330 research outputs found
Evidence for Cold Accretion: Primitive Gas Flowing onto a Galaxy at z~0.274
We present UV and optical observations from the Cosmic Origins Spectrograph
on the Hubble Space Telescope and Keck of a z= 0.27395 Lyman limit system (LLS)
seen in absorption against the QSO PG1630+377. We detect H I absorption with
log N(HI)=17.06\pm0.05 as well as Mg II, C III, Si III, and O VI in this
system. The column densities are readily explained if this is a multi-phase
system, with the intermediate and low ions arising in a very low metallicity
([Mg/ H] =-1.71 \pm 0.06) photoionized gas. We identify via Keck spectroscopy
and Large Binocular Telescope imaging a 0.3 L_* star-forming galaxy projected
37 kpc from the QSO at nearly identical redshift (z=0.27406, \Delta v = -26
\kms) with near solar metallicity ([O/ H]=-0.20 \pm 0.15). The presence of very
low metallicity gas in the proximity of a near-solar metallicity, sub-L_*
galaxy strongly suggests that the LLS probes gas infalling onto the galaxy. A
search of the literature reveals that such low metallicity LLSs are not
uncommon. We found that 50% (4/8) of the well-studied z < 1 LLSs have
metallicities similar to the present system and show sub-L_* galaxies with rho
< 100 kpc in those fields where redshifts have been surveyed. We argue that the
properties of these primitive LLSs and their host galaxies are consistent with
those of cold mode accretion streams seen in galaxy simulations.Comment: Accepted for publication in the Astrophysical Journa
Multiphase Gas In Galaxy Halos: The OVI Lyman-limit System toward J1009+0713
We have serendipitously detected a strong O VI-bearing Lyman limit system at
z_abs = 0.3558 toward the QSO J1009+0713 (z_em = 0.456) in our survey of
low-redshift galaxy halos with the Hubble Space Telescope's Cosmic Origins
Spectrograph. Its rest-frame equivalent width of W_r = 835 +/- 49 mA is the
highest for an intervening absorber yet detected in any low-redshift QSO
sightline, with absorption spanning 400 km s^-1 in its rest frame. HST/WFC3
images of the galaxy field show that the absorber is associated with two
galaxies lying at 14 and 46 kpc from the QSO line of sight. The bulk of the
absorbing gas traced by H I resides in two strong, blended component groups
that possess a total logN(HI) = 18 - 18.8. The ion ratios and column densities
of C, N, O, Mg, Si, S, and Fe, except the O VI, can be accommodated into a
simple photoionization model in which diffuse, low-metallicity halo gas is
exposed to a photoionizing field from stars in the nearby galaxies that
propagates into the halo at 10% efficiency. We constrain the metallicity firmly
within the range 0.1 - 1 Zsun, and photoionization modeling indirectly
indicates a subsolar metallicity of 0.05 - 0.5 Zsun. The appearance of strong O
VI and nine Mg II components and our review of similar systems in the
literature support the "interface" picture of high-velocity O VI: the total
strength of the O VI shows a positive correlation with the number of detected
components in the low-ionization gas, however the total O VI column densities
still far exceed the values expected from interface models for the number of
detected clouds.Comment: 20 pages, 11 figures, accepted for publication in Ap
An Adaptation of Pavlovian-to-Instrumental Transfer (PIT) Methodology to Examine the Energizing Effects of Reward-Predicting Cues on Behavior in Young Adults
There is growing recognition that much of human behavior is governed by the presence of classically conditioned cues. The Pavlovian-to-Instrumental Transfer (PIT) paradigm offers a way to measure the effects of classically conditioned stimuli on behavior. In the current study, a novel behavioral task, an adaptation of the PIT framework, was developed for use in conjunction with an fMRI classical conditioning task. Twenty-four healthy young adults completed (1) instrumental training, (2) Pavlovian conditioning, and (3) a Transfer test. During instrumental training, participants learned to apply force to a handgrip to win money from slot machines pictured on a computer screen. During Pavlovian conditioning, slot machines appeared with one of two abstract symbols (cues), one symbol was predictive of monetary reward. During the Transfer test, participants again applied force to a handgrip to win money. This time, the slot machines were presented with the Pavlovian cues, but with the outcomes hidden. The results indicated increased effort on the instrumental task, i.e. higher response frequency and greater force, in the presence of the reward-predicting cue. Our findings add to the growing number of studies demonstrating PIT effects in humans. This new paradigm is effective in measuring the effects of a conditioned stimulus on behavioral activation
The Gas-Galaxy Connection at z = 0.35: OVI and HI Absorption Towards J0943+0531
We present observations of HI and OVI absorption systems proximate to a
galaxy at z_gal = 0.3529. The absorption was detected serendipitously in Cosmic
Origins Spectrograph observations of the low-z QSO J0943+0531 (z_qso = 0.564).
