We aim at reproducing the mass- and sigma-[alpha/Fe] relations in the stellar populations of early-type galaxies by means of a cosmologically motivated assembly history for the spheroids. We implement a detailed treatment for the chemical evolution of H, He, O and Fe in GalICS, a semi-analytical model for galaxy formation which successfully reproduces basic low- and high-redshift galaxy properties. The contribution of supernovae (both type Ia and II) as well as low- and intermediate-mass stars to chemical feedback are taken into account. We find that this chemically improved GalICS does not produce the observed mass- and sigma-[alpha/Fe] relations. The slope is too shallow and scatter too large, in particular in the low and intermediate mass range. The model shows significant improvement at the highest masses and velocity dispersions, where the predicted [alpha/Fe] ratios are now marginally consistent with observed values. We show that this result comes from the implementation of AGN (plus halo) quenching of the star formation in massive haloes. A thorough exploration of the parameter space shows that the failure of reproducing the mass- and sigma-[alpha/Fe] relations can partly be attributed to the way in which star formation and feedback are currently modelled. The merger process is responsible for a part of the scatter. We suggest that the next generation of semi-analytical model should feature feedback (either stellar of from AGN) mechanisms linked to single galaxies and not only to the halo, especially in the low and intermediate mass range. The integral star formation history of a single galaxy determines its final stellar [alpha/Fe] as it might be expected from the results of closed box chemical evolution models. (abridged)
This paper illustrates how mock observational samples of high-redshift galaxies with sophisticated selection criteria can be extracted from the predictions of GALICS, a hybrid model of hierarchical galaxy formation that couples the outputs of large cosmological simulations and semi-analytic recipes to describe dark matter collapse and the physics of baryons respectively. As an example of this method, we focus on the properties of Lyman Break Galaxies at redshift 3. With the MOMAF software package described in a companion paper, we generate a mock observational sample with selection criteria as…
High-resolution N-body re-simulations of 15 massive (10^{14}-10^{15} Msun) dark matter haloes have been combined with the hybrid galaxy formation model GalICS (Hatton et al. 2003), to study the formation and evolution of galaxies in clusters, within the framework of the hierarchical merging scenario. New features in GalICS include a better description of galaxy positioning within dark matter haloes, a more reliable computation of the temperature of the inter-galactic medium as a function of redshift, and a description of the ram pressure stripping process. We focus on the luminosity functions,…
In this paper we present a quantitative analysis of the chemical abundances in "monolithic" N-body-Tree-SPH models of elliptical galaxies to determine whether the ratio [alpha/Fe] increases with the galaxy mass as suggested by observational data.
We complement our study of alpha/Fe enhanced stellar population models of Lick absorption indices (Thomas et al. 2003) by comparing two sets of alpha/Fe enhanced models. In both models the impact on Lick indices due to alpha/Fe enhancement is accounted for through a modification of the stellar absorption line-strengths using the response functions of Tripicco & Bell (1995). One set of models, however, uses solar-scaled, the other alpha/Fe enhanced stellar evolutionary tracks. Since the alpha/Fe enhanced tracks are hotter than the solar-scaled ones (Salasnich et al. 2000), the correspondent ste…
We report an ultra-high-resolution simulation that follows evolution from the earliest stages of galaxy formation through the period of dynamical relaxation. The bubble structures of gas revealed in our simulation ($< 3\times 10^8$ years) resemble closely the high-redshift Lyman $α$ emitters (LAEs). After $10^9$ years these bodies are dominated by stellar continuum radiation and look like the Lyman break galaxies (LBGs) known as the high-redshift star-forming galaxies at which point the abundance of elements appears to be solar. After $1.3\times10^{10}$ years, these galaxies resemble present-d…
We explore the formation of alpha-enhanced and metal-rich stellar populations in the nuclei of luminous ellipticals under the assumption of two extreme galaxy formation scenarios based on hierarchical clustering, namely a fast clumpy collapse and the merger of two spirals. We investigate the parameter space of star formation time-scale, IMF slope, and stellar yields. In particular, the latter add a huge uncertainty in constraining time-scales and IMF slopes. We find that -- for Thielemann, Nomoto & Hashimoto nucleosynthesis -- in a fast clumpy collapse scenario an [alpha/Fe] overabundance of a…
