1,457 research outputs found
Luminosities of H alpha emitting regions in a pair of interacting galaxies in the Bootes void
Luminosities of H alpha emission from a pair of interacting galaxies in the low density environment of the Bootes void are presented. CG 692 (IRAS 1519+5050) has an H alpha luminosity of 2 x 10(exp 42) ergs s(exp -1), indicating a star formation rate of 18.4 solar mass yr(exp -1). Individual extranuclear H alpha regions have luminosities of approximately 10(exp 40) ergs s(exp -1). These luminosities are similar to those found for H II regions in bright, late-type galaxies in more densely populated parts of the Universe
Total Molecular Gas Masses of Planck - Herschel Selected Strongly Lensed Hyper Luminous Infrared Galaxies
We report the detection of CO(1 - 0) line emission from seven Planck and
Herschel selected hyper luminous (LIR(8-1000um) > 10^13Lsun) infrared galaxies
with the Green Bank Telescope (GBT). CO(1 - 0) measurements are a vital tool to
trace the bulk molecular gas mass across all redshifts. Our results place tight
constraints on the total gas content of these most apparently luminous high-z
star-forming galaxies (apparent IR luminosities of LIR > 10^(13-14) Lsun),
while we confirm their predetermined redshifts measured using the Large
Millimeter Telescope, LMT (zCO = 1.33 - 3.26). The CO(1 - 0) lines show similar
profiles as compared to Jup = 2 -4 transitions previously observed with the
LMT. We report enhanced infrared to CO line luminosity ratios of
= 110 (pm 22) Lsun(K km s^-1 pc^-2)^-1 compared to normal
star-forming galaxies, yet similar to those of well-studied IR-luminous
galaxies at high-z. We find average brightness temperature ratios of =
0.93 (2 sources), = 0.34 (5 sources), and = 0.18 (1 source). The
r31 and r41 values are roughly half the average values for SMGs. We estimate
the total gas mass content as uMH2 = (0.9 - 27.2) x 10^11(alphaCO/0.8)Msun,
where u is the magnification factor and alphaCO is the CO line luminosity to
molecular hydrogen gas mass conversion factor. The rapid gas depletion times
are, on average, tau = 80 Myr, which reveal vigorous starburst activity, and
contrast the Gyr depletion timescales observed in local, normal star-forming
galaxies.Comment: published in MNRAS, 9pages, 5fig
The Nature of Compact Galaxies in the Hubble Deep Field (II): Spectroscopic Properties and Implications for the Evolution of the Star Formation Rate Density of the Universe
We present a spectroscopic study of 51 compact field galaxies with redshifts
z < 1.4 and apparent magnitudes I < 23.74 in the flanking fields of the Hubble
Deep Field. These galaxies are compact in the sense that they have small
apparent half-light radii (r_e < 0.5 arcsec) and high surface brightnesses
(SB_e < 22.2 mag arcsec^-2). The spectra, taken at the Keck telescope, show
emission lines in 88% of our sample, and only absorption lines in the remaining
12%. Emission-line profiles are roughly Gaussian with velocity widths that
range from the measurement limit of sigma = 35 km s^-1 to 150 km s^-1.
Rest-frame [OII]3727 equivalent widths range from 5A to 94A , yielding star
formation rates (SFR) of 0.1 to 14 M yr^-1. The analysis of various line
diagnostic diagrams reveals that 60% of compact emission-line galaxies have
velocity widths, excitations, Hbeta luminosities, SFRs, and mass-to-light
ratios characteristic of young star-forming HII galaxies. The remaining 40%
form a more heterogeneous class of evolved starbursts, similar to local
starburst disk galaxies. We find that, although the compact galaxies at z>0.7
have similar SFRs per unit mass to those at z<0.7, they are on average 10 times
more massive. Our sample implies a lower limit for the global comoving SFR
density of 0.004 M yr^-1 Mpc^-3 at z = 0.55, and 0.008 M yr^-1 Mpc^-3 at z =
0.85 (assuming Salpeter IMF, Ho = 50 km s^-1 Mpc^-1, and qo = 0.5). These
values, when compared to estimates for a sample of local compact galaxies
selected in a similar fashion, support a history of the universe in which the
SFR density declines by a factor 10 from z = 1 to today.Comment: LaTeX, 38 pages, 2 tables, 10 postscript figures. Accepted for
publication in the Astrophysical Journa
Optical Morphologies of Millijansky Radio Galaxies Observed by HST and in the VLA FIRST Survey
We report on a statistical study of the 51 radio galaxies at the millijansky
flux level from the Faint Images of the Radio Sky at Twenty centimeters,
including their optical morphologies and structure obtained with the Hubble
Space Telescope. Our optical imaging is significantly deeper (~2 mag) than
previous studies with the superior angular resolution of space-based imaging.
