arXiv subjects

L. Tresse

Publications and source records attributed to L. Tresse.

195 records · Page 11Linked to original sources

arXiv1999

Spectral Analysis of the Stromlo-APM Survey II. Galaxy luminosity function and clustering by spectral type

We study the luminosity function and clustering properties of subsamples of local galaxies selected from the Stromlo-APM survey by the rest-frame equivalent widths of their Halpha and Oii emission lines. The b_J luminosity function of star-forming galaxies has a significantly steeper faint-end slope than that for quiescent galaxies: the majority of sub-L* galaxies are currently undergoing significant star formation. Emission line galaxies are less strongly clustered, both amongst themselves, and with the general galaxy population, than quiescent galaxies. Thus as well as being less luminous, star-forming galaxies also inhabit lower-density regions of the Universe than quiescent galaxies.

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arXiv1999

Spectral Analysis of the Stromlo-APM Survey I. Spectral Properties of Galaxies

We analyze spectral properties of 1671 galaxies from the Stromlo-APM survey, selected to have 15 < b_J < 17.15 and having a mean redshift z = 0.05. This is a representative local sample of field galaxies, so the global properties of the galaxy population provide a comparative point for analysis of more distant surveys. We measure Halpha, Oii 3727, Sii 6716, 6731, Nii 6583 and Oi 6300 equivalent widths and the D_4000 break index. The 5A resolution spectra use an 8 arcsec slit, which typically covers 40-50% of the galaxy area. We find no evidence for systematic trends depending on the fraction of galaxy covered by the slit, and further analysis suggests that our spectra are representative of integrated galaxy spectra. We classify spectra according to their Halpha emission, which is closely related to massive star formation. Overall we find 61% of galaxies are Halpha emitters with rest-frame equivalent widths EW(Halpha) >= 2A. The emission-line galaxy (ELG) fraction is smaller than seen in the CFRS at z = 0.2 and is consistent with a rapid evolution of Halpha luminosity density. The ELG fraction, and EW(Halpha), increase at fainter absolute magnitudes, smaller projected area and smaller D_4000. In the local Universe, faint, small galaxies are dominated by star formation activity, while bright, large galaxies are more quiescent. This picture of the local Universe is quite different from the distant one, where bright galaxies appear to show rapidly-increasing activity back in time. (Abridged)

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arXiv1999

Identification of absorbing galaxies towards the QSO J2233-606 in the Hubble Deep Field South

We present spectroscopic observations of galaxies lying within 1' from the QSO J2233-606 in the HDF-S. Several are found to be coincident in redshift with absorption line systems seen in the HST spectrum of the QSO. We detect a new quasar with z=1.3360 at only 45" angular separation from this QSO. This quasar pair is thus an ideal target for QSO environment studies: indeed, strong HI absorptions are seen at z(abs) = 1.3367 in the QSO spectrum, consistent with neutral hydrogen column densities log N(HI) > 16. A bright galaxy at 4"7 from the QSO is at z = 0.570, corresponding also to HI absorption in the QSO's spectrum. Other galaxies are also discussed.

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arXiv1999

Luminosity Functions and Field Galaxy Population Evolution

Galaxy redshift surveys are outstanding tools for observational cosmology. Mapping the universe as outlined by galaxies leads to fundamental measurements which refine our knowledge of its structure and evolution. Redshift acquisition has undergone tremendous progress thanks to advances in technology, and redshift surveys appear nowadays as routine. Even though they may look simple at face-value, the strategy of a survey and the galaxy-selection criteria have crucial impacts on the interpretation of results. In this lecture, I concentrate on the galaxy luminosity function and its evolution. In particular I consider the luminosity function derived from optically magnitude-selected field galaxy redshift surveys. The aim is to describe the approach to designing state-of-the-art of galaxy surveys and their impact on measurements on luminosity functions. I start by discussing survey strategies, (Section 2). I continue by describing the data required (Section 3), and then review the different estimators to measure luminosity funtions (Section 4). I discuss the luminosity function evolution (Section 5) and I follow by summarizing the status of luminosity measurements (Section 6).