The scope of this paper is two-fold: i) to test and improve our previous models of an outside-in formation for the majority of ellipticals in the context of the SN-driven wind scenario, by means of a careful study of gas inflows/outflows; ii) to explain the observed slopes, either positive or negative, in the radial gradient of the mean stellar [alpha/Fe], and their apparent lack of any correlation with all the other observables. In order to pursue these goals we present a new class of hydrodynamical simulations for the formation of single elliptical galaxies in which we implement detailed pre…
Synthetic Lick indices (e.g. Mg_2, Fe, etc.) of Simple Stellar Population (SSP) models are calibrated for the first time up to solar metallicity with a sample of Milky Way globular clusters (GCs) which includes the metal rich GCs of the Galactic bulge. This metallicity range is relevant to elliptical galaxies. It is shown that the Bulge GCs and integrated light follow the same correlation between Mg and Fe indices of elliptical galaxies, showing weaker Fe indices at given Mg indices with respect to models that assume solar-scaled abundances. This similarity is the robust empirical evidence for…
We investigate the metal enrichment of elliptical galaxies in the framework of hierarchical models of galaxy formation. The semi-analytical model we use in this Letter, which has been used to study the metal enrichment of the intracluster medium (ICM) by Nagashima et al., includes the effects of flows of gas and metals both into and out of galaxies and the processes of metal enrichment due to both type Ia and type II supernovae. We adopt a solar neighbourhood IMF for star formation in discs, but consider models in which starbursts have either a solar neighbourhood IMF or a top-heavy IMF. We fi…
Recent observations of the line of sight velocity profile of elliptical galaxies have furnished controversial results with some works favouring the presence of a large amount of dark matter in the outer regions and others arguing in favour of no dark matter at all. In order to shed new light on this controversy, we propose here a new phenomenological description of the total mass profile of galaxies. Under the hypothesis of spherical symmetry, we assume a double power-law expression for the global M/L ratio Upsilon(r)= Upsilon_0(r/r_0) ^{alpha}(1+r/r_0)^{beta}. In particular, Upsilon propto r^…
The spatial distributions of the mean luminosity-weighted stellar age, metallicity, and alpha/Fe ratio along both photometric axes of two nearby elliptical galaxies have been obtained using Lick index measurements on long slit spectra in order to reconstruct the star formation history in their kinematically distinct subsystems. Lick indexes were compared with those of single-aged stellar population (SSP) models. A population synthesis method was also applied in order to help disentangling the age-metallicity degeneracy. The stars characteristics are associated with their kinematics: they are o…
There are strong indications from recent papers (e.g. Worthey et al. 1992) that the abundance ratio of Mg/Fe, and consequently also O/Fe in giant elliptical galaxies is not solar. The line strengths of two Fe lines at 5270 and 5335 A are weaker than one expects from the strength of the Mg b line if [Mg/Fe] = 0. We have synthesized absorption line indices to derive the Mg and Fe abundances of these galaxies. For these models we have calculated new evolutionary tracks of high metallicity stars with a range of Mg/Fe abundances. This is the first time that such tracks have been generated. Integrat…
We have used the visible integral-field replicable unit spectrograph prototype (VIRUS-P), a new integral field spectrograph, to study the spatially and spectrally resolved Lyman-alpha emission line structure in the radio galaxy B2 0902+34 at z=3.4. We observe a halo of Lyman-alpha emission with a velocity dispersion of 250 km/s extending to a radius of 50 kpc. A second feature is revealed in a spatially resolved region where the line profile shows blueshifted structure. This may be viewed as either HI absorption at -450 km/s or secondary emission at -900 km/s from the primary peak. Our new dat…
High redshift radio galaxies (z>2) are believed to be progenitors of the giant ellipticals of today. They are often associated with giant Ly-alpha nebulae (sometimes >100 kpc), which have been for more than two decades valuable sources of information about the evolutionary status of the host galaxy and its chemical enrichment and star formation histories. I present in this paper a summary of the most relevant results about the giant nebulae obtained in the last ~10 years and the implications on our understanding of the early phases of evolution of massive elliptical galaxies.
