8 research outputs found
A spectroscopic measure of the star-formation rate density in dwarf galaxies at z~1
We use a K-selected (22.5 < K_AB < 24.0) sample of dwarf galaxies (8.4 <
log(M*/Msun) < 10) at 0.89<z<1.15 in the Chandra Deep Field South (CDFS) to
measure their contribution to the global star-formation rate density (SFRD), as
inferred from their [OII] flux. By comparing with [OII]-based studies of higher
stellar mass galaxies, we robustly measure a turnover in the [OII] luminosity
density at a stellar mass of M~10^10 Msun. By comparison with the [OII]-based
SFRD measured from the Sloan Digital Sky Survey we confirm that, while the SFRD
of the lowest-mass galaxies changes very little with time, the SFRD of more
massive galaxies evolves strongly, such that they dominate the SFRD at z = 1.Comment: Accepted for publication in MNRAS Letters. 6 pages, 2 figure
The Redshift One LDSS-3 Emission line Survey (ROLES) II: Survey method and z~1 mass-dependent star-formation rate density
Motivated by suggestions of 'cosmic downsizing', in which the dominant
contribution to the cosmic star formation rate density (SFRD) proceeds from
higher to lower mass galaxies with increasing cosmic time, we describe the
design and implementation of the Redshift One LDSS3 Emission line Survey
(ROLES). ROLES is a K-selected (22.5 < K_AB < 24.0) survey for dwarf galaxies
[8.5<log(M*/Msun)< 9.5] at 0.89 < z < 1.15 drawn from two extremely deep fields
(GOODS-S and MS1054-FIRES). Using the [OII]3727 emission line, we obtain
redshifts and star-formation rates (SFRs) for star-forming galaxies down to a
limit of ~0.3 Msun/yr. We present the [OII] luminosity function measured in
ROLES and find a faint end slope of alpha_faint ~ -1.5, similar to that
measured at z~0.1 in the SDSS. By combining ROLES with higher mass surveys, we
measure the SFRD as a function of stellar mass using [OII] (with and without
various empirical corrections), and using SED-fitting to obtain the SFR from
the rest-frame UV luminosity for galaxies with spectroscopic redshifts. Our
best estimate of the corrected [OII]-SFRD and UV SFRD both independently show
that the SFRD evolves equally for galaxies of all masses between z~1 and z~0.1.
The exact evolution in normalisation depends on the indicator used, with the
[OII]-based estimate showing a change of a factor of ~2.6 and the UV-based a
factor of ~6. We discuss possible reasons for the discrepancy in normalisation
between the indicators, but note that the magnitude of this uncertainty is
comparable to the discrepancy between indicators seen in other z~1 works. Our
result that the shape of the SFRD as a function of stellar mass (and hence the
mass range of galaxies dominating the SFRD) does not evolve between z~1 and
z~0.1 is robust to the choice of indicator. [abridged]Comment: Resubmitted to MNRAS following first referee report. 20 pages, 16
figures. High resolution version available at
http://astro.uwaterloo.ca/~dgilbank/papers/roles2.pd
Comparative analysis of authorship trends in the Journal of Hand Surgery European and American volumes: A bibliometric analysis
Background
The purpose of this study was to better understand the authorship publishing trends in the field of hand surgery. To accomplish this, a comparative analysis was completed between the European and American volumes of the Journal of Hand Surgery (JHSE and JHSA) over the past three decades. Well-established bibliometric methods were used to examine one representative year from each of the past three decades. The focus of the study was to examine changes in author gender over time as well as to compare authorship trends across the two volumes.
Materials and methods
All JHSA and JHSE publications from 1985, 1995, 2005, and 2015 were placed into a Microsoft Excel spreadsheet. Data was collected for each publication including the gender of first and corresponding authors, corresponding author position, corresponding author country of origin, number of credited institutions, authors, printed pages, and references. Countries were grouped by regions.
Results
A total of 450 and 763 manuscripts from JHSE and JHSA, respectively, met inclusion criteria. JHSE and JHSA both showed increases in most variables analyzed over time. Both journals showed an increase in female first and corresponding authors. JHSE and JHSA displayed a rise in collaboration between institutions and countries.
Conclusions
Both JHSE and JHSA display increasing female inclusion in the hand surgery literature, which has traditionally been a male dominated field. The observed increase in collaboration between institutions and countries is likely linked to advances in technology that allow sharing of information more conveniently and reliably than was previously possible. As further advances are made socially and technologically, hopefully these trends will continue, leading to faster and higher quality research being generated in the field of hand surgery
The local star-formation rate density: assessing calibrations using [OII], Ha and UV luminosities
We explore the use of simple star-formation rate (SFR) indicators (such as
may be used in high-redshift galaxy surveys) in the local Universe using [OII],
Ha, and u-band luminosities from the deeper 275 deg^2 Stripe 82 subsample of
the Sloan Digital Sky Survey (SDSS) coupled with UV data from the Galaxy
Evolution EXplorer satellite (GALEX). We examine the consistency of such
methods using the star-formation rate density (SFRD) as a function of stellar
mass in this local volume, and quantify the accuracy of corrections for dust
and metallicity on the various indicators. Rest-frame u-band promises to be a
particularly good SFR estimator for high redshift studies since it does not
require a particularly large or sensitive extinction correction, yet yields
results broadly consistent with more observationally expensive methods. We
suggest that the [OII]-derived SFR, commonly used at higher redshifts (z~1),
can be used to reliably estimate SFRs for ensembles of galaxies, but for high
mass galaxies (log(M*/Msun)>10), a larger correction than is typically used is
required to compensate for the effects of metallicity dependence and dust
extinction. We provide a new empirical mass-dependent correction for the
[OII]-SFR.Comment: 22 pages, 16 figures. This version corrects typos in equations 2, 7,
and 9 of the published version, as described in the MNRAS Erratum. Published
results are unaffected. A simple piece of IDL Code for applying the
mass-dependent correction to [OII] SFR available from
http://astro.uwaterloo.ca/~dgilbank/data/corroii.pr
Skeletal adaptations in young male mice after 4 weeks aboard the International Space Station
Gravity has an important role in both the development and maintenance of bone mass. This is most evident in the rapid and intense bone loss observed in both humans and animals exposed to extended periods of microgravity in spaceflight. Here, cohabitating 9-week-old male C57BL/6 mice resided in spaceflight for ~4 weeks. A skeletal survey of these mice was compared to both habitat matched ground controls to determine the effects of microgravity and baseline samples in order to determine the effects of skeletal maturation on the resulting phenotype. We hypothesized that weight-bearing bones would experience an accelerated loss of bone mass compared to non-weight-bearing bones, and that spaceflight would also inhibit skeletal maturation in male mice. As expected, spaceflight had major negative effects on trabecular bone mass of the following weight-bearing bones: femur, tibia, and vertebrae. Interestingly, as opposed to the bone loss traditionally characterized for most weight-bearing skeletal compartments, the effects of spaceflight on the ribs and sternum resembled a failure to accumulate bone mass. Our study further adds to the insight that gravity has site-specific influences on the skeleton