Showing papers on "Brightest cluster galaxy published in 1995"
TL;DR: The Butcher-Oemler effect may reflect the typical evolution of galaxies in groups and in the field rather than the influence of clusters on star formation in galaxies as discussed by the authors, and the most likely environments for such interactions are poor groups, which have lower velocity dispersions than clusters and higher galaxy densities than the field.
Abstract: The violent star formation history of ``E+A'' galaxies and their detection almost exclusively in distant clusters is frequently used to link them to the ``Butcher-Oemler effect'' and to argue that cluster environment influences galaxy evolution. From 11113 spectra in the Las Campanas Redshift Survey, we have obtained a unique sample of 21 nearby ``E+A" galaxies. Surprisingly, a large fraction (about 75%) of these ``E+A''s lie in the field. Therefore, interactions with the cluster environment, in the form of the ICM or cluster potential, are not essential for ``E+A'' formation. If one mechanism is responsible for ``E+A''s, their existence in the field and the tidal features in at least 5 of the 21 argue that galaxy-galaxy interactions and mergers are that mechanism. The most likely environments for such interactions are poor groups, which have lower velocity dispersions than clusters and higher galaxy densities than the field. In hierarchical models, groups fall into clusters in greater numbers at intermediate redshifts than they do today. Thus, the Butcher-Oemler effect may reflect the typical evolution of galaxies in groups and in the field rather than the influence of clusters on star formation in galaxies. This abstract is abridged.
410 citations
TL;DR: In this article, a set of theoretical spectral energy distributions has been calculated for high and low-metallicity galaxies and essentially all relevant initial mass functions and star formation histories and it was shown that, on average, less than 3% of the intrinsic Lyman-continuum photons escape from the program galaxies.
Abstract: The starburst galaxies IRAS 08339+6517, Mrk 1267, Mrk 66, and Mrk 496 (=NGC 6090) were observed with the Hopkins Ultraviolet Telescope (HUT) during the Astro-2 mission. All four galaxies have radial velocities larger than 5000 km s-1, permitting the measurement of their intrinsic Lyman-continuum fluxes redward of the H I absorption edge in our Galaxy. The sample was selected on the basis of having the most favorable conditions for the escape of Lyman-continuum photons. Two σ upper limits of Fλ < 7 × 10-16 ergs s-1 cm-2 A-1 were obtained for the flux around 900 A within the rest frame of each galaxy. A set of theoretical spectral energy distributions has been calculated. We show that there exists a tight correlation between the continuum luminosity at 900 A and the total number of photons emitted in the Lyman continuum, which is valid for high- and low-metallicity galaxies and essentially all relevant initial mass functions and star formation histories. Comparison with the observed values suggests that, on average, less than 3% of the intrinsic Lyman-continuum photons escape from the program galaxies. Models for the ionization of the intergalactic medium at high z by young starbursts require a significant fraction of the ionizing radiation to escape from the galaxy. If the four galaxies observed by us have properties similar to young galaxies at redshift z ≈ 3, such galaxies are not likely to provide Lyman-continuum photons for the ionization of the early universe.
281 citations
TL;DR: In this article, a new method for measuring the projected mass distributions of galaxy clusters is presented, which is measured by comparing the joint distribution in redshift and magnitude of galaxies behind the cluster with that of field galaxies.
Abstract: We present a new method for measuring the projected mass distributions of galaxy clusters. The gravitational amplification is measured by comparing the joint distribution in redshift and magnitude of galaxies behind the cluster with that of field galaxies. We show that the total amplification is directly related to the surface mass density in the weak field limit, and so it is possible to map the mass distribution of the cluster. The method is shown to be limited by discreteness noise and galaxy clustering behind the lens. Galaxy clustering sets a lower limit to the error along the redshift direction, but a clustering independent lensing signature may be obtained from the magnitude distribution at fixed redshift. Statistical techniques are developed for estimating the surface mass density of the cluster. We extend these methods to account for any obscuration by cluster halo dust, which may be mapped independently of the dark matter. We apply the method to a series of numerical simulations and show the feasibility of the approach. We consider approximate redshift information, and show how the mass estimates are degraded.
