luminosity (measured by using a bulge/disk decomposition) follow the same relations as ordinary (inactive) galaxies, with the exeption of narrow line AGN which apparently have significantly lower BH/bulge ratios. N…
With a redshift of z=5.5 and an optical blue magnitude M_B ~ -24.2 mag (~4.5 10^12 L_sun), RDJ030117+002025 is the most distant optically faint (M_B > -26 mag) quasar known. MAMBO continuum observations at lambda=1.2 mm (185 micrometer rest-frame) showed that this quasar has a far-IR luminosity comparable to its optical luminosity. We present near-infrared J- and K-band photometry obtained with NIRC on the Keck I telescope, tracing the slope of the rest frame UV spectrum of this quasar. The observed spectral index is close to the value of alpha_nu ~ -0.44 measured in composite spectra of optic…
We present a new analysis of the rest-frame B-band COMBO-17 and DEEP2 luminosity functions (LFs) of early-type galaxies (ETGs) as a function of luminosity and mass. Our aim is to place new stringent constraints on the evolution of ETGs since z~1. We correct the LF($z$) data for the luminosity dimming assuming pure luminosity evolution. However, instead of relying on stellar population synthesis model--dependent assumptions, we adopt the empirical luminosity dimming rate derived from the evolution of the Fundamental Plane of field and cluster massive ETGs.Our results show that the amount of evo…
We derive the rest-frame $K$-band luminosity function for galaxies in 32 clusters at $0.6 < z < 1.3$ using deep $3.6μ$m and $4.5μ$m imaging from the Spitzer Space Telescope InfraRed Array Camera (IRAC). The luminosity functions approximate the stellar mass function of the cluster galaxies. Their dependence on redshift indicates that massive cluster galaxies (to the characteristic luminosity $M^*_K$) are fully assembled at least at $z \sim 1.3$ and that little significant accretion takes place at later times. The existence of massive, highly evolved galaxies at these epochs is likely to represe…
(abridged) The Carina Nebula (NGC 3372) is our richest nearby laboratory in which to study feedback through UV radiation and stellar winds from very massive stars during the formation of an OB association before supernova explosions have influenced the environment. This paper takes inventory of the combined effect from all the known massive stars that power the Carina Nebula. The present-day total ionizing photon luminosity produced by the 65 O stars and 3 WNL stars in Carina is about 1e51/s, the total bolometric luminosity of all stars earlier than B2 is 2.5e7 Lsun, and the total mechanical l…
HST UV STIS imaging and spectroscopy of the low luminosity AGN (LLAGN) NGC 4303 have identified the previously detected UV-bright nucleus of this galaxy, as a compact, massive and luminous stellar cluster. The cluster with a size (FWHM) of 3.1 pc, and an ultraviolet luminosity log L (1500 A}(erg/s/A)= 38.33 is identified as a nuclear super star cluster (SSC) like those detected in the circumnuclear regions of spirals and starburst galaxies. The UV spectrum showing the characteristic broad P Cygni lines produced by the winds of massive young stars, is best fitted by the spectral energy distribu…
We present evidence of the co-existence of either an AGN or an ultraluminous X-ray source (ULX), together with a young super stellar cluster in the 3 central parsecs of NGC4303. The galaxy contains a low luminosity AGN and hosts a number of starburst regions in a circumnuclear spiral, as well as in the nucleus itself. A high spatial resolution Chandra image of this source reveals that the soft X-ray emission traces the ultraviolet nuclear spiral down to a core, which is unresolved both in soft and hard X-rays. The astrometry of the X-ray core coincides with the UV core within the Chandra posit…
We propose that there exists a class of transient sources, "squeezars", which are stars caught in highly eccentric orbits around a massive (m<10^8 Mo) black hole (MBH), whose atypically high luminosity (up to a significant fraction of their Eddington luminosity) is powered by tidal interactions with the MBH. Their existence follows from the presence of a mass sink, the MBH, in the galactic center, which drives a flow of stars into nearly radial orbits to replace those it has destroyed. We consider two limits for the stellar response to tidal heating: surface heating with radiative cooling ("ho…
K band luminosity functions (LFs) of three, massive, high redshift clusters of galaxies are presented. The evolution of K*, the characteristic magnitude of the LF, is consistent with purely passive evolution, and a redshift of forma tion z = 1.5-2.
