1,039 research outputs found
Pruning the Lyman alpha forest of Q1331+170
A multitude of absorption lines seen shortward of QSO Ly-alpha emission, that cannot be traced to heavy element absorption systems, are assumed to be Ly-alpha lines arising in intervening clouds. Studies of these Ly-alpha clouds, typically done at 1 A or lower resolution, have shown N(H1) approximately equal to 10(exp 13) - 10(exp 17) sq cm and b approximately equal to 35 km/s. Sargent et al 1980, on the basis of a flat pair velocity correlation function (PVCF), argued that these clouds are intergalactic. But Crotts 1989 showed that the strong Ly-alpha lines are spatially clustered. High resolution studies of Webb 1987 and Rauch et al 1992 also report some evidence for weak clustering, but overall such high resolution studies have been rare. A study of the Ly-alpha forest of Q1331 + 170 over x(sub abs) = 1.60 - 2.19 based on 18 km/s resolution data at S/N approximately equal to 15, with metal-line deblending incorporated
A SINFONI Integral Field Spectroscopy Survey for Galaxy Counterparts to Damped Lyman-alpha Systems - IV. Masses and Gas Flows
The circumgalactic medium (CGM) of typical galaxies is crucial to our
understanding of the cycling of gas into, through and out of galaxies. One way
to probe the CGM is to study gas around galaxies detected via the absorption
lines they produce in the spectra of background quasars. Here, we present
medium resolution and new ~0.4-arcsec resolution (~3 kpc at z~1) 3D
observations with VLT/SINFONI of galaxies responsible for high-N(HI) quasar
absorbers. These data allow to determine in details the kinematics of the
objects: the four z~1 objects are found to be rotation-supported as expected
from inclined discs, while the fifth z~2 system is dispersion-dominated. Two of
the systems show sign of interactions and merging. In addition, we use several
indicators (star formation per unit area, a comparison of emission and
absorption kinematics, arguments based on the inclination and the orientation
of the absorber to the quasar line-of-sight and the distribution of metals) to
determine the direction of the gas flows in and out of these galaxies. In some
cases, our observations are consistent with the gas seen in absorption being
due to material co-rotating with their halos. In the case of absorbing-galaxies
towards Q1009-0026 and Q2222-0946, these indicators point toward the presence
of an outflow traced in absorption.Comment: 18 pages, 11 figures, accepted for publication in MNRA
Diffuse Atomic and Molecular Gas in the Interstellar Medium of M82 toward SN 2014J
We present a comprehensive analysis of interstellar absorption lines seen in
moderately-high resolution, high signal-to-noise ratio optical spectra of SN
2014J in M82. Our observations were acquired over the course of six nights,
covering the period from ~6 days before to ~30 days after the supernova reached
its maximum B-band brightness. We examine complex absorption from Na I, Ca II,
K I, Ca I, CH+, CH, and CN, arising primarily from diffuse gas in the
interstellar medium (ISM) of M82. We detect Li I absorption over a range in
velocity consistent with that exhibited by the strongest Na I and K I
components associated with M82; this is the first detection of interstellar Li
in a galaxy outside of the Local Group. There are no significant temporal
variations in the absorption-line profiles over the 37 days sampled by our
observations. The relative abundances of the various interstellar species
detected reveal that the ISM of M82 probed by SN 2014J consists of a mixture of
diffuse atomic and molecular clouds characterized by a wide range of
physical/environmental conditions. Decreasing N(Na I)/N(Ca II) ratios and
increasing N(Ca I)/N(K I) ratios with increasing velocity are indicative of
reduced depletion in the higher-velocity material. Significant
component-to-component scatter in the N(Na I)/N(Ca II) and N(Ca I)/N(Ca II)
ratios may be due to variations in the local ionization conditions. An apparent
anti-correlation between the N(CH+)/N(CH) and N(Ca I)/N(Ca II) ratios can be
understood in terms of an opposite dependence on gas density and radiation
field strength, while the overall high CH+ abundance may be indicative of
enhanced turbulence in the ISM of M82. The Li abundance also seems to be
enhanced in M82, which supports the conclusions of recent gamma-ray emission
studies that the cosmic-ray acceleration processes are greatly enhanced in this
starburst galaxy.Comment: 32 pages, 6 figures, accepted to ApJ; added table giving single-epoch
equivalent widths; improved discussion regarding the lack of temporal
variations; improved analysis of the Li I regio
The Composite Spectrum of Strong Lyman-alpha Forest Absorbers
We present a new method for probing the physical conditions and metal
enrichment of the Intergalactic Medium: the composite spectrum of Ly-alpha
forest absorbers. We apply this technique to a sample of 9480 Ly-alpha
absorbers with redshift 2 < z < 3.5 identified in the spectra of 13,279
high-redshift quasars from the Sloan Digital Sky Survey (SDSS) Fifth Data
Release (DR5). Absorbers are selected as local minima in the spectra with 2.4 <
tau_Ly-alpha < 4.0; at SDSS resolution (~ 150km/s FWHM), these absorbers are
blends of systems that are individually weaker. In the stacked spectra we