273 citations
TL;DR: In this article, the authors investigated the Hoessel relationship between the metric luminosity, L(sub m), within the central 10 kpc/h of the BCGs and the logarithmic slope of the surface brightness profile, alpha.
Abstract: We investigate the use of brightest cluster galaxies (BCGs) as standard candles for measuring galaxy peculiar velocities on large scales. We have obtained precise large-format CCD surface photometry and redshifts for an all-sky, volume-limited (z less than or = 0.05) sample of 199 BCG. We reinvestigate the Hoessel (1980) relationship between the metric luminosity, L(sub m), within the central 10 kpc/h of the BCGs and the logarithmic slope of the surface brightness profile, alpha. The L(sub m)-alpha relationship reduces the cosmic scatter in L(sub m) from 0.327 mag to 0.244 mag, yielding a typical distance accuracy of 17% per BCG. Residuals about the L(sub m)-alpha relationship are independent of BCG luminosity, BCG B - R(sub c) color, BCG location within the host cluster, and richness of the host cluster. The metric luminosity is independent of cluster richness even before correcting for its dependence on alpha, which provides further evidence for the unique nature of the BCG luminosity function. Indeed, the BCG luminosity function, both before and after application of the alpha-correction, is consistent with a single Gaussian distribution. Half the BCGs in the sample show some evidence of small color gradients as a function of radius within their central 50 kpc/h regions but with almost equal numbers becoming redder as becoming bluer. However, with the central 10 kpc/h the colors are remarkably constant -- the mean B - R(sub c) color is 1.51 with a dispersion of only 0.06 mag. The narrow photometric and color distributions of the BCGs, the lack of 'second-parameter' effects, as well as the unique rich cluster environment of BCGs, argue that BCGs are the most homogeneous distance indicators presently available for large-scale structure research.
268 citations
252 citations
TL;DR: In this paper, the luminosity function (LF) of galaxies in the core of the Coma cluster was determined, assuming H_0=75 km/s/Mpc, a magnitude regime previously explored only in the Local Group.
Abstract: We determine the luminosity function (LF) of galaxies in the core of the Coma cluster for M_R<=-11.4 (assuming H_0=75 km/s/Mpc), a magnitude regime previously explored only in the Local Group. Objects are counted in a deep CCD image of Coma having RMS noise of 27.7 R mag~arcsec$^{-2}$. A correction for objects in the foreground or background of the Coma cluster---and the uncertainty in this correction---are determined from images of five other high-latitude fields, carefully matched to the Coma image in both resolution and noise level. Accurate counts of Coma cluster members are obtained as faint as R=25.5, or M_R=-9.4. The LF for galaxies is well fit by a power law dN/dL\propto L^\alpha, with \alpha=-1.42\pm0.05, over the range -19.4
236 citations
TL;DR: In this paper, the authors present a digital catalog of images of 113 galaxies in the "Third Reference Catalog of Bright Galaxies" (RC3) which is available through anonymous FTP from this ftp URL.
Abstract: We present a digital catalog of images of 113 galaxies in this paper. These galaxies are all nearby, bright, large and well resolved. All images were recorded with charge coupled devices (CCDs) at the Palomar Observatory with the 1.5 meter telescope and at the Lowell Observatory with the 1.1 meter telescope. At Palomar we used the Thuan--Gunn g, r and i photometric bands to take 3 images each of 31 spiral galaxies; at Lowell we used the B_J and R bands (2 images per galaxy) of the photometric system by Gullixson et al. (1995) to observe 82 spirals and ellipticals. The galaxies were selected to span the Hubble classification classes. All data are photometrically calibrated with foreground stars removed. Important data on these galaxies published in the "Third Reference Catalog of Bright Galaxies" (RC3) are recorded in the FITS file headers. All files are available through anonymous FTP from this ftp URL, through WWW at this http URL, and Princeton University Press will soon publish the data on CD-ROM.
202 citations
TL;DR: In this paper, the B-band Tully-Fisher relation for low surface brightness (LSB) galaxies was presented and the relation between scalelength and linewidth for LSB and normal galaxies was examined.
