Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe Evolution of a Mass-Selected Sample of Early-Type Field Galaxies
91
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We investigate the evolution of mass-selected early-type field galaxies using a sample of 28 gravitational lenses spanning the redshift range 0 < z < 1. Based on the redshift-dependent intercept of the fundamental plane in the rest frame B band, we measure an evolution rate of d log (M/L)_B / dz = -0.56 +/- 0.04 (all errors are 1 sigma unless noted) if we directly compare to the local intercept measured from the Coma cluster. Re-fitting the local intercept helps minimize potential systematic errors, and yields an evolution rate of d log (M/L)_B / dz = -0.54 +/- 0.09. An evolution analysis of properly-corrected aperture mass-to-light ratios (defined by the lensed image separations) is closely related to the Faber-Jackson relation. In rest frame B band we find an evolution rate of d log (M/L)_B / dz = -0.41 +/- 0.21, a present-day characteristic magnitude of M_{*0} = -19.70 + 5 log h +/- 0.29 (assuming a characteristic velocity dispersion of sigma_{DM*} = 225 km/s), and a Faber-Jackson slope of gamma_{FJ} = 3.29 +/- 0.58. The measured evolution rates favor old stellar populations (mean formation redshift z_f > 1.8 at 2 sigma confidence for a Salpeter initial mass function and a flat Omega_m =0.3 cosmology) among early-type field galaxies, and argue against significant episodes of star formation at z < 1.
rate research
Read More
Aims: We present a new method that uses luminosity or stellar mass functions combined with clustering measurements to select samples of galaxies at different redshifts likely to follow a progenitor-to-descendant relationship. As the method uses clustering information, we refer to galaxy samples selected this way as clustering-selected samples. We apply this method to infer the number of mergers during the evolution of MUSYC early-type galaxies (ETGs) from z~1 to the present-day. Methods: The method consists in using clustering information to infer the typical dark-matter halo mass of the hosts of the selected progenitor galaxies. Using LambdaCDM predictions, it is then possible to follow these haloes to a later time where the sample of descendants will be that with the clustering of these descendant haloes. Results: This technique shows that ETGs at a given redshift evolve into brighter galaxies at lower redshifts (considering rest-frame, passively evolved optical luminosities). This indicates that the stellar mass of these galaxies increases with time and that, in principle, a stellar mass selection at different redshifts does not provide samples of galaxies in a progenitor-descendant relationship. Conclusions: The comparison between high redshift ETGs and their likely descendants at z=0 points to a higher number density for the progenitors by a factor 5.5+-4.0, implying the need for mergers to decrease their number density by today. Because the luminosity densities of progenitors and descendants are consistent, our results show no need for significant star-formation in ETGs since z=1, which indicates that the needed mergers are dry, i.e. gas free.
We have measured the Fundamental Plane (FP) parameters for a sample of 30 field early-type galaxies (E/S0) in the redshift range 0.1<z<0.66. We find that: i) the FP is defined and tight out to the highest redshift bin; ii) the intercept gamma evolves as dgamma/dz=0.58+0.09-0.13 (for Omega=0.3, Omega_{Lambda}=0.7), or, in terms of average effective mass to light ratio, as dlog(M/L_B)/dz=-0.72+0.11-0.16, i.e. faster than is observed for cluster E/S0 -0.49+-0.05. In addition, we detect [OII] emission >5AA in 22% of an enlarged sample of 42 massive E/S0 in the range 0.1<z<0.73, in contrast with the quiescent population observed in clusters at similar z. We interpret these findings as evidence that a significant fraction of massive field E/S0 experiences secondary episodes of star-formation at z<1.