Using Hubble Space Telescope observations with STIS, we study the main exciting stars of N81, a high excitation compact Hii region in the Small Magellanic Cloud (SMC). These far UV observations are the first spectroscopic measurements of stars in such a region and reveal features characteristic of an O6-O8 stellar type. The astonishing weakness of their wind profiles and their sub-luminosity (up to ~ 2 mag fainter in Mv than the corresponding dwarfs) make these stars a unique stellar population in the Magellanic Clouds. Our analysis suggests that they are probably in the Hertzsprung-Russell di…
We present the azimuthally averaged radial distribution of 748 regions of OB star formation in the whole galactic disk, based on our previous CS(2-1) survey of UC H II regions. Embedded massive stars produce a total FIR luminosity of 1.39E8 Lsun within the range 0.2<R/Ro<2 in galactocentric radius. We find 492 massive star forming regions within the solar circle, producing 81% of the total FIR luminosity. Separate analyses of the 349 sources in the I and II quadrant (north), and of the 399 sources in the III and IV quadrant (south), yield FIR luminosities (extrapolated to the complete galactic…
We present the first results of a spectroscopic study of young massive stars in the SMC High Excitation Blob N81. These stars have Mv values which are ~ 2 mag smaller than those of nor mal dwarf stars. Their UV STIS spectra reveal features typical of O stars, but surprisingly weak wind components. The preliminary modelling of these spectr a with the code CMFGEN (Hillier & Miller 1998) indicates a mass loss rate of the order 10e-9 Mdot/yr. If confirmed, such a weak wind may indicate either a breakdown of the wind-momentum luminosity relation at low luminosity, or a steeper slope of this relatio…
We explored the clustering properties of Lyman Break Galaxies (LBGs) at z=4 and 5 with an angular two-point correlation function on the basis of the very deep and wide Subaru Deep Field data. We found an apparent dependence of the correlation function slope on UV luminosity for LBGs at both z=4 and 5. More luminous LBGs have a steeper correlation function. To compare these observational results, we constructed numerical mock LBG catalogs based on a semianalytic model of hierarchical clustering combined with high-resolution N-body simulation, carefully mimicking the observational selection effe…
I will discuss the presence of massive star clusters in starburst galaxies with an emphasis on low mass galaxies outside the local group. I will show that such galaxies, with respect to their mass and luminosity, may be very rich in young luminous clusters.
We investigate how hierarchical models for the co-evolution of the massive black hole (MBH) and AGN population can reproduce the observed faint X-ray counts. We find that the main variable influencing the theoretical predictions is the Eddington ratio of accreting sources. We compare three different models proposed for the evolution of AGN Eddington ratio, f_Edd: constant f_Edd=1, f_Edd decreasing with redshift, and f_Edd depending on the AGN luminosity, as suggested by simulations of galactic mergers including BHs and AGN feedback. We follow the full assembly of MBHs and host halos from early…
We present an XMM-Newton observation of the massive edge-on Sb galaxy NGC 2613. We discover that this galaxy contains a deeply embedded active nucleus with a 0.3-10 keV luminosity of 3.3x10^40 erg/s and a line-of-sight absorption column of 1.2x10^23 cm^-2. Within the 25 mag/arcsec^2 optical B-band isophote of the galaxy, we detect an additional 4 sources with an accumulated luminosity of 4.3x10^39 erg/s. The bulk of the unresolved X-ray emission spatially follows the near-infrared (NIR) K-band surface brightness distribution; the luminosity ratio L_X/L_K ~ 8x10^-4 is consistent with that infer…
We identify a large sample of isolated bright galaxies and their fainter satellites in the 2dF Galaxy Redshift Survey (2dFGRS). We analyse the dynamics of ensembles of these galaxies selected according to luminosity and morphological type by stacking the positions of their satellites and estimating the velocity dispersion of the combined set. We test our methodology using realistic mock catalogues constructed from cosmological simulations. The method returns an unbiased estimate of the velocity dispersion provided that the isolation criterion is strict enough to avoid contamination and that th…