Context: The spatial distribution of the stellar populations inside a spheroidal system and their kinematical properties supply important informations about the formation process. Aims: We have performed a detailed stellar population analysis using long slit spectroscopic observations up to almost one effective radius of two different early-type galaxies of low density regions of the local Universe: NGC 1052, a E4 Liner prototype of a loose group that has a stellar rotating disc, and NGC 7796, a E1 of the field which shows a kinematically distinct core. The mean luminosity-weighted stellar age…
The luminosities of the centers of nearby elliptical galaxies are very low compared to models of thin disc accretion to their black holes at the Bondi rate, typically a few hundredths to a few tenths of a solar mass per year. This has motivated models of inefficiently-radiated accretion that invoke weak electron-ion thermal coupling, and/or inhibited accretion rates due to convection or outflows. Here we point out that even if such processes are operating, a significant fraction of the accreting gas is prevented from reaching the central black hole because it condenses into stars in a gravitat…
NGC 4649 (M60) is one of a handful of giant Virgo ellipticals. We have obtained Gemini/GMOS spectra for 38 GCs associated with this galaxy. Applying the multi-index chi^2 minimisation technique of Proctor & Sansom (2002) with the single stellar population models of Thomas, Maraston & Korn (2004) we derive ages, metallicities and alpha-element abundance ratios. We find several young (2--3 Gyr old) super-solar metallicity GCs, while the majority are old (>10 Gyrs), spanning a range of metallicities from solar to [Z/H]=-2. At least two of these young GCs are at large projected radii of 17-20 kpc.…
The chemical enrichment and stellar abundance ratios of galaxies which form in a hierarchical clustering scheme are calculated. For this purpose I adopt the star formation histories (SFH) as they are delivered by semi-analytic models in Kauffmann (1996}. It turns out that the average SFH of cluster ellipticals does not yield globally alpha-enhanced stellar populations. The star burst that occurs when the elliptical forms in the major merger plays therefore a crucial role in producing alpha-enhancement. Only under the assumption that the IMF is significantly flattened with respect to the Salpet…
We compare [alpha/Fe], metallicity, and age distributions of globular clusters in elliptical, lenticular, and spiral galaxies, which we derive from Lick line index measurements. We find a large number of globular clusters in elliptical galaxies that reach significantly higher [alpha/Fe] values (>0.5) than any clusters in lenticular and spiral galaxies. Most of these extremely alpha-enriched globular clusters are old (t > 8 Gyr) and cover the metallicity range -1 <~ [Z/H] <~ 0. A comparison with supernova yield models suggests that the progenitor gas clouds of these globular clusters must have …
We introduce analytical expressions for a pseudo fully analytical elliptical projected Navarro, Frenk & White (NFW) mass profile to be used in lensing equations. We propose a formalism that incorporates the ellipticity into the expression for the lens potential, producing a pseudo-elliptical mass distribution. This approach can be implemented to any circular mass profile for which the projected mass profile Sigma(r) and the deflection angle profile alpha(r) both have analytical expressions; however the potential does not necessarily need to take an analytical form. We apply this new formalism …
In this work we investigate the stellar population, metallicity distribution and ionized gas in the elliptical galaxy NGC 5044, using long-slit spectroscopy and a stellar population synthesis method. We found differences in the slope of metal-line profiles along the galaxy which suggests an enhancement of alpha elements, particularly towards the central region. The presence of a non-thermal ionization source, such as a low-luminosity AGN and/or shock ionization, is implied by the large values of the ratio (N II])Ha observed in all sampled regions. However, the emission lines observed in the ex…
In models of galaxy formation in a hierarchical Universe, elliptical galaxies form through the merging of smaller disk systems. These models yield a number of testable predictions if reliable techniques for determining the relative ages and compositions of the stellar populations of different galaxies can be found: 1) ellipticals in low-density environments form later than ellipticals in clusters, 2) more massive ellipticals form later, 3) more massive ellipticals form in dissipationless mergers from disk galaxies with low gas content. While colours and the Balmer line strengths of galaxies ca…