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arXiv1997

HST imaging of CFRS and LDSS galaxies - I: Morphological Properties

(Abridged) We analyse Hubble Space Telescope images of a complete sample of 341 galaxies drawn from both the Canada France and Autofib/Low Dispersion Survey Spectrograph ground-based redshift surveys. We discuss morphological classifications of these galaxies, and quantify possible biases that may arise from various redshift-dependent effects. We then discuss these biases in the context of automated classifications, and quantify the expected misclassification in our system. After allowing for such biases, the redshift distribution for normal spirals, together with their luminosity function derived as a function of redshift, indicates approximately 1 magnitude of luminosity evolution in B(AB) by z=1. The elliptical sample is too small for precise evolutionary constraints. However, we find a substantial increase in the proportion of galaxies with irregular morphology at large redshift. These galaxies also appear to be the dominant cause of the rapid rise with redshift in the blue luminosity density identified in the redshift surveys. Although galaxies with irregular morphology may well comprise a mixture of different physical systems and might not correspond to present day irregulars, it is clear that the apparently declining abundance and luminosities of our distant ``irregulars'' holds an important key to understanding recent evolution in the star formation history of normal galaxies.

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arXiv1997

Hubble Space Telescope imaging of the CFRS and LDSS redshift surveys II: Structural parameter and the evolution of disk galaxies to z=1

(Abridged) Several aspects of the evolution of star-forming galaxies are studied using measures of the 2-dimensional surface brightness profile of a sample of 341 faint objects selected from the CFRS and LDSS redshift surveys that have been observed with the Hubble Space Telescope. The size function of disk scale lengths in disk-dominated galaxies is found to stay roughly constant to z=1. This result, which is strengthened by inclusion of the local de Jong et al (1996) size function, suggests that the scale lengths of typical disks can not have grown substantially with cosmic epoch since z=1, unless a corresponding number of large disks have been destroyed through merging. In addition to a roughly constant number density, the galaxies with large disks have, as a set, properties consistent with the idea that they are similar galaxies observed at different cosmic epochs. However, on average, they show higher B-band disk surface brightnesses, bluer overall (U-V) colors, higher [OII] 3727 equivalent widths and less regular morphologies at high redshift than at low redshift, suggesting an increase in the star-formation rate by a factor of about 3 to z=0.7. This is consistent with the expectations of recent models for the evolution of the disk of the Milky Way and similar galaxies. The evolution of the large disk galaxies is probably not sufficient to account for the evolution of the overall luminosity function of galaxies over the interval 0<z<1, especially if Omega=1. Analysis of the half-light radii of all the galaxies in the sample and construction of the bivariate size-luminosity function suggests that larger changes in the galaxy population are due to smaller galaxies, those with half-light radii around 5 h_{50}^{-1} kpc

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arXiv1996

CFRS XIV: Spectral Properties Of Field Galaxies Up To z = 1

The spectral properties of more than 400 CFRS galaxies and their changes over the redshift interval 0 - 1.3 are investigated. Emission line intensities and equivalent widths for accessible lines have been measured, as well as continuum color indices based on 200A wide spectral regions. Within the CFRS sample, the comoving fraction of galaxies with significant emission lines (EW(OII) > 15A) increases from ~13% locally to over 50% at z > 0.5. The fraction of luminous ( M_{B} < -20) quiescent galaxies (those without [OII] 3727 emission) decreases with redshift from 53% at z = 0.3 to 23% at z > 0.5, the latter fraction being similar to that of early type galaxies at that redshift. There is considerable evidence in the data presented here that star formation increases from z = 0 to z > 0.5 in disk galaxies. However, the absence of extremely blue colors and the presence of significant Balmer absorption suggests that the star formation is primarily taking place over long periods of time, rather than in short-duration, high-amplitude ``bursts''. There are several indications that the average metallicity and dust opacity were lower in emission-line galaxies at high redshift than those typically seen in luminous galaxies locally. Beyond z = 0.7, almost all the emission-line galaxies, including the most luminous (at 1mu at rest) ones, have colors approaching those of present-day irregular galaxies, and a third of them have indications (primarily from the strength of the 4000A break) of metallicities significantly less than solar (Z < 0.2 Z_{sun}). (abbreviated)

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arXiv1996

The Canada-France Redshift Survey XII: Nature of emission-line field galaxy population up to z = 0.3

We present a spectroscopic study of the 138 field galaxies to a redshift z = 0.3 from the I-selected Canada-France Redshift Survey. 117(85%) spectra exhibit at least H alpha in emission, the remaining 21(15%) are purely absorption-line spectra. We focus our analysis on spectra with H alpha and H beta in emission, accounting for about half of this low-z sample, which we classify using emission-line ratio diagrams. Using photoionization models, we determine the extreme boundaries of H II galaxies in these diagnostic diagrams, and demonstrate that the emission-line ratios of a significant fraction of galaxies require harder photoionization sources than massive O stars. We find that about 17% of the field galaxies have emission-line ratios consistent with active galaxies, e.g., Seyfert 2 or LINERs. After correcting for stellar absorption under the Balmer lines, we conclude that the fraction of such galaxies is at least 8% of the field galaxy population at z < 0.3.

