225 research outputs found
Mg II Absorption Characteristics of a Volume-Limited Sample of Galaxies at z ~ 0.1
We present an initial survey of Mg II absorption characteristics in the halos
of a carefully constructed, volume-limited subsample of galaxies embedded in
the spectroscopic part of the Sloan Digital Sky Survey. We observed quasars
near sightlines to 20 low-redshift (z ~ 0.1), luminous M_r <= -20.5 galaxies in
SDSS DR4 and DR6 with the LRIS-B spectrograph on the Keck I telescope. The
primary systematic criteria for the targeted galaxies are a redshift z >~ 0.1
and the presence of an appropriate bright background quasar within a projected
75 kpc/h of its center, although we preferentially sample galaxies with lower
impact parameters and slightly more star formation within this range. Of the
observed systems, six exhibit strong [EW(2796) >= 0.3 Ang.] Mg II absorption at
the galaxy's redshift, six systems have upper limits which preclude strong Mg
II absorption, while the remaining observations rule out very strong [EW(2796)
>= 1-2 Ang] absorption. The absorbers fall at higher impact parameters than
many non-absorber sightlines, indicating a covering fraction f_c =
0.3-Angstrom absorbers at z ~ 0.1, even at impact parameters <= 35 kpc/h (f_c ~
0.25). The data are consistent with a possible dependence of covering fraction
and/or absorption halo size on the environment or star-forming properties of
the central galaxy.Comment: accepted for publication in A
The WHIQII Survey: Metallicities and Spectroscopic Properties of Luminous Compact Blue Galaxies
As part of the WIYN High Image Quality Indiana Irvine (WHIQII) survey, we
present 123 spectra of emission-line galaxies, selected on intermediate
redshift (.4<z<.8) galaxies with blue colors that appear physically compact.
The sample includes 15 true Luminous Compact Blue Galaxies (LCBGs) and an
additional 27 slightly less extreme emission-line systems. These galaxies
represent a highly evolving class that may play an important role in the
decline of star formation since z~1, but their exact nature and evolutionary
pathways remain a mystery. Here, we use emission lines to determine
metallicities and ionization parameters, constraining their intrinsic
properties and state of star formation. Some LCBG metallicities are consistent
with a "bursting dwarf" scenario, while a substantial fraction of others are
not, further confirming that LCBGs are a highly heterogeneous population but
are broadly consistent with the intermediate redshift field. In agreement with
previous studies, we observe overall evolution in the luminosity-metallicity
relation at intermediate redshift. Our sample, and particularly the LCBGs,
occupy a region in the empirical R23-O32 plane that differs from luminous local
galaxies and is more consistent with dwarf Irregulars at the present epoch,
suggesting that cosmic "downsizing" is observable in even the most fundamental
parameters that describe star formation. These properties for our sample are
also generally consistent with lying between local galaxies and those at high
redshift, as expected by this scenario. Surprisingly, our sample exhibits no
detectable correlation between compactness and metallicity, strongly suggesting
that at these epochs of rapid star formation, the morphology of compact
star-forming galaxies is largely transient.Comment: ApJ accepted, 17 pages, 20 figures, 2 tables (complete tables in
published version
A UV-visible prime focus camera for the Keck telescopes
Many areas of astronomical research rely on deep blue wide-field imaging. Mauna Kea enjoys the very best UV transparency from the ground and the Keck telescopes with 10 meter f/1.75 primaries are well suited to a prime focus camera with a large angular field. Swinburne University leads a proposal to provide a camera (KWFI, for Keck Wide Field Imager) that is optimized in the UV but works well to 1μm wavelength. Keck has interchangeable top end modules, of which one is now unused and easily capable of housing the required corrector lens and detector enclosure. This paper concentrates on details of the KWFI optical design
The restframe ultraviolet of superluminous supernovae -- I. Potential as cosmological probes
Superluminous supernovae (SLSNe) have been detected to and can be
detected to using current and upcoming facilities. SLSNe are
extremely UV luminous, and hence objects at are detected
exclusively via their rest-frame UV using optical and infrared facilities.
SLSNe have great utility in multiple areas of stellar and galactic evolution.
Here, we explore the potential use of SLSNe type-I as high-redshift
cosmological distance indicators in their rest-frame UV. Using a SLSNe-I sample
in the redshift range , we investigate correlations
between the peak absolute magnitude in a synthetic UV filter centered at 250 nm
and rise time, colour and decline rate of SLSNe-I light curves. We observe a
linear correlation between and the rise time with an intrinsic
scatter of 0.29. Interestingly, this correlation is further tightened
() by eliminating those SLSNe which show a pre-peak
bump in their light curve. This result hints at the possibility that the
"bumpy" SLSNe could belong to a different population. Weak correlations are
observed between the peak luminosity and colour indices. No relationship is
found between UV peak magnitude and the decline rate in contrast to what is
typically found in optical band. The correlations found here are promising, and
give encouraging insights for the use of SLSNe as cosmological probes at high
redshifts using standardising relations in the UV. We also highlight the
importance of early, and consistent, photometric data for constraining the
light curve properties.Comment: Accepted for publication in MNRA
Measurement of the Spatial Cross-Correlation Function of Damped Lyman Alpha Systems and Lyman Break Galaxies
We present the first spectroscopic measurement of the spatial
cross-correlation function between damped Lyman alpha systems (DLAs) and Lyman
break galaxies (LBGs). We obtained deep u'BVRI images of nine QSO fields with
11 known z ~ 3 DLAs and spectroscopically confirmed 211 R < 25.5
photometrically selected z > 2 LBGs. We find strong evidence for an overdensity
of LBGs near DLAs versus random, the results of which are similar to that of
LBGs near other LBGs. A maximum likelihood cross-correlation analysis found the
best fit correlation length value of r_0 = 2.9^(+1.4)_(-1.5) h^(-1)Mpc using a
fixed value of gamma = 1.6. The implications of the DLA-LBG clustering
amplitude on the average dark matter halo mass of DLAs are discussed.Comment: 12 pages, 2 figures, accepted for publication in Astrophysical
Journal Letter
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