We study the nature of Damped Lyman -Alpha systems (DLAs) by means of a comparison between observed abundances and models of chemical evolution of galaxies of different morphological type. In particular, we compare for the first time the abundance ratios as functions of metallicity and redshift with dust-corrected data. We have developed detailed models following the evolution of several chemical elements (H, D, He, C, N, O, Ne, Mg, Si, S, Fe, Ni and Zn) for elliptical, spiral and irregular galaxies. Each of the models is calibrated to reproduce the main features of a massive elliptical, the M…
Results from IRAS and recent X-ray and optical surveys are reviewed to discuss the properties and nature of the interstellar medium in elliptical galaxies. As to the dust component, there is a strong contrast with the situation among spiral galaxies in that masses of dust in ellipticals as derived from optical extinction are an order of magnitude LOWER than those derived from IRAS data. This dilemma can be resolved by assuming an extra, extended, diffusely distributed component of dust which is not detectable in optical data. Bona-fide global correlations among ISM components ---and between io…
We compute new population synthesis models of Lick absorption line indices with variable alpha/Fe ratios and use them to derive average ages, metallicities, and alpha/Fe element enhancements for a sample of 126 field and cluster early-type galaxies. Calibrating the models on galactic globular clusters, we show that any population synthesis model being based on stellar libraries of the Milky Way is intrinsically biased towards super-solar alpha/Fe ratios at metallicities below solar. We correct for this bias, so that the models presented here reflect constant alpha/Fe ratios at all metallicitie…
We present Hubble Space Telescope (HST) and ground-based observations of a pair of galaxies at redshift 2.38, which are collectively known as 2142-4420 B1 (Francis et al. 1996). The two galaxies are both luminous extremely red objects (EROs), separated by 0.8 arcsec. They are embedded within a 100 kpc scale diffuse Ly-alpha nebula (or blob) of luminosity ~10^44 erg/s. The radial profiles and colors of both red objects are most naturally explained if they are young elliptical galaxies: the most distant yet found. It is not, however, possible to rule out a model in which they are abnormally comp…
We present the result of a photometric and Keck-LRIS spectroscopic study of dwarf galaxies in the core of the Perseus Cluster, down to a magnitude of M_B = -12.5. Spectra were obtained for twenty-three dwarf-galaxy candidates, from which we measure radial velocities and stellar population characteristics from absorption line indices. From radial velocities obtained using these spectra we confirm twelve systems as cluster members, with the remaining eleven as non-members. Using these newly confirmed cluster members, we are able to extend the confirmed colour-magnitude relation for the Perseus C…
We present high-quality, Keck spectroscopic data for a sample of 20 globular clusters (GCs) in the massive E0 galaxy NGC1407. A subset of twenty line-strength indices of the Lick/IDS system have been measured for both the GC system and the central integrated star-light of the galaxy. Ages, metallicities and [alpha/Fe] ratios have been derived using several different approaches. The majority GCs in NGC1407 studied are old, follow a tight metallicity sequence reaching values slightly above solar, and exhibit mean [alpha/Fe] ratios of ~ 0.3 dex. In addition, three GCs are formally derived to be y…
We present spatially-resolved internal kinematics and stellar chemical abundances for a sample of dwarf elliptical (dE) galaxies in the Virgo Cluster observed with Keck/ESI. We find that 4 out of 17 dEs have major axis rotation velocities consistent with rotational flattening, while the remaining dEs have no detectable major axis rotation. Despite this difference in internal kinematics, rotating and non-rotating dEs are remarkably similar in terms of their position in the Fundamental Plane, morphological structure, stellar populations, and local environment. We present evidence for faint under…