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arXiv1995

The Canada France Redshift Survey VIII: Evolution of the clustering of galaxies from z~1

We have used the projected two-point correlation function, $w(r_p)$, to investigate the spatial distribution of the 591 galaxies with secure redshifts between $0 \leq z \leq 1.3$ in the five CFRS fields. The slope of the two-point correlation function for the sample as a whole is $γ=1.64\pm0.05$, very similar to the local slope, and $γ$ is therefore not strongly evolving with redshift. However, the amplitude of the correlation function decreases strongly with increasing redshift, so that at $z\approx0.6$ it is a factor of 10 lower (for $q_0=0.5$) than for a similarly-selected local galaxy population, on scales $0.1<r<2h^{-1}$ Mpc ($q_0=0.5$). As a whole, the CFRS data is adequately represented by $r_0(z=0.53)=1.33 \pm 0.09 h^{-1}$Mpc for $q_0=0.5$, and $r_0(z=0.53)=1.57 \pm 0.09 h^{-1}$Mpc for $q_0=0$. Unless the galaxy population at high redshift is quite different from any population seen locally, an unlikely possibility, then this implies growth of clustering as described by the evolutionary parameter $ε$ to be between $0 < ε< +2$. No difference in the clustering of red and blue galaxies is seen at $z \geq 0.5$, although at lower redshifts, $0.2 \leq z \leq 0.5$, blue galaxies are somewhat less strongly correlated than the redder galaxies, as seen in local samples. This effect could be the equivalent for field galaxies to the Butcher-Oemler effect seen in clusters of galaxies. The cross-correlation functions between red and blue samples have comparable amplitudes to the auto-correlation functions of each. The distribution and power spectrum of pair separations does not indicate

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arXiv1995

The CANADA-FRANCE REDSHIFT SURVEY VI: Evolution of the galaxy luminosity function to z ~ 1

The cosmic evolution of the field galaxy population has been studied out to a redshift of z ~ 1 using a sample of 730 I-band selected galaxies, of which 591 have secure redshifts with median ~ 0.56. The tri-variate luminosity function phi(M,color,z) shows unambiguously that the population evolves and that this evolution is strongly differential with color and, less strongly, with luminosity. The luminosity function of red galaxies shows very little change in either number density or luminosity over the entire redshift range 0 < z < 1. In contrast, the luminosity function of blue galaxies shows substantial evolution at redshifts z > 0.5. By 0.5 < z < 0.75, the blue luminosity function appears to have uniformly brightened by approximately 1 mag. At higher redshifts, the evolution appears to saturate at the brightest magnitudes but continues at fainter levels leading to a steepening of the luminosity function. A significant excess of galaxies relative to the Loveday et al. (1992) local luminosity function is seen at low redshifts z < 0.2 around M(B) ~ -18$ and these galaxies may possibly represent the descendants of the evolving blue population seen at higher redshifts. The changes seen in the luminosity function are also apparent in color-magnitude diagrams constructed at different epochs and in the V/V_max statistic computed as a function of spectral type. Finally, it is argued that the picture of galaxy evolution presented here is consistent with the very much smaller samples of field galaxies that have been selected in other wavebands, and with the results of studies of galaxies selected on the basis of Mg II 2799 absorption.

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arXiv1995

THE CANADA-FRANCE REDSHIFT SURVEY IX: HST Imaging of High-Redshift Field Galaxies

HST B and I images are presented of 32 CFRS galaxies with secure redshifts in the range 0.5 < z < 1.2. These galaxies exhibit the same range of morphological types as seen locally, i.e., ellipticals, spirals and irregulars. The galaxies look far less regular in the $B$ images (rest-frame ultraviolet) than at longer wavelengths, underlining the fact that optical images of galaxies at still higher redshift should be interpreted with caution. Quantitative analyses of the galaxies yield disk sizes, bulge fractions, and colors for each component. At these redshifts, galaxy disks show clear evidence for surface brightness evolution. The mean rest-frame central surface brightness of the disks of normal late-type galaxies is mu_{AB}(B)=20.2 \pm 0.25 mag arcsec^{-2}, about 1.2 mag brighter than the Freeman (1970) value. Some degree of peculiarity is measurable in 10 (30%) of the galaxies and 4 (13%) show clear signs of interaction/mergers. There are 9 galaxies (30%) dominated by blue compact components. These components, which appear to be related to star formation, occur most often in peculiar/asymmetric galaxies (some of which appear to be interacting), but a few are in otherwise normal galaxies. Thus, of the galaxies bluer than present-day Sb, one-third are "blue nucleated galaxies", and half are late-type galaxies with disks which are significantly brighter than normal galaxies at z=0. Taken together, these two effects must be responsible for much of the observed evolution of the luminosity function of blue galaxies.