We that find 8/51 (16%) of the radio sources have no optically identifiable
counterpart to AB~24 mag. For the remaining 43 sources, only 25 are
sufficiently resolved in the HST images to reliably assign a visual
classification: 15 (60%) are elliptical galaxies, 2 (8%) are late-type spiral
galaxies, 1 (4%) is an S0, 3 (12%) are point-like objects (quasars), and 4
(16%) are merger systems. We find a similar distribution of optical types with
measurements of the Sersic index. The optical magnitude distribution of these
galaxies peaks at I~20.7+-0.5 AB mag, which is ~3 mag brighter than the depth
of our typical HST field and is thus not due to the WFPC2 detection limit. This
supports the luminosity-dependent density evolutionary model, where the
majority of faint radio galaxies typically have L*-optical luminosities and a
median redshift of z~0.8 with a relatively abrupt redshift cut-off at z>~2. We
discuss our results in the context of the evolution of elliptical galaxies and
active galactic nuclei.Comment: 20 pages, 8 figures, 51 galaxy images, and 5 tables. Uses
emulateapj.cls and natbib.sty. Accepted to ApJS. High resolution images are
available upon reques
Risk Factors for Suboptimal Antiretroviral Therapy Adherence in HIV-Infected Adolescents in Gaborone, Botswana: A Pilot Cross-Sectional Study
Objective: Little is known about factors associated with suboptimal antiretroviral treatment (ART) adherence among adolescents in Sub-Saharan Africa. Our objective was to determine the level of ART adherence and predictors of non-adherence among human immunodeficiency virus (HIV)-infected adolescents at the Botswana-Baylor Children\u27s Clinical Centre of Excellence in Gaborone, Botswana.
Methods: In a cross-sectional study, 82 HIV-infected adolescents receiving ART and their caregivers were administered a structured questionnaire. The patient\u27s clinical information was retrieved from medical records. Outcome measures included excellent pill count ART adherence (\u3e95%) and virologic suppression (HIV viral load \u3c400 copies/mL). Multivariate logistic regression analysis was performed to identify independent predictors of ART non-adherence.
Results: The overall median (interquartile range) ART adherence was 99% (96.5–100) (N = 82). Seventy-six percent of adolescents had excellent pill count ART adherence levels and 94% achieved virologic suppression. Male adolescents made up 65% of the non-adherent group (P = 0.02). Those who displayed suboptimal ART adherence were more likely to report having ever missed ART doses due to failure to pick up medication at the pharmacy (30.0% versus 9.7%, P = 0.03). In the multivariate logistic regression model, male sex (odds ratio [OR] 3.29, 95% confidence interval [CI] 1.13–9.54; P = 0.03) was the only factor which was independently associated with suboptimal ART adherence.