I review the current understanding of the origin and nature of ``warm'' ionized gas in giant elliptical galaxies in the light of results of recent imaging and spectroscopic surveys. CCD imaging surveys have revealed that emission-line disks or filaments are (as a rule) associated with dust absorption, even in the X-ray brightest systems. This strongly suggests that the origin of this ionized gas is generally not through ``cooling flows''; galaxy interactions are favored instead. Using data from a new spectrophotometric survey of ``normal'' elliptical galaxies covering the whole optical range, …
By means of detailed chemical evolution models for galaxies of different morphological types (i.e. spirals, irregular/starburst galaxies and ellipticals) we study the nature of Damped Lyman-Alpha systems. Our concern is to infer which systems represent likely candidates for the DLA population and which do not. By focusing on individual systems, we can derive some constraints on both the nature of the associated galaxy and its age. Our results indicate that, owing to their high metallicities and [alpha/Fe] ratios, big spheroids represent unlikely DLA candidates whereas spirals (observed at diff…
We examine the K shell emission lines produced by isothermal and simple multiphase models of the hot gas in elliptical galaxies and galaxy clusters to determine the most effective means for constraining the width of the differential emission measure (xi(T)) in these systems which we characterize by a dimensionless parameter, sigma_xi. Comparison of line ratios of two-temperature (sigma_xi << 1) and cooling flow (sigma_xi ~1) models is presented in detail. We find that a two-temperature model can approximate very accurately a cooling flow spectrum over 0.5-10 keV. We have re-analyzed the ASCA s…
We present kinematics and stellar population properties of 17 dwarf early-type galaxies in the luminosity range -14> M_B> -19. Our sample fills the gap between the intensively studied giant elliptical and Local Group dwarf spheroidal galaxies. The dwarf ellipticals of the present sample have constant velocity dispersion profiles within their effective radii and do not show significant rotation, hence are clearly anisotropic. The dwarf lenticulars, instead, rotate faster and are, at least partially, supported by rotation. From optical Lick absorption indices, we derive metallicities and element…
We present UBVRI surface photometry for 16 dwarf elliptical galaxies in the Virgo Cluster with previously measured kinematic properties. The global optical colors are red, with median values for the sample of 0.24 +/- 0.03 in (U-B), 0.77 +/- 0.02 in (B-V), and 1.02 +/- 0.03 in (V-I). We recover the well known color-magnitude relation for cluster galaxies, but find no significant difference in dominant stellar population between rotating and non-rotating dwarf elliptical galaxies; the average age of the dominant stellar population is 5-7 Gyr in all 16 galaxies in this sample. Analysis of optica…
I discuss the formation of alpha-enhanced metal-rich stellar populations in the nuclei of luminous ellipticals. Based on hierarchical clustering, different galaxy formation scenarios, which imply different star formation histories, are considered. In contrast to the fast clumpy collapse mode, the late merger of two spiral galaxies fails to reproduce significantly $α$-enhanced abundance ratios, unless the IMF is flattened. Following the star formation history predicted by semi-analytic models of hierarchical clustering for the average elliptical, solar abundance ratios are obtained with Salpete…
We have studied the effects of an hypothetical initial generation containing very massive stars (M > 100 Msun, pair-creation SNe) on the chemical and photometric evolution of elliptical galaxies. To this purpose, we have computed the evolution of a typical elliptical galaxy with luminous mass of the order of 10^11 Msun and adopted chemical evolution models already tested to reproduce the main features of ellipticals. We have tested several sets of yields for very massive zero-metallicity stars: these stars should produce quite different amounts of heavy elements than lower mass stars. We found…
We have obtained Gemini/GMOS spectra for 22 GCs associated with NGC 3379. We derive ages, metallicities and alpha-element abundance ratios from simple stellar population models using the multi-index chi^2 minimisation method of Proctor & Sansom (2002). All of these GCs are found to be consistent with old ages, i.e. >10 Gyr, with a wide range of metallicities. A trend of decreasing alpha-element abundance ratio with increasing metallicity is indicated. The projected velocity dispersion of the GC system is consistent with being constant with radius. Non-parametric, isotropic models require a sig…