Abstract: We present the B-band Tully-Fisher relation for low surface brightness (LSB) galaxies. These LSB galaxies follow the same Tully-Fisher relation as normal spiral galaxies. This implies that the mass-to-light ratio (M/L) of LSB galaxies is typically a factor of 2 larger than that of normal galaxies of the same total luminosity and morphological type. Since the dynamical mass of a galaxy is related to the rotational velocity and scalelength via M proportional to V(2)h, at fixed linewidth LSB galaxies must be twice as large as normal galaxies. This is confirmed by examining the relation between scalelength and linewidth for LSB and normal galaxies. The universal nature of the Tully-Fisher relation can be understood if LSB galaxies are galaxies with low mass surface density, sigma ($) over bar. The mass surface density apparently controls the luminosity evolution of a galaxy in such a way as to keep the product sigma ($) over bar M/L constant.
194 citations
TL;DR: In this paper, the authors presented a galaxy count from deep VRI images obtained with the Keck Telescope, which reached R ~ 27 in median seeing FWHM 0.5-0.6, and they detected a integrated galaxy number density of 7 × 105 deg-2, equivalent to 3 × 10^(10) galaxies in the observable universe.
Abstract: We present faint galaxy counts from deep VRI images obtained with the Keck Telescope. These images reach R ~ 27 in median seeing FWHM ~ 0.”5-0.”6, and we detect a integrated galaxy number density of 7 × 105 deg-2, equivalent to 3 × 10^(10) galaxies in the observable universe. In addition we present median galaxy colors as a function of magnitude; bluing trends are visible in all colors to R ~ 24.5. Fainter than R ~ 24.5, however, the typical V - R color becomes redder again, V - I remains constant, and R - I becomes yet bluer. These trends are consistent with the VRI count slopes, implying a decrease in the V slope at the faintest levels, which our data support. Taking advantage of our good seeing we also present median half-light radii for faint galaxies; these show a steady decline at fainter magnitudes, leading to an intrinsic half-light radius of ~0 2 for a typical R ~ 26 galaxy. Irrespective of the redshift distribution, the extremely high galaxy surface densities and their small intrinsic sizes are consistent with a scenario in which the majority of the very faint field population are dwarf galaxies or subgalactic units.
163 citations
TL;DR: In this article, the authors presented very deep WFPC2 images in the F814W filter of two Hawaii Survey fields, SSA13 and SSA22, and compared the colors, star-forming properties and morphologies of the faintest galaxies with a reference sample of bright nearby galaxies and analyzed the changes in field galaxy morphology with magnitude.
Abstract: We present very deep $HST$ WFPC2 images in the F814W filter of two Hawaii Survey fields, SSA13 and SSA22. Using these data with previous ground-based imaging and spectroscopy, we compare the colors, star-forming properties and morphologies of the faintest galaxies with a reference sample of bright nearby galaxies and analyze the changes in field galaxy morphology with magnitude. Our principal result is the identification of a new morphological class of ``chain'' galaxies at the faintest magnitudes. Based on limited spectroscopy, we tentatively conclude that these are linearly organized giant star-forming regions at $z = 0.5-3$ and, if this is correct, that these are large galaxies in the process of formation.
161 citations
01 Jan 1995
TL;DR: In this article, the authors present results of surveys for high redshift galaxies selected by their having produced detectable Mg II and Lyman limit absorption in the spectra of background QSOs.
Abstract: We present results of surveys for high redshift galaxies selected by their having produced detectable Mg II and Lyman limit absorption in the spectra of background QSOs We discuss the properties of the absorbing galaxies, the connection between galaxy properties and absorption line signatures, and how a combination of QSO absorption line and conventional faint galaxy techniques can be used to study field galaxy evolution to very large redshifts
TL;DR: In this article, the authors used rest frame Stroemgren photometry (3500 A, 4100 A, 4750 A, and 5500 A) for 509 galaxies in 17 rich clusters between z = 0 and z = 1 as a test of color evolution.
