883 research outputs found
First gravitational lensing mass estimate of a damped Lyman-alpha galaxy at z=2.2
We present the first lensing total mass estimate of a galaxy, at redshift
2.207, that acts as a gravitational deflector and damped Lyman-alpha absorber
on the background QSO SDSS J1135-0010, at redshift 2.888. The remarkably small
projected distance, or impact parameter, between the lens and the source has
been estimated to be 0.8 +/- 0.1 kpc in a recent work. By exploiting the Sloan
Digital Sky Survey database, we establish a likely lensing magnification signal
in the photometry of the QSO. This is determined to be 2.2 mag brighter (or 8
times more luminous) than the median QSO at comparable redshifts. We describe
the total mass distribution of the lens galaxy with a one-component singular
isothermal sphere model and contrast the values of the observed and
model-predicted magnification factors. For the former, we use conservatively
the photometric data of the 95% of the available distant QSO population. We
estimate that the values of the lens effective velocity dispersion and
two-dimensional total mass, projected within a cylinder with radius equal to
the impact parameter, are included between 60 and 170 km/s and 2.1 x 10^9 and
1.8 x 10^10 M_Sun, respectively. We conclude by remarking that analyses of this
kind are crucial to exploring the relation between the luminous and dark matter
components of galaxies in the high-redshift Universe.Comment: 5 pages, 3 figures, accepted by MNRA
The galaxy counterpart of the high-metallicity and 16 kpc impact parameter DLA towards Q0918+1636 - a challenge to galaxy formation models?
The quasar Q0918+1636 (z=3.07) has an intervening high-metallicity Damped
Lyman-alpha Absorber (DLA) along the line of sight, at a redshift of z=2.58.
The DLA is located at a large impact parameter of 16.2 kpc, and has an almost
solar metallicity. It is shown, that a novel type of cosmological galaxy
formation models, invoking a new SNII feedback prescription, the Haardt & Madau
(2012) UVB field and explicit treatment of UVB self-shielding, can reproduce
the observed characteristics of the DLA. UV radiation from young stellar
populations in the galaxy, in particular in the photon energy range 10.36-13.61
eV (relating to Sulfur II abundance), are also considered in the analysis. It
is found that a) for L~L* galaxies (at z=2.58), about 10% of the sight-lines
through the galaxies at impact parameter 16.2 kpc will display a Sulfur II
column density N(SII) 10 cm (the observed value for the
DLA), and b) considering only cases where a near-solar metallicity will be
detected at 16.2 kpc impact parameter, the probability distribution of galaxy
SFR peaks near the value observed for the DLA galaxy counterpart of ~27
Msun/yr. It is argued, that the bulk of the alpha-elements, like Sulfur, traced
by the high metal column density, b=16.2 kpc absorption lines, were produced by
evolving young stars in the inner galaxy, and later transported outward by
galactic winds.Comment: 22 pages, 24 figures, MNRAS in pres
Detecting filaments at z=3
We present the detection of a filament of Ly-alpha emitting galaxies in front
of the quasar Q1205-30 at z=3.04 based on deep narrow band imaging and
follow-up spectroscopy obtained at the ESO NTT and VLT. We argue that Ly-alpha
selection of high redshift galaxies with relatively modest amounts of observing
time allows the detection and redshift measurement of galaxies with
sufficiently high space densities that we can start to map out the large scale
structure at z=2-3 directly. Even more interesting is it that a 3D map of the
filaments will provide a new cosmological test for the value of the
cosmological constant, Omega_Lambda.Comment: 7 pages, 4 figures, contribution to the procedings of the conference
``Lighthouses of the Universe'' held in Garching (Germany), August 200
Verifying the mass-metallicity relation in damped Lyman-alpha selected galaxies at 0.1<z<3.2
A scaling relation has recently been suggested to combine the galaxy
mass-metallicity (MZ) relation with metallicities of damped Lyman-alpha systems
(DLAs) in quasar spectra. Based on this relation the stellar masses of the
absorbing galaxies can be predicted. We test this prediction by measuring the
stellar masses of 12 galaxies in confirmed DLA absorber - galaxy pairs in the
redshift range 0.1<z<3.2. We find an excellent agreement between the predicted
and measured stellar masses over three orders of magnitude, and we determine
the average offset = 0.44+/-0.10 between absorption
and emission metallicities. We further test if could depend on the
impact parameter and find a correlation at the 5.5sigma level. The impact
parameter dependence of the metallicity corresponds to an average metallicity
difference of -0.022+/-0.004 dex/kpc. By including this metallicity vs. impact
parameter correlation in the prescription instead of , the scatter
reduces to 0.39 dex in log M*. We provide a prescription how to calculate the
stellar mass (M*,DLA) of the galaxy when both the DLA metallicity and DLA
galaxy impact parameter is known. We demonstrate that DLA galaxies follow the
MZ relation for luminosity-selected galaxies at z=0.7 and z=2.2 when we include
a correction for the correlation between impact parameter and metallicity.Comment: 15 pages, 6 figures. Major revision. Accepted for publication in
MNRA
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