1,848 research outputs found
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
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
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
The galaxies in the field of the nearby GRB980425/SN1998bw
We present spectroscopic observations of ESO 184-G82, the host galaxy of
GRB980425/SN1998bw, and six galaxies in its field. A host redshift of
z=0.0087+/-0.0006 is derived, consistent with that measured by Tinney et al.
(1998). Redshifts are obtained for the six surrounding galaxies observed. Three
of these galaxies lie within 11 Mpc of each other, confirming the suggestion
that some of these galaxies form a group. However, all of the field galaxies
observed lie at significantly greater distances than ESO 184-G82 and are
therefore not associated with it. The host galaxy of GRB980425/SN1998bw thus
appears to be an isolated dwarf galaxy and interactions with other galaxies do
not seem to be responsible for its star formation.Comment: 5 pages, 2 figures, accepted for publication in A&
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