Abstract: Rest frame Stroemgren photometry (3500 A, 4100 A, 4750 A, and 5500 A) is presented for 509 galaxies in 17 rich clusters between z = 0 and z = 1 as a test of color evolution. Our observations confirm a strong, rest frame, Butcher-Oemler effect where the fraction of blue galaxies increases from 20% at z = 0.4 to 80% at z = 0.9. We also find that a majority of these blue cluster galaxies are composed of normal disk or post-starburst systems based on color criteria. When comparing our colors to the morphological results from Hubble Space Telescope HST imaging, we propose that the blue cluster galaxies are a population of late-type, low surface brightness objects which fade and are then destroyed by the cluster tidal field. After isolating the red objects from Butcher-Oemler objects, we have compared the mean color of these old, non-star-forming objects with spectral energy distribution models in the literature as a test for passive galaxy evolution in ellipticals. We find good agreement with single-burst models which predict a mean epoch of galaxy formation at z = 5. Tracing the red envelope for ellipticals places the earliest epoch of galaxy formation at z = 10.
TL;DR: In this article, a large and well-controlled sample of clusters of galaxies was used to investigate the relation between cluster velocity dispersions and X-ray temperatures of intra-cluster gas.
Abstract: Using a large and well-controlled sample of clusters of galaxies, we investigate the relation between cluster velocity dispersions and X-ray temperatures of intra-cluster gas. In order to obtain a reliable estimate of the total velocity dispersion of a cluster, independent of the level of anisotropies in galaxy orbits, we analyze the integrated velocity dispersion profiles over increasing distances from the cluster centers. Distortions in the velocity fields, the effect of close clusters, the presence of substructures, and the presence of a population of (spiral) galaxies not in virial equilibrium with the cluster potential are taken into account. Using our final sample of 37 clusters, for which a reliable estimate of the velocity dispersion could be obtained, we derive a relation between the velocity dispersions and the X-ray temperatures, with a scatter reduced by more than 30 % with respect to previous works. A chi square fit to the temperature-velocity dispersion relation does not exclude the hypothesis that the ratio between galaxy and gas energy density (the so-called spectral beta) is a constant for all clusters. In particular, the value of beta=1, corresponding to energy equipartition, is acceptable.
TL;DR: In this paper, the authors investigated the relationship between central Mg b line strength and central velocity dispersion for seven elliptical and nine brightest cluster galaxies (BCGs) in order to study their stellar populations and investigate their relationship to one another.
Abstract: Line strengths and their gradients in Mg, Fe, and H beta have been determined for seven elliptical and nine brightest cluster galaxies (BCGs) in order to study their stellar populations and investigate their relationship to one another. We find that BCGs follow the same relationship between central Mg b line strength and central velocity dispersion found for elliptical galaxies. Brightest cluster galaxies are in agreement with the known trend toward more massive elliptical galaxies having larger [Mg/Fe] ratios, while the internal gradients within our BCG and E galaxies are consistent with a roughly constant [Mg/Fe] ratio. We find that a correlation exists between the central [Mg/Fe] ratio and average H beta line strength in the sense that both BCG and elliptical galaxies with larger [Mg/Fe] ratios have lower [H beta] strengths. For our sample, H beta is the best predictor of [Mg/Fe] ratio. If the dominant contribution to the H beta feature is from turnoff stars then this relation predicts that more massive elliptical galaxies are older than less massive ones. If, however, the main source of the H beta index is from horizontal-branch stars, then the observed {[Mg/Fe],H beta} relation could be the result of more massive elliptical galaxies having flatter IMFs for high-mass stars than less massive elliptical galaxies. The [H beta] line strengths of the objects in our sample span a range of values. The BCGs generally have low global H beta line strengths, which, under the assumption that the H beta feature can be used as an age discriminant, indicates that the bulk of these systems underwent their last major episode of star formation greater than or similar to 8-10 Gyr ago. For both the elliptical galaxies and BCGs we find that within a galaxy, the H beta profile is flat for objects whose H beta absorption can be reliably measured. In the presence of a declining metallicity gradient this suggests that the centers of elliptical galaxies and BCGs are similar to 1-3 Gyr younger than their outer regions. The metal line strength gradients for the elliptical galaxies and BCGs are similar and consistent with an average gradient of Delta[Fe/H]/Delta log r = -0.25 +/- 0.1, corresponding to a reduction in the mean metallicity of the stellar population by a factor of similar to 2 over a factor of 10 in radius. No strong correlations are found between the metallicity gradient sizes and either kinematic or line strength parameters of the galaxies. For the galaxy NGC 4073, the brightest member of the poor cluster MKW 4, we find enhanced H beta absorption in the region coincident with the counterrotating stellar core. These observations are consistent with a scenario in which the accreted object was a younger system and/or a recent episode of star formation was triggered by an interaction.