The data show two separate clouds along the sightline at an impact parameter of
95kpc from the galaxy. The first is likely low-metallicity gas falling onto the
galaxy. This assessment is based on the high velocity offset of the cloud from
the galaxy (delta_v = 365kms) and the weak metal line absorption, combined with
photoionization modeling. The second cloud, with only a modest velocity
separation from the galaxy (delta_v = 85kms), exhibits very strong OVI
absorption qualitatively similar to OVI absorption seen in the Milky Way halo.
Collisional ionization equilibrium models are ruled out by the metal line
column density ratios. Photoionization modeling implies a length-scale for the
OVI cloud of ~0.1-1.2Mpc, which indicates the absorbing gas most likely resides
within the local filamentary structure. This system emphasizes that kinematic
association alone is not sufficient to establish a physical connection to
galaxies, even at small impact parameters and velocity separations.
Observations such as these, connecting galaxies with their gaseous
environments, are becoming increasingly important for understanding galaxy
evolution and provide constraints for cosmological simulations.Comment: ApJ in press. 11 pages, 7 figure
Methylphenidate modifies reward cue responses in adults with ADHD: An fMRI study
Attention deficit hyperactivity disorder (ADHD) has been associated with neural hyposensitivity to reward-predicting cues. Methylphenidate is widely used in the management of the disorder\u27s symptoms, but its effects on reward sensitivity in ADHD are unknown. The current study used fMRI to measure striatal responses to reward-predicting cues in adults with ADHD on and off methylphenidate and a control group, during a classical conditioning task. Responses to cued reward were also explored. Larger differences in the ventral striatum activation to reward cues versus non-reward cues were observed when the ADHD participants were on methylphenidate compared to placebo. In response to cued-reward outcome, an exploratory analysis showed methylphenidate reduced the BOLD time-series correlation between the dorsal striatum and dorsal medial prefrontal cortex. Methylphenidate\u27s therapeutic effects may be mediated by altering reward processing in individuals with ADHD
The effect of feedback on the emission properties of the Warm-Hot Intergalactic Medium
At present, 30-40 per cent of the baryons in the local Universe is still
undetected. According to theoretical predictions, this gas should reside in
filaments filling the large-scale structure (LSS) in the form of a Warm-Hot
Intergalactic Medium (WHIM), at temperatures of 10^5 - 10^7 K, thus emitting in
the soft X-ray energies via free-free interaction and line emission from heavy
elements. In this work we characterize the properties of the X-ray emission of
the WHIM, and the LSS in general, focusing on the influence of different
physical mechanisms, namely galactic winds (GWs), black-hole feedback and
star-formation, and providing estimates of possible observational constraints.
To this purpose we use a set of cosmological hydrodynamical simulations that
include a self-consistent treatment of star-formation and chemical enrichment
of the intergalactic medium, that allows us to follow the evolution of
different metal species. We construct a set of simulated light-cones to make
predictions of the emission in the 0.3-10 keV energy range. We obtain that GWs
increase by a factor of 2 the emission of both galaxy clusters and WHIM. The
amount of oxygen at average temperature and, consequently, the amount of
expected bright Ovii and Oviii lines is increased by a factor of 3 due to GWs
and by 20 per cent when assuming a top-heavy IMF. We compare our results with
current observational constraints and find that the emission from faint groups
and WHIM should account from half to all of the unresolved X-ray background in
the 1-2 keV band.Comment: 15 pages, 8 figures, 4 tables. Accepted for publication in the MNRAS.
Minor changes after referee repor
Self Management Activation Randomised Trial for Prostatitis (SMART-P): study protocol for a randomised controlled trial
<p>Abstract</p> <p>Background</p> <p>Chronic prostatitis otherwise known as chronic pelvic pain syndrome is a common urological diagnosis that causes many men significant morbidity and has a detrimental effect on their quality of life. Standard treatment with antibiotics and simple analgesia are often ineffective and many patients are managed by the chronic pain services.</p> <p>Cognitive behavioural therapy has been shown to be helpful in the management of many chronic diseases and has recently been proposed as an effective treatment for chronic prostatitis. Furthermore, a self management programme administered to groups of men with lower urinary tract symptoms has been shown to be more effective than standard treatments including surgery.</p> <p>Therefore, we have developed a cognitive behavioural therapy programme specifically for men with chronic prostatitis. This novel treatment approach will be compared to conventional therapy in the pain clinic such as atypical analgesia and local anaesthetic injections in the context of a randomised controlled trial.</p> <p>Methods/Design</p> <p>Men will be recruited from general urology outpatient clinics following the exclusion of other diagnoses that could be responsible for their symptoms. Men will be randomised to attend either a self management healthcare and education programme or to pain clinic referral alone. The self management programme will be administered by a clinical psychologist to small groups of men over six consecutive weekly sessions each lasting two hours. Patients will be taught techniques of problem-solving and goal-setting and will learn coping mechanisms and how to modify catastrophic cognition.