27 research outputs found
The extent of chemically enriched gas around star-forming dwarf galaxies
Supernova driven winds are often invoked to remove chemically enriched gas
from dwarf galaxies to match their low observed metallicities. In such shallow
potential wells, outflows may produce massive amounts of enriched halo gas
(circum-galactic medium or CGM) and pollute the intergalactic medium (IGM).
Here, we present a survey of the CGM and IGM around 18 star-forming field
dwarfs with stellar masses of at .
Eight of these have CGM probed by quasar absorption spectra at projected
distances, , less than the host virial radius, . Ten are probed
in the surrounding IGM at . The absorption measurements
include neutral hydrogen, the dominant silicon ions for diffuse cool gas
( K; Si II, Si III, and Si IV), moderately ionized carbon (C IV),
and highly ionized oxygen (O VI). Metal absorption from the CGM of the dwarfs
is less common and weaker compared to massive star-forming
galaxies though O VI absorption is still common. None of the dwarfs probed at
have definitive metal-line detections. Combining the
available silicon ions, we estimate that the cool CGM of the dwarfs accounts
for only of the expected silicon budget from the yields of supernovae
associated with past star-formation. The highly ionized O VI accounts for
of the oxygen budget. As O VI traces an ion with expected
equilibrium ion fractions of , the highly ionized CGM may
represent a significant metal reservoir even for dwarfs not expected to
maintain gravitationally shock heated hot halos.Comment: Accepted to ApJL, 10 pages, 3 figures, 2 tables. Please contact the
corresponding author for additional column density measurements if needed. v3
includes additional references and clarification in the introductio
Magellan LDSS3 emission confirmation of galaxies hosting metal-rich Lyman-alpha absorption systems
Using the Low Dispersion Survey Spectrograph 3 at the Magellan II Clay
Telescope, we target {candidate absorption host galaxies} detected in deep
optical imaging {(reaching limiting apparent magnitudes of 23.0-26.5 in and filters) in the fields of three QSOs, each of which shows the
presence of high metallicity, high absorption systems in their
spectra (Q0826-2230: =0.9110, Q1323-0021: ,
Q1436-0051: ). We confirm three host galaxies {at
redshifts 0.7387, 0.7401, and 0.9286} for two of the Lyman- absorption
systems (one with two galaxies interacting). For these systems, we are able to
determine the star formation rates (SFRs); impact parameters (from previous
imaging detections); the velocity shift between the absorption and emission
redshifts; and, for one system, also the emission metallicity.} Based on
previous photometry, we find these galaxies have LL. The [O II]
SFRs for these galaxies are in the range M yr
{(uncorrected for dust)}, while the impact parameters lie in the range
kpc. {Despite the fact that we have confirmed galaxies at 50 kpc from the QSO,
no gradient in metallicity is indicated between the absorption metallicity
along the QSO line of sight and the emission line metallicity in the galaxies.}
We confirm the anti-correlation between impact parameter and from
the literature. We also report the emission redshift of five other galaxies:
three at , and two (LL) at not
corresponding to any known absorption systems.Comment: 14 pages, 7 figures, 4 tables, accepted to MNRA
A SINFONI Integral Field Spectroscopy Survey for Galaxy Counterparts to Damped Lyman-alpha Systems - VI. Metallicity and Geometry as Gas Flow Probes
The use of background quasars provides a powerful tool to probe the cool gas
in the circum-galactic medium of foreground galaxies. Here, we present new
observations with SINFONI and X-Shooter of absorbing-galaxy candidates at
z=0.7-1. We report the detection with both instruments of the H-alpha emission
line of one sub-DLA at z_abs=0.94187 with log N(HI)=19.38^+0.10_-0.15 towards
SDSS J002133.27+004300.9. We estimate the star formation rate: SFR=3.6+/-2.2
solar masses per year in that system. A detailed kinematic study indicates a
dynamical mass M_dyn=10^9.9+/-0.4 solar masses and a halo mass
M_halo=10^11.9+/-0.5 solar masses. In addition, we report the OII detection
with X-Shooter of another DLA at z_abs=0.7402 with log N(HI)=20.4+/-0.1 toward
Q0052+0041 and an estimated SFR of 5.3+/-0.7 solar masses per year. Three other
objects are detected in the continuum with X-Shooter but the nature and
redshift of two of these objects are unconstrained due to the absence of
emission lines, while the third object might be at the redshift of the quasar.