TL;DR: In this paper, a wide-field optical and near-IR (JHK) imaging is presented for two rich galaxy clusters: Abell~370 at 0.374 and Abell ~851 (Cl0939+47), where the colors of the E/S0s are bluer than those in the Bower et al. (1992) Coma sample in the optical-K$ color.
Abstract: Wide-field optical and near--IR ($JHK$) imaging is presented for two rich galaxy clusters: Abell~370 at $z=0.374$ and Abell~851 (Cl0939+47) at $z=0.407$. Galaxy catalogs selected from the near--IR images are 90\% complete to approximately 1.5 mag below $K^\ast$ resulting in samples with $\sim$100 probable member galaxies per cluster in the central $\sim$2 Mpc. Comparison with $HST$ WFPC images yields subsamples of $\sim$70 galaxies in each cluster with morphological types. Analysis of the complete samples and the $HST$ subsamples shows that the $z\sim 0.4$ E/S0s are bluer than those in the Bower et al.\ (1992) Coma sample in the optical$-K$ color by $0.13$~mag for Abell~370 and by $0.18$~mag for Abell~851. If real, the bluing of the E/S0 populations at moderate redshift is consistent with that calculated from the Bruzual and Charlot (1993) models of passive elliptical galaxy evolution. In both clusters the intrinsic scatter of the known E/S0s about their optical$-K$ color--mag relation is small ($\sim 0.06$ mag) and not significantly different from that of Coma E/S0s as given by Bower et al.\ (1992), indicating that the galaxies within each cluster formed at the same time at an early epoch.
TL;DR: In this article, the spatial distribution of substructure in clusters of galaxies using Einstein X-ray observations was examined and it was found that subclusters have a markedly anisotropic distribution that reflects the surrounding matter distribution on supercluster scales.
Abstract: We have examined the spatial distribution of substructure in clusters of galaxies using Einstein X-ray observations. Subclusters are found to have a markedly anisotropic distribution that reflects the surrounding matter distribution on supercluster scales. Our results suggest a picture in which cluster formation proceeds by mergers of subclusters along large-scale filaments. The implications of such an anisotropic formation process for the shapes, orientations, and kinematics of clusters are discussed briefly.
TL;DR: In this paper, the Butcher-Oemler effect is explained by the evolution of the galaxies in the universe hierarchically, and it is shown that a rich cluster observed at high redshift has a significantly different evolutionary history to a cluster of the same richness observed today.
Abstract: We show that the rapid evolution in the fraction of blue, star-forming galaxies seen in clusters as a function of redshift (the Butcher-Oemler effect) can be explained very simply if structure formation in the universe proceeeds hierarchically. We show that a rich cluster observed at high redshift has had a significantly different evolutionary history to a cluster of the same richness observed today. High redshift clusters take longer to assemble and thus under- go more merging at small lookback times. We have investigated two models of star formation in cluster galaxies: 1) a model in which star formation is induced by galaxy-galaxy mergers and interactions and 2) a model in which star formation is regulated by the infall of galaxies onto larger systems such as groups and clusters. Both models produce trends consistent with the Butcher- Oemler effect. Our models of cluster formation and evolution allow us to make predictions about trends in the observed properties of clusters with redshift. We find that there should be a correlation between the mass of the cluster or group and the strength of the observed Butcher-Oemler effect, with more massive systems exhibiting more evolution than less massive systems. We also predict that both the blue galaxy fraction and the incidence of interacting galaxies in rich clusters should rise continuously with redshift. Finally, we have explored the influence of cosmological parameters on our predictions for cluster evolution. We find that models in which structure formation occurs at very early epochs, such as low $\Omega$ models, predict rather little recent star formation and merging activity in clusters at redshifts of around 0.4.
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TL;DR: In this article, the authors presented new counts of eld galaxies from more than 20 square arcminutes to a limiting magnitude of K=20 and from 2 square arc minutes to K=21.5.