We present the detection of nuclear stellar discs in the low-luminosity elliptical galaxies NGC 4458 and NGC 4478, which are known to host a kinematically-decoupled core. Using archival HST imaging, and available absorption line-strength index data based on ground-based spectroscopy, we investigate the photometric parameters and the properties of the stellar populations of these central structures. Their scale length, h, and face-on central surface brightness, mu_0^c, fit on mu_0^c-h relation for galaxy discs. For NGC 4458 these parameters are typical for nuclear discs, while the same quantiti…
Elliptical galaxies probably host the most metal rich stellar populations in the Universe. The processes leading to both the formation and the evolution of such stars are discussed by means of a new gas dynamical model which implements detailed chemical evolution prescriptions. Moreover, the radial variations in the metallicity distribution of these stars are investigated by means of G-dwarf-like diagrams. By comparing model predictions with observations, we derive a picture of galaxy formation in which the higher is the mass of the galaxy, the shorter are the infall and the star formation tim…
We present the results of a Keck spectroscopic study of globular clusters associated with the Virgo Cluster dwarf elliptical VCC 1386. We analyze blue spectroscopic absorption lines from 3500-5500 A for 13 globular cluster candidates and confirm that five are associated with VCC 1386. By comparing metal and Balmer line indices of these globular clusters with alpha-enhanced single stellar population models we find that these systems are metal poor with [Fe/H] < -1.35 and old, with ages > 5 Gyr at 3 sigma confidence, placing their formation at z >1. This is one of the first spectroscopic studies…
The globular cluster luminosity function, specific globular cluster frequency, S_N, specific globular cluster mass, T_MP, and globular cluster mass fraction in dwarf elliptical galaxies are explored using the full 69 galaxy sample of the HST WFPC2 Dwarf Elliptical Galaxy Snapshot Survey. The GCLFs of the dEs are well-represented with a t_5 function with a peak at M_{V,Z}^0(dE,HST) = -7.3 +/- 0.1. This is ~0.3 magnitudes fainter than the GCLF peaks in giant spiral and elliptical galaxies, but the results are consistent within the uncertainties. The bright-end slope of the luminosity distributio…
We have previously introduced the parameter `alpha' as an indicator of stability to m=2 nonaxisymmetric modes in rotating, self-gravitating, axisymmetric, gaseous and stellar systems. This parameter can be written as a function of the total rotational kinetic energy, the total gravitational potential energy, and as a function of the topology/connectedness and the geometric shape of a system. Here we extend the stability criterion to nonaxisymmetric equilibrium systems, such as ellipsoids and elliptical disks and cylinders. We test the validity of this extension by considering predictions for p…
Recently, Allen et al. measured a tight correlation between the Bondi accretion rates and jet powers of the nuclei of nearby X-ray luminous elliptical galaxies. We employ two models of jet powering to understand the above correlation and derive constraints on the spin and accretion rate of the central black holes. The first is the Blandford-Znajek model, in which the spin energy of the hole is extracted as jet power; the second model is an hybrid version of the Blandford-Payne and Blandford-Znajek processes, in which the outflow is generated in the inner parts of the accretion disk. We assume …
We have computed the higher-order Balmer absorption line indices Hgamma and Hdelta (Worthey & Ottaviani 1997) for stellar population models with variable element ratios. The response of these indices to abundance ratio variations is taken from detailed line formation and model atmosphere calculations. We find that Hgamma and Hdelta, unlike Hbeta, are very sensitive to alpha/Fe ratio changes at super-solar metallicities. Both line indices increase significantly with increasing alpha/Fe ratio. This effect cannot be neglected when these line indices are used to derive the ages of metal-rich, unre…
We present arguments based on the measured abundances in individual damped Lyman alpha systems (DLAs) and sub-damped Lyman alpha systems (sub-DLAs), and also the average abundances inferred in large samples of QSO absorption line systems, to suggest that the amount of dust in intervening QSO absorbers is small and is not responsible for missing many QSOs in magnitude limited QSO surveys. While we can not totally rule out a bimodal dust distribution with a population of very dusty, metal rich, absorbers which push the background QSOs below the observational threshold of current optical spectros…
