52 research outputs found
Properties of Faint Distant Galaxies as seen through Gravitational Telescopes
This paper reviews the most recent developments related to the use of lensing
clusters of galaxies as Gravitational Telescopes in deep Universe studies. We
summarize the state of the art and the most recent results aiming at studying
the physical properties of distant galaxies beyond the limits of conventional
spectroscopy. The application of photometric redshift techniques in the context
of gravitational lensing is emphasized for the study of both lensing structures
and the background population of lensed galaxies. A presently ongoing search
for the first building blocks of galaxies behind lensing clusters is presented
and discussed.Comment: Review lecture given at "Gravitational Lensing: a unique tool for
cosmology",Aussois, France, January 2003. To appear in ASP Conf. S., eds. D.
Valls-Gabaud & J.-P. Kneib, 26 pages, 8 figure
2D Kinematics and Physical Properties of z~3 Star-Forming Galaxies
We present results from a study of the kinematic structure of star-forming
galaxies at redshift z~3 selected in the VVDS, using integral-field
spectroscopy of rest-frame optical nebular emission lines, in combination with
rest-frame UV spectroscopy, ground-based optical/near-IR and Spitzer
photometry. We also constrain the underlying stellar populations to address the
evolutionary status of these galaxies. We infer the kinematic properties of
four galaxies: VVDS-20298666, VVDS-020297772, VVDS-20463884 and VVDS-20335183
with redshifts z = 3.2917, 3.2878, 3.2776, and 3.7062, respectively. While
VVDS-20463884 presents an irregular velocity field with a peak in the local
velocity dispersion of the galaxy shifted from the centre of the galaxy,
VVDS-20298666 has a well-resolved gradient in velocity over a distance of ~4.5
kpc with a peak-to-peak amplitude of v = 91 km/s . We discovered that the
nearby galaxy, VVDS-020297772 (which shows traces of AGN activity), is in fact
a companion at a similar redshift with a projected separated of 12 kpc. In
contrast, the velocity field of VVDS-020335183 seems more consistent with a
merger on a rotating disk. However, all of the objects have a high local
velocity dispersion (sigma ~ 60-70 km/s), which gives v/sigma < 1. It is
unlikely that these galaxies are dynamically cold rotating disk of ionized gas.Comment: 14 pages and 16 figure
Studying the kinematic asymmetries of disks and post-coalescence mergers using a new `kinemetry' criterion
We have obtained VIMOS/VLT optical integral field spectroscopy (IFS) data for
a sample of 4 LIRGs which have been selected at a similar distance ( 70
Mpc) to avoid relative resolution effects. They have been classified in two
groups (isolated disk and post-coalescence mergers) according to their
morphology. The method (developed by Krajnovic and coworkers) is
used to characterize the kinematic properties of these galaxies and to discuss
new criteria for distinguishing their status. We present and discuss new
kinematic maps (i.e., velocity field and velocity dispersion) for these four
galaxies. The morphological and kinematic classifications of these systems are
consistent, with disks having lower kinematic asymmetries than post-coalescence
mergers. We then propose and discuss a new kinematic criterion to differentiate
these two groups. This criterion distinguishes better these two categories and
has the advantage of being less sensitive to angular resolution effects.
According to the previous criteria,the present post-coalescence systems would
have been classified as disks. This indicates that the separation of disks from
mergers is subjective to the definition of `merger'. It also suggests that
previous estimates of the merger/disk ratio could have been underestimated, but
larger samples are necessary to establish a firmer conclusion.Comment: 15 figures, 19 page
Integral field spectroscopy with SINFONI of VVDS galaxies. II. The mass-metallicity relation at 1.2 < z < 1.6
This work aims to provide a first insight into the mass-metallicity (MZ)
relation of star-forming galaxies at redshift z~1.4. To reach this goal, we
present a first set of nine VVDS galaxies observed with the NIR integral-field
spectrograph SINFONI on the VLT. Oxygen abundances are derived from empirical
indicators based on the ratio between strong nebular emission-lines (Halpha,
[NII]6584 and [SII]6717,6731). Stellar masses are deduced from SED fitting with
Charlot & Bruzual (2007) population synthesis models, and star formation rates
are derived from [OII]3727 and Halpha emission-line luminosities. We find a
typical shift of 0.2-0.4 dex towards lower metallicities for the z~1.4
galaxies, compared to the MZ-relation in the local universe as derived from
SDSS data. However, this small sample of eight galaxies does not show any clear
correlation between stellar mass and metallicity, unlike other larger samples
at different redshift (z~0, z~0.7, and z~2). Indeed, our galaxies lie just
under the relation at z~2 and show a small trend for more massive galaxies to
be more metallic (~0.1 logarithmic slope). There are two possible explanations
to account for these observations. First, the most massive galaxies present
higher specific star formation rates when compared to the global VVDS sample
which could explain the particularly low metallicity of these galaxies as
already shown in the SDSS sample. Second, inflow of metal-poor gas due to tidal
interactions could also explain the low metallicity of these galaxies as two of
these three galaxies show clear signatures of merging in their velocity fields.
Finally, we find that the metallicity of 4 galaxies is lower by ~0.2 to 0.4 dex
if we take into account the N/O abundance ratio in their metallicity estimate.Comment: 7 pages, 4 figures, accepted in A&A Comments: Comments: more accurate
results with better stellar mass estimate
A SINFONI Integral Field Spectroscopy Survey for Galaxy Counterparts to Damped Lyman-alpha Systems - II. Dynamical Properties of the Galaxies towards Q0302-223 and Q1009-0026
Details of processes through which galaxies convert their gas into stars need
to be studied in order to obtain a complete picture of galaxy formation. One
way to tackle these phenomena is to relate the HI gas and the stars in
galaxies. Here, we present dynamical properties of Damped and sub-Damped
Lyman-alpha Systems identified in H-alpha emission with VLT/SINFONI at near
infra-red wavelengths. While the DLA towards Q0302-223 is found to be
dispersion-dominated, the sub-DLA towards Q1009-0026 shows clear signatures of
rotation. We use a proxy to circular velocity to estimate the mass of the halo
in which the sub-DLA resides and find M_halo=10^12.6 M_sun. We also derive
dynamical masses of these objects, and find M_dyn=10^10.3 M_sun and 10^10.9
M_sun. For one of the two systems (towards Q0302-223), we are able to derive a
stellar mass of M_*=10^9.5 M_sun from Spectral Energy Distribution fit. The gas
fraction in this object is 1/3rd, comparable to similar objects at these
redshifts. Our work illustrates that detailed studies of quasar absorbers can
offer entirely new insights into our knowledge of the interaction between stars
and the interstellar gas in galaxies.Comment: 6 pages, 2 figures. Accepted for publication in MNRA
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