Abstract: We present new counts of eld galaxies from more than 20 square arcminutes to a limiting magnitude of K=20 and from 2 square arcminutes to K=21.5. At the faintest magnitudes the counts are slightly higher than those reported previously, though still consistent given the small numbers of galaxies in the two samples.
TL;DR: In this paper, it has been shown that a considerable fraction of the massive star formation in the universe occurred at z 1 field galaxies, and that the era from redshifts 1 to 2 was clearly a major period of galaxy formation.
Abstract: The complex problem of when and how galaxies formed has not until recently been susceptible of direct attack It has been known for some time that the excessive number of blue galaxies counted at faint magnitudes implies that a considerable fraction of the massive star formation in the universe occurred at z 1 field galaxies, we can now show directly that in fact these forming galaxies are present in substantial numbers at B \sim 24, and that the era from redshifts 1 to 2 was clearly a major period of galaxy formation These z > 1 galaxies have very unusual morphologies as seen in deep HST WFPC2 images
TL;DR: In this paper, a sample of 13 brightest duster galaxies (BCGs) was used to study their internal stellar kinematics and investigate their relationship to elliptical galaxies, finding that BCGs generally display velocity dispersion profiles with gradients similar to those found in normal bright ellipticals.
Abstract: Velocity dispersion profiles and rotation curves have been determined for a sample of 13 brightest duster galaxies (BCGs) in order to study their internal stellar kinematics and investigate their relationship to ellipticals. We find that BCGs generally display velocity dispersion profiles with gradients similar to those found in normal bright ellipticals. A rising velocity dispersion profile is found for the BCG IC 1101, the dominant member of Abell 2029, confirming Dressier's (1979) result. No other rising velocity dispersion profiles are found in our sample suggesting that they are not a feature common to brightest duster galaxies. Significant rotation is found in only two of the galaxies, a result in agreement with previous studies showing the declining importance of rotation with increasing luminosity for elliptical galaxies. Our data suggest that environment plays a role in the kinematic characteristics of BCGs. We find a correlation between the rotation of BCGs and the velocity dispersion of their parent clusters in the sense that very slowly rotating galaxies (V-m/(sigma))(not asymptotic to) 650 km s(-1)) clusters. This relation between the internal stellar kinematics of BCGs and the cluster velocity dispersion is in the sense expected if ellipticals formed by merging. Brightest duster galaxy mass-to-light ratios derived from photometric and kinematic modeling are found to be similar to normal elliptical M/L values. For the galaxy NGC 4073, the dominant galaxy in the poor cluster MKW 4, we find that it contains a counterrotating stellar core suggestive of the occurrence of an accretion event(s).
TL;DR: In this article, the authors determined the space density of galaxies as a function of disk central surface brightness and found a distribution which is roughly flat (i.e., approximately equal numbers of galaxies at each surface brightness) faintwards of the Freeman's value.
Abstract: Optical surveys for galaxies are biased against the inclusion of low surface brightness (LSB) galaxies. Disney (1976) suggested that the constancy of disk central surface brightness noticed by Freeman (1970) was not a physical result, but instead was an artifact of sample selection. Since LSB galaxies do exist, the pertinent and still controversial issue is if these newly discovered galaxies constitute a significant percentage of the general galaxy population. In this paper, we address this issue by determining the space density of galaxies as a function of disk central surface brightness. Using the physically reasonable assumption (which is motivated by the data) that central surface brightness is independent of disk scale length, we arrive at a distribution which is roughly flat (i.e. approximately equal numbers of galaxies at each surface brightness) faintwards of the Freeman (1970) value. Brightwards of this, we find a sharp decline in the distribution which is analogous to the turn down in the luminosity function at $L^*$. An intrinsically sharply peaked ``Freeman Law'' distribution can be completely ruled out, and no Gaussian distribution can fit the data. Low surface brightness galaxies (those with central surface brightnesses fainter than $22~B\sb$) comprise $\gtrsim 1/2$ the general galaxy population, so a representative sample of galaxies at $z = 0$ does not really exist at present since past surveys have been insensitive to this component of the general galaxy population.