Conclusions: A high proportion of HIV-infected adolescents studied had excellent ART adherence and virologic suppression, with male adolescents at higher risk of suboptimal adherence than females. Further research to investigate how gender relates to suboptimal adherence may aid in the design of targeted intervention strategies
The living and the dead; an investigation into the status of erasure within the floor of Bath Abbey
The floor of Bath Abbey offers a singular test of authenticity. Nineteenth century repairs and additions caused horizontal grave markers, which comprise the majority of the Abbey’s floor, to become separated from the burial sites they were intended to memorialize. A century and a half of further occupation has had the effect of removing many inscriptions as surfaces are worn smooth. The result is a patchwork of unintended edits and accidental poetry. This paper explores the notions of authenticity, essence, memorial and erasure as they pertain to the Abbey floor, in particular with regard to the role the body plays in inhabiting/eroding the floor—from both above and below. The author argues that the stones which are most out of place or worn to a state of erasure are no less authentic than their intact equivalents, but that they can be considered to have moved to another state of authenticity rich in resonance and meaning. This paper, in short, is a defense of erasure and that erosion through occupation may be considered a form of social memory; indeed, the marks of walking become the inscription. In other words, the undesigned (erasure, the cutting and repositioning of ledger stones, the missing inscriptions) becomes considered not as a form of dirt but as the positive traces of on-going and meaningful occupation
Evaluation of organic markers for chemical mass balance source apportionment at the Fresno Supersite
International audienceSources of PM2.5 at the Fresno Supersite during high PM2.5 episodes occurring from 15 December 2000?3 February 2001 were estimated with the Chemical Mass Balance (CMB) receptor model. The ability of source profiles with organic markers to distinguish motor vehicle, residential wood combustion (RWC), and cooking emissions was evaluated with simulated data. Organics improved the distinction between gasoline and diesel vehicle emissions and allowed a more precise estimate of the cooking source contribution. Sensitivity tests using average ambient concentrations showed that the gasoline vehicle contribution was not resolved without organics. Organics were not required to estimate hardwood contributions. The most important RWC marker was the water-soluble potassium ion. The estimated cooking contribution did not depend on cholesterol because its concentrations were below the detection limit in most samples. Winter time source contributions were estimated by applying the CMB model to individual and average sample concentrations. RWC was the largest source, contributing 29?31% of measured PM2.5. Hardwood and softwood combustion accounted for 16?17% and 12?15%, respectively. Secondary ammonium nitrate and motor vehicle emissions accounted for 31?33% and 9?15%, respectively. The gasoline vehicle contribution (3?10%) was comparable to the diesel vehicle contribution (5?6%). The cooking contribution was 5?19% of PM2.5. Fresno source apportionment results were consistent with those estimated in previous studies
Deep 1.1 mm-wavelength imaging of the GOODS-South field by AzTEC/ASTE -- II. Redshift distribution and nature of the submillimetre galaxy population
We report the results of the counterpart identification and a detailed
analysis of the physical properties of the 48 sources discovered in our deep
1.1mm wavelength imaging survey of the GOODS-South field using the AzTEC
instrument on the Atacama Submillimeter Telescope Experiment (ASTE). One or
more robust or tentative counterpart candidate is found for 27 and 14 AzTEC
sources, respectively, by employing deep radio continuum, Spitzer MIPS & IRAC,
and LABOCA 870 micron data. Five of the sources (10%) have two robust
counterparts each, supporting the idea that these galaxies are strongly
clustered and/or heavily confused. Photometric redshifts and star formation
rates (SFRs) are derived by analyzing UV-to-optical and IR-to-radio SEDs. The
median redshift of z~2.6 is similar to other earlier estimates, but we show
that 80% of the AzTEC-GOODS sources are at z>2, with a significant high
redshift tail (20% at z>3.3). Rest-frame UV and optical properties of AzTEC
sources are extremely diverse, spanning 10 magnitude in the i- and K-band
photometry with median values of i=25.3 and K=22.6 and a broad range of red
colour (i-K=0-6). These AzTEC sources are some of the most luminous galaxies in
the rest-frame optical bands at z>2, with inferred stellar masses of (1-30) x
10^{10} solar masses and UV-derived star formation rates of SFR(UV) > 10-1000
solar masses per year. The IR-derived SFR, 200-2000 solar masses per year, is
independent of redshift or stellar mass. The resulting specific star formation
rates, SSFR = 1-100 per Gyr, are 10-100 times higher than similar mass galaxies
at z=0, and they extend the previously observed rapid rise in the SSFR with
redshift to z=2-5. These galaxies have a SFR high enough to have built up their
entire stellar mass within their Hubble time. We find only marginal evidence
for an AGN contribution to the near-IR and mid-IR SEDs. (abridged)Comment: 31 pages including 14 figures, accepted for publication in the MNRAS.
A higher quality Figure 1 is also included as Figure1.jp
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