detect seven Lyman-series lines and metal lines of O VI, N V, C IV, C III, Si
IV, C II, Al II, Si II, Fe II, Mg II, and O I. Many of these lines have peak
optical depths of < 0.02, but they are nonetheless detected at high statistical
significance. Modeling the Lyman-series measurements implies that our selected
systems have total H I column densities N_HI ~ 10^15.4cm-2. Assuming typical
physical conditions rho / = 10, T = 10^4 - 10^4.5 K, and [Fe/H]= -2
yields reasonable agreement with the line strengths of high-ionization species,
but it underpredicts the low-ionization species by two orders of magnitude or
more. This discrepancy suggests that the low ionization lines arise in dense,
cool, metal-rich clumps, present in some absorption systems.Comment: 7 pages, 4 figures, 1 table, accepted by ApJL, revisions mad
Keck and VLT Observations of Super-damped Lyman-alpha Absorbers at z=2=2.5: Constraints on Chemical Compositions and Physical Conditions
We report Keck/ESI and VLT/UVES observations of three super-damped
Lyman-alpha quasar absorbers with H I column densities log N(HI) >= 21.7 at
redshifts z=2-2.5. All three absorbers show similar metallicities (-1.3 to -1.5
dex), and dust depletion of Fe, Ni, and Mn. Two of the absorbers show
supersolar [S/Zn] and [Si/Zn]. We combine our results with those for other DLAs
to examine trends between N(HI), metallicity, dust depletion. A larger fraction
of the super-DLAs lie close to or above the line [X/H]=20.59-log N(HI) in the
metallicity vs. N(HI) plot, compared to the less gas-rich DLAs, suggesting that
super-DLAs are more likely to be rich in molecules. Unfortunately, our data for
Q0230-0334 and Q0743+1421 do not cover H2 absorption lines. For Q1418+0718,
some H2 lines are covered, but not detected. CO is not detected in any of our
absorbers. For DLAs with log N(HI) < 21.7, we confirm strong correlation
between metallicity and Fe depletion, and find a correlation between
metallicity and Si depletion. For super-DLAs, these correlations are weaker or
absent. The absorbers toward Q0230-0334 and Q1418+0718 show potential
detections of weak Ly-alpha emission, implying star formation rates of about
1.6 and 0.7 solar masses per year, respectively (ignoring dust extinction).
Upper limits on the electron densities from C II*/C II or Si II*/Si II are low,
but are higher than the median values in less gas-rich DLAs. Finally, systems
with log N(HI) > 21.7 may have somewhat narrower velocity dispersions delta
v_90 than the less gas-rich DLAs, and may arise in cooler and/or less turbulent
gas.Comment: 57 pages, 15 figures. Accepted for publication in Ap
Do broad absorption line quasars live in different environments from ordinary quasars?
We select a sample of traditionally defined broad absorption line
quasars (BALQs) from the Fifth Data Release quasar catalog of the Sloan Digital
Sky Survey. For a statistically homogeneous quasar sample with , the BAL quasar fraction is and is almost constant with
redshift. We measure the auto-correlation of non-BAL quasars (nonBALQs) and the
cross-correlation of BALQs with nonBALQs using this statistically homogeneous
sample, both in redshift space and using the projected correlation function. We
find no significant difference between the clustering strengths of BALQs and
nonBALQs. Assuming a power-law model for the real space correlation function
, the correlation length for nonBALQs is ; for BALQs, the cross-correlation length is . Our clustering results suggest that BALQs live in similar
large-scale environments as do nonBALQs.Comment: accepted for publication in Ap
The Cross-correlation of MgII Absorption and Galaxies in BOSS
We present a measurement of the cross-correlation of MgII absorption and
massive galaxies, using the DR11 main galaxy sample of the Baryon Oscillation
Spectroscopic Survey of SDSS-III (CMASS galaxies), and the DR7 quasar spectra
of SDSS-II. The cross-correlation is measured by stacking quasar absorption
spectra shifted to the redshift of galaxies that are within a certain impact
parameter bin of the quasar, after dividing by a quasar continuum model. This
results in an average MgII equivalent width as a function of impact parameter
from a galaxy, ranging from 50 kpc to more than 10 Mpc in proper units, which
includes all MgII absorbers. We show that special care needs to be taken to use
an unbiased quasar continuum estimator, to avoid systematic errors in the
measurement of the mean stacked MgII equivalent width. The measured
cross-correlation follows the expected shape of the galaxy correlation
function, although measurement errors are large. We use the cross-correlation
amplitude to derive the bias factor of MgII absorbers, finding bMgII = 2.33
\pm? 0.19, where the error accounts only for the statistical uncertainty in
measuring the mean equivalent width. This bias factor is larger than that
obtained in previous studies and may be affected by modeling uncertainties that
we discuss, but if correct it suggests that MgII absorbers at redshift z \simeq
0:5 are spatially distributed on large scales similarly to the CMASS galaxies
in BOSS.
Keywords: galaxies: haloes, galaxies: formation, quasars: absorption lines,
large-scale structure of universeComment: Accepted for publication to MNRAS. Accepted 2014 December 12.
Received 2014 November 29; in original form 2014 February
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