Populations of young star clusters show significant differences even among "normal" disk galaxies. In this contribution I discuss how properties of young cluster systems are related to those of their host galaxies, based on a recent study of clusters in a sample of 22 nearby spiral galaxies. Luminous young clusters similar to the "super" star clusters observed in starbursts and mergers exist in several of these galaxies, and it is found that the luminosity of the brightest star cluster as well as the specific luminosity of the cluster systems both correlate well with the host galaxy star forma…
A search for young massive star clusters (YMCs) in the nearby face-on spiral galaxy M51 (NGC 5194) has been carried out using UBV CCD images from the prime focus camera on the Lick 3 meter Shane telescope. The YMC population is found to be quite rich with a specific U-band luminosity T_L(U) = 1.4, consistent with the high current star formation rate of this galaxy. The brightest clusters have M_V about -12.5, far brighter than any young clusters currently known in the Milky Way and even surpassing the luminosity of the R136 cluster in the 30 Dor complex in the Large Magellanic Cloud. A few of …
To address the problem concerning the early formation of stars in massive galaxies, we present the results of a semi-analytic model of galaxy formation which includes a physical description of starbursts triggered by galaxy interactions. These originate from the destabilization of cold galactic gas occurring in galaxy encounters, which in part feeds the accretion onto black holes powering quasars, and in part drives circumnuclear starsbursts at redshifts $z\approx 2-4$, preferentially in massive objects. This speeds up the formation of stars in massive galaxies at high redshifts without alteri…
We present results from JHKs imaging of the densest region of the W49 molecular cloud. In a recent paper (Alves & Homeier 2003), we reported the detection of (previously unknown) massive stellar clusters in the well-known giant radio HII region W49A, and here we continue our analysis. We use the extensive line-of-sight extinction to isolate a population of objects associated with W49A. We constrain the slope of the stellar luminosity function by constructing an extinction-limited luminosity function, and use this to obtain a mass function. We find no evidence for a top-heavy MF, and the slope …
Optically-thick envelopes may form following the tidal disruption of a star by a massive black hole. Such envelopes would reprocess hard radiation from accretion close to the black hole into the UV and optical bands producing AGN-luminosity flares with duration ~1 year. We show that due to relativistic effects, the envelopes are convective. If convection is efficient, then the structure of the envelopes is similar to that described in previous work; however, the photospheric radius is shown to be very sensitive to the luminosity at the envelope base, suggesting that either the envelope collaps…
We use a statistical sample of ~500 rich clusters taken from 72 square degrees of the Red-Sequence Cluster Survey (RCS-1) to study the evolution of ~30,000 red-sequence galaxies in clusters over the redshift range 0.35<z<0.95. We construct red-sequence luminosity functions (RSLFs) for a well-defined, homogeneously selected, richness limited sample. The RSLF at higher redshifts shows a deficit of faint red galaxies (to M_V=> -19.7) with their numbers increasing towards the present epoch. This is consistent with the `down-sizing` picture in which star-formation ended at earlier times for the mos…
We present the results of a comprehensive Spitzer survey of 69 radio galaxies across 1<z<5.2. Using IRAC (3.6-8.0um), IRS (16um) and MIPS (24-160um) imaging, we decompose the rest-frame optical to infrared spectral energy distributions into stellar, AGN, and dust components and determine the contribution of host galaxy stellar emission at rest-frame H-band. Stellar masses derived from rest-frame near-IR data, where AGN and young star contributions are minimized, are significantly more reliable than those derived from rest-frame optical and UV data. We find that the fraction of emitted light at…
Photometric redshifts have been determined for the galaxies in the Hubble Deep Field. The resulting redshift distribution shows two peaks: one at z~0.6 and one at z~2.2. Luminosity functions derived from the redshifts show strong luminosity evolution as a function of redshift. This evolution is consistent with the Babul & Rees (1992) scenario wherein massive galaxies form stars at high redshift while star formation in dwarf galaxies is delayed until after z=1.