Long-baseline interferometric observations obtained with the Navy Prototype Optical Interferometer of the H-alpha-emitting envelopes of the Be stars eta Tauri and beta Canis Minoris are presented. For compatibility with the previously published interferometric results in the literature of other Be stars, circularly symmetric and elliptical Gaussian models were fitted to the calibrated H-alpha observations. The models are sufficient in characterizing the angular distribution of the H-alpha-emitting circumstellar material associated with these Be stars. To study the correlations between the vari…
Dwarf galaxies, as the most numerous type of galaxy, offer the potential to study galaxy formation and evolution in detail in the nearby Universe. Although they seem to be simple systems at first view, they remain poorly understood. In an attempt to alleviate this situation, the MAGPOP EU Research and Training Network embarked on a study of dwarf galaxies named MAGPOP-ITP (Peletier et al., 2007). In this paper, we present the analysis of a sample of 24 dwarf elliptical galaxies (dEs) in the Virgo Cluster and in the field, using optical long-slit spectroscopy. We examine their stellar populatio…
We have analyzed the far-ultraviolet (FUV) spectra of six elliptical and S0 galaxies in order to characterize their hot stellar populations. The spectra were obtained using the Hopkins Ultraviolet Telescope (HUT) in March 1995. These data, together with the spectra of two galaxies observed with HUT in 1990, represent the only FUV spectra of early type galaxies that extend to the Lyman limit at 912 A and therefore include the "turnover" in the spectral energy distribution below Lyman alpha. Using an extensive new grid of synthetic spectra which match the HUT resolution and cover the relevant pa…
We report the first observations of the clustering environment of damped Lyman alpha absorption systems at z=4. Color selection and photometric redshifts were used to select 44 candidate Lyman-break galaxies brighter than I_AB=25.5 from deep BRI images of the 35 sq. arcmin field containing the quasar BR 0951-04. Multislit spectroscopy of 35 candidate galaxies was performed and 8 of these candidates have been confirmed as z>3.5 Lyman-break galaxies. With only BRI photometry, the photometric redshifts are quite accurate for the spectroscopically confirmed galaxies but have a high rate of misclas…
We present measurements of the near-infrared Calcium II triplet (CaT, CaT*), Paschen (PaT) and Magnesium (MgI) indices for a well-studied sample of 19 bulges of early to intermediate spiral galaxies. We find that both the CaT* and CaT indices decrease with central velocity dispersion (sigma) with small scatter. This dependence is similar to that recently found by Cenarro (2002) for elliptical galaxies, implying an uniform CaT* -- sigma relation that applies to galaxies from ellipticals to intermediate-type spirals. The decrease of CaT and CaT* with sigma contrasts with the well-known increase …
We derive the scatter in the relationship between redshift and radio-to-submm spectral index, alpha^{350}_{1.4}, using the observed spectral energy distributions of 17 low redshift star forming galaxies. A mean galaxy model is derived, along with the rms scatter in alpha^{350}_{1.4}. The scatter is roughly constant with redshift. Constant rms scatter, combined with the flattening of the mean alpha^{350}_{1.4} -- z relationship with increasing redshift, leads to increasing uncertainty for redshift estimates at high redshifts. Normalizing by the dust temperature in the manner proposed by Blain d…
Spectrophotometry and imaging of the two planetary nebulae He2-436 and Wray16-423, recently discovered to be in the Sagittarius dwarf elliptical galaxy, are presented. Wray16-423 is a high excitation planetary nebula (PN) with a hot central star. In contrast He2-436 is a high density PN with a cooler central star and evidence of local dust, the extinction exceeding that for Wray16-423 by E(B-V)=0.28. The extinction to Wray16-423, (E(B-V)=0.14), is consistent with the extinction to the Sagittarius (Sgr) Dwarf. Both PN show Wolf-Rayet features in their spectra, although the lines are weak in Wra…