We use the objects detected in our whole N(HI)-selected SINFONI survey to
compute the metallicity difference between the galaxy and the absorbing gas,
delta_HI(X), where a positive (negative) value indicates infall (outflow). We
compare this quantity with the quasar line of sight alignment with the galaxy's
major (minor) axis, another tracer of infall (outflow). We find that these
quantities do not correlate as expected from simple assumptions. Additional
observations are necessary to relate these two independent probes of gas flows
around galaxies.Comment: 16 pages, 8 figures, accepted for publication in MNRA
Damped Ly-alpha Absorbers in Star-forming Galaxies at z < 0.15 Detected with the Hubble Space Telescope and Implications for Galaxy Evolution
We report {\it HST} COS spectroscopy of 10 quasars with foreground
star-forming galaxies at 0.02 0.14 within impact parameters of
1-7 kpc. We detect damped/sub-damped Ly absorption in 100 of
cases where no higher-redshift Lyman-limit systems extinguish the flux at the
expected wavelength of Ly absorption, obtaining the largest targeted
sample of DLA/sub-DLAs in low-redshift galaxies. We present absorption
measurements of neutral hydrogen and metals. Additionally, we present GBT 21-cm
emission measurements for 5 of the galaxies (including 2 detections). Combining
our sample with the literature, we construct a sample of 115 galaxies
associated with DLA/sub-DLAs spanning 04.4, and examine trends between
gas and stellar properties, and with redshift. The H~I column density is
anti-correlated with impact parameter and stellar mass. More massive galaxies
appear to have gas-rich regions out to larger distances. The specific SFR
(sSFR) of absorbing galaxies increases with redshift and decreases with
, consistent with evolution of the star-formation main sequence
(SFMS). However, 20 of absorbing galaxies lie below the SFMS,
indicating that some DLA/sub-DLAs trace galaxies with longer-than-typical
gas-depletion time-scales. Most DLA/sub-DLA galaxies with 21-cm emission have
higher H I masses than typical galaxies with comparable . High
ratios and high sSFRs in DLA/sub-DLA galaxies with
suggest these galaxies may be gas-rich because
of recent gas accretion rather than inefficient star formation. Our study
demonstrates the power of absorption and emission studies of DLA/sub-DLA
galaxies for extending galaxy-evolution studies to previously under-explored
regimes of low and low SFR.Comment: 51 pages, 12 figures. Submitted to the Astrophysical Journa
Galactic nebular lines in the fiber spectra of background QSOs: Reaching a hundred QSO-galaxy pairs with spectroscopic and photometric measurements
We present photometric and spectroscopic measurements of 53 QSO-galaxy pairs
from the Sloan Digital Sky Survey, where nebular emission lines from a 0<z<0.84
foreground galaxy are detected in the fiber spectra of a background QSO,
bringing the overall sample to 103 QSO-galaxy pairs detected in the SDSS. We
here study the nature of these systems. Detected foreground galaxies appear at
impact parameters between 0.37 kpc and 12.68 kpc. The presence of oxygen and
Balmer emission lines allows us to determine the emission line metallicities
for our sample, which are on average super-solar in value. Star formation rates
for our sample are in the range 0.01-12 M_sol yr^-1. We utilize photometric
redshift fitting techniques to estimate the M_stellar values of our galaxies
(log M_stellar = 7.34 - 11.54), and extrapolate this relationship to those
galaxies with no imaging detections. Where available, we measure the absorption
features present in the QSO spectrum due to the foreground galaxy and the
relationships between their rest equivalent widths. We report an
anti-correlation between impact parameter and E(B-V)_(g-i), as well as a
correlation between galaxy color (u-r) and E(B-V)_(g-i). We find that our
sample is one of late-type, star forming galaxies comparable to field galaxies
in a similar redshift range, providing important clues to better understand
absorption systems. These galaxies represent a sample of typical galaxies in
the local Universe for which abundances, extinction, morphology, and absorption
properties may be measured using background QSOs with great potential for
follow-up observations.Comment: 31 pages, 10 figures, 6 tables, MNRAS accepte
MusE GAs FLOw and Wind (MEGAFLOW) I: First MUSE results on background quasars
The physical properties of galactic winds are one of the keys to understand
galaxy formation and evolution. These properties can be constrained thanks to
background quasar lines of sight (LOS) passing near star-forming galaxies
(SFGs). We present the first results of the MusE GAs FLOw and Wind (MEGAFLOW)
survey obtained of 2 quasar fields which have 8 MgII absorbers of which 3 have
rest-equivalent width greater than 0.8 \AA. With the new Multi Unit
Spectroscopic Explorer (MUSE) spectrograph on the Very Large Telescope (VLT),
we detect 6 (75) MgII host galaxy candidates withing a radius of 30 arcsec
from the quasar LOS. Out of these 6 galaxy--quasar pairs, from geometrical
arguments, one is likely probing galactic outflows, two are classified as
"ambiguous", two are likely probing extended gaseous disks and one pair seems
to be a merger. We focus on the windpair and constrain the outflow using a
high resolution quasar spectra from Ultraviolet and Visual Echelle Spectrograph
(UVES). Assuming the metal absorption to be due to gas flowing out of the