Context. Statistical properties of HII region populations in disk galaxies yield important clues to the physics of massive star formation. Aims. We present a set of HII region catalogues and luminosity functions for a sample of 56 spiral galaxies in order to derive the most general form of their luminosity function. Methods. HII region luminosity functions are derived for individual galaxies which, after photometric calibration, are summed to form a total luminosity function comprising 17,797 HII regions from 53 galaxies. Results. The total luminosity function, above its lower limit of complet…
The luminosity dependence of kinematical and isophotal properties of elliptical galaxies is investigated using numerical simulations of galaxy merging, combined with semi-analytical models of hierarchical structure formation. Mergers of spiral galaxies as the only formation mechanism for elliptical galaxies can neither reproduce the kinematical and photometric properties of very massive elliptical galaxies nor the change from rotationally flattened disky to anisotropic boxy systems with increasing luminosity. We present numerical simulations showing that binary mergers of early-type galaxies o…
We have observed the ultracompact HII region G29.96-0.02 in the near infrared J, H, and K bands and in the Br-gamma line. By comparison with radio observations, we determine that the extinction to the nebula is AK = 2.14 with a 3 sigma uncertainty of 0.25. We identify the ionizing star and determine its intrinsic K magnitude. The star does not have an infrared excess and so appears to be no longer accreting. The K magnitude and the bolometric luminosity allow us to place limits on the location of the ionizing star in the HR diagram. The 3 sigma upper limit on the effective temperature of the i…
Results are presented of a survey of SiO 5-4 emission observed with the James Clerk Maxwell Telescope (JCMT) towards a sample of outflows from massive young stellar objects. The sample is drawn from a single-distance study by Ridge & Moore. In a sample of 12 sources, the 5-4 line was detected in 5, a detection rate of 42 per cent. This detection rate is higher than that found for a sample of low-luminosity outflow sources, although for sources of comparable luminosity, it is in good agreement with the results of a previous survey of high luminosity sources. For most of the detected sources, th…
We use a simple model of spheroid formation to explore the relationship between the creation of stars and dust in a massive proto galaxy and the growth of its central black hole. This model predicts that sub-mm luminosity peaks after only ~ 0.2 Gyr. However, without a very massive seed black hole, Eddington-limited growth means that a black hole mass of 10^9 solar masses, and hence very luminous AGN activity, cannot be produced until > 0.5 Gyr after the formation of the first massive stars in the halo. The model thus predicts a time-lag between the peak of sub-mm luminosity and AGN luminosity …
We present near-infrared imaging of the host galaxies of 17 quasars in the redshift range 1 < z < 2, carried out at the ESO VLT UT1 8m telescope under excellent seeing conditions (~0.4 arcsec). The sample includes radio-loud (RLQ) and radio-quiet (RQQ) quasars with similar distribution of redshift and optical luminosity. For all the observed objects but one we have derived the global properties of the surrounding nebulosity. The host galaxies of both types of quasars follow the expected trend in luminosity of massive ellipticals undergoing simple passive evolution, but there is a systematic di…
There are two major approaches to modelling galaxy evolution. The traditional view is that the most massive galaxies were assembled early and have evolved with steeply declining star formation rates since a redshift of 2 or higher. According to hierarchical theories, massive galaxies were assembled much more recently from mergers of smaller subunits. Here we present a simple observational test designed to differentiate between the two. The observed K-band flux from a galaxy is a good measure of its stellar mass even at high redshift. It is probably only weakly affected by dust extinction. We c…
Observations have shown that the Eddington ratios (the ratio of the bolometric luminosity to the Eddington luminosity) in QSOs/active galactic nuclei (AGNs) cover a wide range. In this paper we connect the demography of AGNs obtained by the Sloan Digital Sky Survey with the accretion physics around massive black holes and propose that the diversity in the Eddington ratios is a natural result of the long-term evolution of accretion disks in AGNs. The observed accretion rate distribution of AGNs (with host galaxy velocity dispersion sigma~70-200 km/s) in the nearby universe (z<0.3) is consistent…