We present near-IR spectroscopy of three Extremely Red Objects (EROs) using the OHS/CISCO spectrograph at Subaru telescope. One target exhibits a strong emission line which we identify as H-alpha at z = 1.34. Using new and existing ground-based optical and near-IR imaging, and archival HST imaging, we argue that this target is essentially an elliptical galaxy, with an old stellar population of around 4E11 solar masses, but having a dust-enshrouded star-forming component with a SFR of some 50--100 solar masses per yr. There is no evidence that the galaxy contains an AGN. Analysis of a further t…
We present line strengths in the bulges and inner disks of 38 galaxies in the local universe, including several galaxies whose bulges were previously identified as being disk-like in their colors or kinematics, to see if their spectral properties reveal evidence for secular evolution. We find that red bulges of all Hubble types are similar to luminous ellipticals in their central stellar populations. They have large luminosity-weighted ages, metallicities, and alpha/Fe ratios. Blue bulges can be separated into a metal-poor class that is restricted to late-types with small velocity dispersion a…
The power of jets from black holes are expected to depend on both the spin of the black hole and the structure of the accretion disk in the region of the last stable orbit. We investigate these dependencies using two different physical models for the jet power: the classical Blandford-Znajek (BZ) model and a hybrid model developed by Meier. In the BZ case, the jets are powered by magnetic fields directly threading the spinning black hole while in the hybrid model, the jet energy is extracted from both the accretion disk as well as the black hole via magnetic fields anchored to the accretion fl…
We present a study of the H$α$ line emission from a sample of 1482 optically-selected, morphologically-classified bright galaxies (median redshift of 0.05) derived from the Sloan Digital Sky Survey. The luminosity function is calculated for each morphological class and for the total sample. The luminosity function fitted with the Schechter form gives a slope $α=-1.43\pm 0.10$ for the total sample and the H$α$ luminosity density is $10^{39.31\pm 0.04{+0.10\atop-0.07}}h$ erg s$^{-1}$Mpc$^{-3}$, where the first error is statistical and the second is systematic. This value is consistent with that …
We report the discovery of a group of galaxies at redshift 2.38. We imaged about 10% of a claimed supercluster of QSO absorption-lines at z=2.38 (Francis & Hewett 1993). In this small field (2 arcmin radius) we detect two Ly-alpha emitting galaxies. The discovery of two such galaxies in our tiny field supports Francis & Hewett's interpretation of the absorption-line supercluster as a high redshift "Great Wall". One of the Ly-alpha galaxies lies 22 arcsec from a background QSO, and may be associated with a multi-component Ly-alpha absorption complex seen in the QSO spectrum. This galaxy has an …
We examine whether isothermal models of the hot gas can successfully describe the ASCA and ROSAT spectra of NGC 1399, NGC 4472, NGC 4636, and NGC 5044. Broad-band spectral fitting of the ASCA SIS and GIS data accumulated within a radius of ~5 arcmin for each galaxy shows that isothermal models are unable to fit the SIS data near 1 keV. In addition, these isothermal models typically fail to produce the large equivalent widths of the K-alpha line blends of the H-like and He-like ions of Si and S which are measured independently of the Fe L emission lines. Two-temperature models provide excellent…
Based on FORS2-VLT long-slit spectroscopy, the analysis of the central absorption line indices of 9 S0 galaxies in the Fornax Cluster is presented. Central indices correlate with central velocity dispersions as observed in ellipticals. However, the stellar population properties of these S0s indicates that the observed trends are produced by relative differences in age and alpha-element abundances and not in metallicity ([Fe/H]) as previous studies have found in elliptical galaxies. The observed scatter in the line indices vs. velocity dispersion relations can be partially explained by the rota…
We present a new class of hydrodynamical models for the formation of bulges (either massive elliptical galaxies or classical bulges in spirals) in which we implement detailed prescriptions for the chemical evolution of H, He, O and Fe. Our results hint toward an outside-in formation in the context of the supernovae-driven wind scenario. The build-up of the chemical properties of the stellar populations inhabiting the galactic core is very fast. Therefore we predict a non significant evolution of both the mass-metallicity and the mass-[alpha/Fe] relations after the first 0.5 - 1 Gyr. In this fr…