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arXiv1995

The CANADA-FRANCE REDSHIFT SURVEY I: Introduction to the Survey, Photometric Catalogs and Surface Brightness Selection Effects

The Canada-France Redshift Survey has been undertaken to provide a large well-defined sample of faint galaxies at high redshift in which the selection criteria match as closely as possible those of samples of nearby galaxies. The survey is designed to have a median redshift of z ~ 0.6 corresponding to a look-back time of half the present age of the Universe for Omega ~ 1. Such a survey can then be used for studying many different aspects of the evolution of galaxies over the interval 0 < z < 1. In this paper we describe the selection of the fields, the multicolor imaging observations and the construction and validation of the photometric catalogs. Particular attention is paid to quantifying the unavoidable selection effects in surface brightness and their impact on the survey is assessed in the context of the properties of known populations of galaxies. The photometric catalogs contain several thousand objects brighter than I_{AB}< 22.5 and are essentially complete for central surface brightnesses as faint as $μ_{AB}(I)$ $\sim$ 24.5 mag arcsec$^{-2}$. This should be sufficient to include both normal surface brightness galaxies and prototypes of extreme low surface brightness galaxies.

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arXiv1995

THE CANADA-FRANCE REDSHIFT SURVEY II: Spectroscopic Program; Data for the 0000-00 and 1000+25 Fields

This paper describes the methods used to obtain the spectroscopic data and construct redshift catalogs for the Canada-France deep Redshift Survey (CFRS). The full data set consists of more than one thousand spectra, of objects with 17.5 < I_{AB} < 22.5, obtained from deep multi-slit data with the MARLIN and MOS-SIS spectrographs at the CFHT. The final spectroscopic catalog contains 200 stars, 591 galaxies with secure redshifts in the range 0 < z < 1.3, 6 QSOs, and 146 objects with very uncertain or unknown redshifts, leading to an overall success rate of identification of 85%. Additionally, 67 objects affected by observational problems have been placed in a supplemental list. We describe here the instrumental set up, and the observing procedures used to efficiently gather this large data set. New optimal ways of packing spectra on the detector to significantly increase the multiplexing gain offered by multi-slit spectroscopy are described. Dedicated data reduction procedures have been developed under the IRAF environment to allow for fast and accurate processing. Very strict procedures have been followed to establish a reliable list of final spectroscopic measurements. Fully independent processing of the data has been carried out by three members of the team for each data set associated with a multi-slit mask, and final redshifts were assigned only after the careful comparison of the three independent measurements. A confidence class scheme was established. We strongly emphasize the benefits of such procedures. Finally, we present the spectroscopic data obtained for 303 objects in the 0000-00 and 1000+25 fields. The success rate in spectroscopic identification is

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arXiv1994

Nature of Field Galaxies in the (z<0.3) Universe from the CFRS Survey

We present the first detailed spectroscopic study of field galaxies up to z=0.3 from the I-magnitude limited CFRS sample. In this complete sample, we find that about half of the objects are blue emission-line galaxies. Using line ratio diagram and photoionization models, we show that in roughly half of these emission-line galaxies, ionization by hot stars cannot account for the observed line ratios. Their spectra have properties intermediate between Seyfert 2 galaxies and low-ionization nuclear emission-line regions (LINERs). Their number density (about 20%) relative to the total number of galaxies up to z=0.3, is much larger than the number density (2%) of active galactic nuclei (AGN) in the local Universe. Thus, the observed excess of blue galaxies in counts down to B=24 cannot be mainly due to starburst galaxies, as was previously thought. This result can shed a new light on the nature of the overabundant population of blue galaxies at low redshifts.

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arXiv1994

Surveys for Z>1 Field Galaxies; David Crampton

In the course of the comprehensive CFRS redshift survey to I = 22.5 with the CFHT MOS/SIS spectrograph, we have observed ~25 field galaxies with z > 1. However, it is clear that almost an equal number, predominantly red galaxies, have likely been missed largely because of limitations in the observed wavelength range. The properties of the observed galaxies and the reasons for the presumed incompleteness are briefly discussed in this contribution, and strategies for improving our methods of observing high redshift galaxies are explored. In particular, it is demonstrated that sky subtraction to the required limiting magnitude is possible even with very low spectral resolution, and that new IR arrays and new optical designs for multi-object spectrographs will allow us to easily reach field galaxies at z > 1.

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