Using spectroscopic data from the Deep Extragalactic Evolutionary Probe (DEEP) Groth Strip survey (DGSS), we analyze the gas-phase oxygen abundances in the warm ionized medium for 64 emission-line field galaxies in the redshift range 0.26<z<0.82. Oxygen abundances relative to hydrogen range between 8.4<12+log(O/H)<9.0 with typical internal plus systematic measurement uncertainties of 0.17 dex. The 64 DGSS galaxies collectively exhibit an increase in metallicity with B-band luminosity. DGSS galaxies in the highest redshift bin (z=0.6-0.82) are brighter, on average, by ~1 mag at fixed metallicit…
We have determined the location of the line-opacity modified Eddington limit for stars in the LMC using the most recent atmosphere models combined with a precise mapping to the HR Diagram through up-to-date stellar evolution calculations. While we find, in agreement with previous studies, that the shape of the modified Eddington limit qualitatively corresponds to the Humphreys-Davidson (HD) limit defined by the most luminous supergiants, the modified limit is actually a full magnitude higher than the upper luminosity limit observed for LMC stars. The observed limit is consistent with atmospher…
We present near-infrared imaging with ESO VLT+ISAAC of the host galaxies of low luminosity quasars in the redshift range 1 < z < 2, aimed at investigating the relationship between the nuclear and host galaxy luminosities at high redshift. This work complements our previous study to trace the cosmological evolution of the host galaxies of high luminosity quasars (Falomo et al. 2004). The new sample includes 15 low luminosity quasars, nine radio-loud (RLQ) and six radio-quiet (RQQ). They have similar distribution of redshift and optical luminosity, and together with the high luminosity quasars t…
The importance of the radiative feedback from massive black holes at the centers of elliptical galaxies is not in doubt, given the well established relations among electromagnetic output, black hole mass and galaxy optical luminosity. We show how this AGN radiative output affects the hot ISM of an isolated elliptical galaxy with the aid of a high-resolution hydrodynamical code, where the cooling and heating functions include photoionization plus Compton heating. We find that radiative heating is a key factor in the self-regulated coevolution of massive black holes and their host galaxies and t…
We calculate the probability to form giant radio halos (~ 1 Mpc size) as a function of the mass of the host clusters by using a Statistical Magneto-Turbulent Model (Cassano & Brunetti, these proceedings). We show that the expectations of this model are in good agreement with the observations for viable values of the parameters. In particular, the abrupt increase of the probability to find radio halos in the more massive galaxy clusters (M > 2x10^{15} solar masses) can be well reproduced. We calculate the evolution with redshift of such a probability and find that giant radio halos can be power…
We derive the Ks-band luminosity function (LF) of the z=1.237 massive X-ray luminous cluster of galaxies RDCS J1252.9-2927. Photometric redshifts, derived from deep multi-wavelength BVRIzJKs data, and calibrated using a large subset of galaxies with spectroscopic redshifts, are used to separate the cluster galaxy population from the foreground and background field galaxy population. This allows for a simultaneous determination of the characteristic magnitude Ks* and faint end slope alpha of the LF without having to make an uncertain statistical background subtraction. The shape of the bright e…
We investigate a hierarchical structure formation scenario describing the evolution of a Super Massive Black Holes (SMBHs) population. The seeds of the local SMBHs are assumed to be 'pregalactic' black holes, remnants of the first POPIII stars. As these pregalactic holes become incorporated through a series of mergers into larger and larger halos, they sink to the center owing to dynamical friction, accrete a fraction of the gas in the merger remnant to become supermassive, form a binary system, and eventually coalesce. A simple model in which the damage done to a stellar cusps by decaying BH …
The annihilation of weakly interacting massive particles can provide an important heat source for the first (Pop. III) stars, potentially leading to a new phase of stellar evolution known as a "Dark Star". When dark matter (DM) capture via scattering off of baryons is included, the luminosity from DM annihilation may dominate over the luminosity due to fusion, depending on the DM density and scattering cross-section. The influx of DM due to capture may thus prolong the lifetime of the Dark Stars. Comparison of DM luminosity with the Eddington luminosity for the star may constrain the stellar m…