</p> <p>The primary outcome will be change from baseline in the National Institute of Health Chronic Prostatitis Symptom Index, a validated instrument for the assessment of men with chronic prostatitis. Secondary outcomes include generic quality of life scores and analgesic and drug usage. Outcomes will be assessed at 2, 6 and 12 months.</p> <p>Discussion</p> <p>If this group administered self management programme is shown to be effective in the treatment of men with chronic prostatitis it may become the new standard of care for these patients. Furthermore, it may be adapted for use in women with interstitial cystitis, a condition which is analogous to chronic prostatitis in men.</p> <p>Trial Registration</p> <p>Current Controlled Trials <a href="http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=ISRCTN21012555">ISRCTN21012555</a></p
The COS-Halos Survey: Keck LRIS and Magellan MagE Optical Spectroscopy
We present high signal-to-noise optical spectra for 67 low-redshift (0.1 < z
< 0.4) galaxies that lie within close projected distances (5 kpc < rho < 150
kpc) of 38 background UV-bright QSOs. The Keck LRIS and Magellan MagE data
presented here are part of a survey that aims to construct a statistically
sampled map of the physical state and metallicity of gaseous galaxy halos using
the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST). We
provide a detailed description of the optical data reduction and subsequent
spectral analysis that allow us to derive the physical properties of this
uniquely data-rich sample of galaxies. The galaxy sample is divided into 38
pre-selected L ~ L*, z ~ 0.2 "target" galaxies and 29 "bonus" galaxies that lie
in close proximity to the QSO sightlines. We report galaxy spectroscopic
redshifts accurate to +/- 30 km s-1, impact parameters, rest-frame colors,
stellar masses, total star formation rates, and gas-phase interstellar medium
oxygen abundances. When we compare the distribution of these galaxy
characteristics to those of the general low-redshift population, we find good
agreement. The L ~ L* galaxies in this sample span a diverse range of color
(1.0 < u-r < 3.0), stellar mass (10^9.5 < M/M_sun < 10^11.5), and SFRs (0.01 -
20 M_sun yr-1). These optical data, along with the COS UV spectroscopy,
comprise the backbone of our efforts to understand how halo gas properties may
correlate with their host galaxy properties, and ultimately to uncover the
processes that drive gas outflow and/or are influenced by gas inflow.Comment: 20 pages, 12 Figures, Submitted to ApJ
The luminosity of supernovae of type Ia from TRGB distances and the value of H_0
Distances from the tip of the red-giant branch (TRGB) in the halo Population
of galaxies - calibrated through RR Lyr stars as well as tied to Hipparcos
parallaxes and further supported by stellar models - are used to determine the
luminosity of six nearby type Ia supernovae (SN 2011fe, 2007sr, 1998bu, 1989B,
1972E, and 1937C). The result is M_V^corr = -19.41 +/- 0.05. If this value is
applied to 62 SNe Ia with 3000< v < 20,000 km/s a large-scale value of the
Hubble constant follows of H_0 = 64.0 +/- 1.6 +/- 2.0. The SN HST Project gave
H_0 = 62.3 +/- 1.3 +/- 5.0 from ten Cepheid-calibrated SNe Ia (Sandage et al.
2006). The agreement of young Population I (Cepheids) and old, metal-poor
Population II (TRGB) distance indicators is satisfactory. The combined weighted
result is H_0 = 63.7 +/- 2.3 (i.e. +/-3.6%). The result can also be reconciled
with WMAP5 data (Reid et al. 2010).Comment: 9 pages, 3 figures, 3 tables, accepted for publication in Astronomy
and Astrophysic
Shining Light on Merging Galaxies I: The Ongoing Merger of a Quasar with a `Green Valley' Galaxy
Serendipitous observations of a pair z = 0.37 interacting galaxies (one
hosting a quasar) show a massive gaseous bridge of material connecting the two
objects. This bridge is photoionized by the quasar (QSO) revealing gas along
the entire projected 38 kpc sightline connecting the two galaxies. The emission
lines that result give an unprecedented opportunity to study the merger process
at this redshift. We determine the kinematics, ionization parameter (log U ~
-2.5 +- 0.03), column density (N_H ~ 10^{21} cm^{-2}), metallicity ([M/H] ~
-0.20 +- 0.15), and mass (~ 10^8 Msun) of the gaseous bridge. We simultaneously
constrain properties of the QSO-host (M_DM>8.8x 10^{11} Msun) and its companion
galaxy (M_DM>2.1 x 10^{11} Msun; M_star ~ 2 x 10^{10} Msun; stellar burst
age=300-800 Myr; SFR~6 Msun/yr; and metallicity 12+log (O/H)= 8.64 +- 0.2). The
general properties of this system match the standard paradigm of a
galaxy-galaxy merger caught between first and second passage while one of the
galaxies hosts an active quasar. The companion galaxy lies in the so-called
`green valley', with a stellar population consistent with a recent starburst
triggered during the first passage of the merger and has no detectable AGN
activity. In addition to providing case-studies of quasars associated with
galaxy mergers, quasar/galaxy pairs with QSO-photoionized tidal bridges such as
this one offer unique insights into the galaxy properties while also
distinguishing an important and inadequately understood phase of galaxy
evolution.Comment: 23 pages, 12 figures, 5 tables, Submitted to ApJ, revised to address
referee's comment
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