(Abridged) We explore the evolution of field early-type galaxies on a sample extracted from GOODS/CDFS. The galaxies are selected by means of a non-parametric analysis followed by visual inspection. We exclude those galaxies which are not consistent with an evolution into the Kormendy relation. The final set comprises 249 galaxies with a median redshift z=0.7. The distribution of number counts versus apparent magnitude suggests a substantial decrease of the comoving number density with redshift. The majority of the galaxies feature passively evolving old stellar populations. One third of those in the upper half of the redshift distribution have blue colors, in contrast to only 10% in the lower redshift subsample. An adaptive binning of the color maps is performed to explore the internal color distribution. We find that most blue galaxies in our sample feature blue cores whereas most of the red early-types are passively evolving stellar populations with red cores. The color gradients and scatter do not evolve with redshift and are compatible with the observations at z=0 assuming a radial dependence of the metallicity within each galaxy. This work emphasizes the need for a careful sample selection, as we found that most of those galaxies which were visually classified as early types -- but then rejected based on the Kormendy relation -- feature blue colors characteristic of recent star formation.
We explore the properties of 24 field early-type galaxies at 0.20<z<0.75 down to M_B<=-19.30 in a sample extracted from the FORS Deep Field and the William Herschel Deep Field. High S/N intermediate-resolution VLT spectroscopy was complemented by deep high-resolution HST/ACS imaging and additional ground-based multi-band photometry. To clarify the low level of star formation (SF) detected in some galaxies, we identify the amount of AGN activity in our sample using archive data of Chandra and XMM-Newton X-ray surveys. The B and K-band Faber-Jackson relations and the Fundamental Plane display a moderate evolution for the field early-type galaxies. Lenticular (S0) galaxies feature on average a stronger luminosity evolution and bluer rest-frame colours which can be explained that they comprise more diverse stellar populations compared to elliptical galaxies. The evolution of the FP can be interpreted as an average change in the dynamical mass-to-light ratio of our galaxies as <Delta log{(M/L_B)}/z>=-0.74pm0.08. The M/L evolution of these field galaxies suggests a continuous mass assembly of field early-type galaxies during the last 5 Gyr, that gets support by recent studies of field galaxies up to z~1. Independent evidence for recent SF activity is provided by spectroscopic (OII em., Hdelta) and photometric (rest-frame colors) diagnostics. Based on the Hdelta absorption feature we detect a weak residual SF for galaxies that accounts for 5%-10% in the total stellar mass of these galaxies. The co-evolution in the luminosity and mass of our galaxies favours a downsizing formation process. We find some evidence that our galaxies experienced a period of SF quenching, possible triggered by AGN activity that is in good agreement with recent results on both observational and theoretical side. (abridged)
We measure the average mass properties of a sample of 41 strong gravitational lenses at moderate redshift (z ~ 0.4 - 0.9), and present the lens redshift for 6 of these galaxies for the first time. Using the techniques of strong and weak gravitational lensing on archival data obtained from the Hubble Space Telescope, we determine that the average mass overdensity profile of the lenses can be fit with a power-law profile (Delta_Sigma prop. to R^{-0.86 +/- 0.16}) that is within 1-sigma of an isothermal profile (Delta_Sigma prop. to R^{-1}) with velocity dispersion sigma_v = 260 +/- 20 km/s. Additionally, we use a two-component de Vaucouleurs+NFW model to disentangle the total mass profile into separate luminous and dark matter components, and determine the relative fraction of each component. We measure the average rest frame V-band stellar mass-to-light ratio (Upsilon_V = 4.0 +/- 0.6 h M_sol/L_sol) and virial mass-to-light ratio (tau_V = 300 +/- 90 h M_sol/L_sol) for our sample, resulting in a virial-to-stellar mass ratio of M_vir/M_* = 75 +/- 25. Finally, we compare our results to a previous study using low redshift lenses, to understand how galaxy mass profiles evolve over time. We investigate the evolution of M_vir/M_*(z) = alpha(1+z)^{beta}, and find best fit parameters of alpha = 51 +/- 36 and beta = 0.9 +/- 1.8, constraining the growth of virial to stellar mass ratio over the last ~7 Gigayears. We note that, by using a sample of strong lenses, we are able to constrain the growth of M_vir/M_*(z) without making any assumptions about the IMF of the stellar population.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