detected galaxy through a cone along the minor axis, we find outflow velocities
of the order of 150 km/s (i.e. smaller than the escape velocity) with
a loading factor, SFR, of 0.7. We see
evidence for an open conical flow, with a low-density inner core. In the
future, MUSE will provide us with about 80 multiple galaxyquasar pairs in
two dozen fields.Comment: 20 pages, 16 figures, accepted for publication in Ap
Ubiquitous giant Ly nebulae around the brightest quasars at revealed with MUSE
Direct Ly imaging of intergalactic gas at has recently
revealed giant cosmological structures around quasars, e.g. the Slug Nebula
(Cantalupo et al. 2014). Despite their high luminosity, the detection rate of
such systems in narrow-band and spectroscopic surveys is less than 10%,
possibly encoding crucial information on the distribution of gas around quasars
and the quasar emission properties. In this study, we use the MUSE
integral-field instrument to perform a blind survey for giant Ly
nebulae around 17 bright radio-quiet quasars at that does not suffer
from most of the limitations of previous surveys. After data reduction and
analysis performed with specifically developed tools, we found that each quasar
is surrounded by giant Ly nebulae with projected sizes larger than 100
physical kpc and, in some cases, extending up to 320 kpc. The circularly
averaged surface brightness profiles of the nebulae appear very similar to each
other despite their different morphologies and are consistent with power laws
with slopes . The similarity between the properties of all these
nebulae and the Slug Nebula suggests a similar origin for all systems and that
a large fraction of gas around bright quasars could be in a relatively "cold"
(T10K) and dense phase. In addition, our results imply that such gas
is ubiquitous within at least 50 kpc from bright quasars at
independently of the quasar emission opening angle, or extending up to 200 kpc
for quasar isotropic emission.Comment: 19 pages, 9 figures, 3 Tables, accepted to Ap
The Geometry of Cold, Metal-Enriched Gas Around Galaxies at
We present the first results from a Hubble Space Telescope WFC3/IR program,
which obtained direct imaging and grism observations of galaxies near quasar
sightlines with a high frequency of uncorrelated foreground Mg II absorption.
These highly efficient observations targeted 54 Mg II absorbers along the line
of sight to nine quasars at . We find that 89% of the absorbers
in the range can be spectroscopically matched to at least one
galaxy with an impact parameter less than 200 kpc and .
We have estimated the star formation rates and measured structural parameters
for all detected galaxies with impact parameters in the range 7-200 kpc and
star formation rates greater than 1.3 M yr. We find that
galaxies associated with Mg II absorption have significantly higher mean star
formation rates and marginally higher mean star formation rate surface
densities compared to galaxies with no detected Mg II. Nearly half of the Mg II
absorbers match to more than one galaxy, and the mean equivalent width of the
Mg II absorption is found to be greater for groups, compared to isolated
galaxies. Additionally, we observe a significant redshift evolution in the
physical extent of Mg II-absorbing gas around galaxies and evidence of an
enhancement of Mg II within 50 degrees of the minor axis, characteristic of
outflows, which persists to 80 kpc around the galaxies, in agreement with
recent predictions from simulations.Comment: 21 pages, 20 figures, Submitted to Ap
On the Kinematics of Cold, Metal-enriched Galactic Fountain Flows in Nearby Star-forming Galaxies
We use medium-resolution Keck/Echellette Spectrograph and Imager spectroscopy
of bright quasars to study cool gas traced by CaII 3934,3969 and NaI 5891,5897
absorption in the interstellar/circumgalactic media of 21 foreground
star-forming galaxies at redshifts 0.03 < z < 0.20 with stellar masses 7.4 <
log M_*/M_sun < 10.6. The quasar-galaxy pairs were drawn from a unique sample
of Sloan Digital Sky Survey quasar spectra with intervening nebular emission,
and thus have exceptionally close impact parameters (R_perp < 13 kpc). The
strength of this line emission implies that the galaxies' star formation rates
(SFRs) span a broad range, with several lying well above the star-forming
sequence. We use Voigt profile modeling to derive column densities and
component velocities for each absorber, finding that column densities N(CaII) >
10^12.5 cm^-2 (N(NaI) > 10^12.0 cm^-2) occur with an incidence f_C(CaII) =
0.63^+0.10_-0.11 (f_C(NaI) = 0.57^+0.10_-0.11). We find no evidence for a
dependence of f_C or the rest-frame equivalent widths W_r(CaII K) or W_r(NaI
5891) on R_perp or M_*. Instead, W_r(CaII K) is correlated with local SFR at
>3sigma significance, suggesting that CaII traces star formation-driven
outflows. While most of the absorbers have velocities within +/-50 km/s of the
host redshift, their velocity widths (characterized by Delta v_90) are
universally 30-177 km/s larger than that implied by tilted-ring modeling of the
velocities of interstellar material. These kinematics must trace galactic
fountain flows and demonstrate that they persist at R_perp > 5 kpc. Finally, we
assess the relationship between dust reddening and W_r(CaII K) (W_r(NaI 5891)),
finding that 33% (24%) of the absorbers are inconsistent with the best-fit
Milky Way E(B-V)-W_r relations at >3sigma significance.Comment: 38 pages, 16 figures, 4 tables. Accepted to Ap