975 research outputs found
Genetic analysis of epidermal growth factor action: assignment of human epidermal growth factor receptor gene to chromosome 7.
ALLSMOG: an APEX Low-redshift Legacy Survey for MOlecular Gas. I - molecular gas scaling relations, and the effect of the CO/H2 conversion factor
We present ALLSMOG, the APEX Low-redshift Legacy Survey for MOlecular Gas.
ALLSMOG is a survey designed to observe the CO(2-1) emission line with the APEX
telescope, in a sample of local galaxies (0.01 < z < 0.03), with stellar masses
in the range 8.5 < log(M*/Msun) < 10. This paper is a data release and initial
analysis of the first two semesters of observations, consisting of 42 galaxies
observed in CO(2-1). By combining these new CO(2-1) emission line data with
archival HI data and SDSS optical spectroscopy, we compile a sample of low-mass
galaxies with well defined molecular gas masses, atomic gas masses, and
gas-phase metallicities. We explore scaling relations of gas fraction and gas
consumption timescale, and test the extent to which our findings are dependent
on a varying CO/H2 conversion factor. We find an increase in the H2/HI mass
ratio with stellar mass which closely matches semi-analytic predictions. We
find a mean molecular gas fraction for ALLSMOG galaxies of MH2/M* = (0.09 -
0.13), which decreases with stellar mass. We measure a mean molecular gas
consumption timescale for ALLSMOG galaxies of 0.4 - 0.7 Gyr. We also confirm
the non-universality of the molecular gas consumption timescale, which varies
(with stellar mass) from ~100 Myr to ~2 Gyr. Importantly, we find that the
trends in the H2/HI mass ratio, gas fraction, and the non-universal molecular
gas consumption timescale are all robust to a range of recent
metallicity-dependent CO/H2 conversion factors.Comment: 25 pages, 15 figures. Accepted for publication in MNRA
ALMA observations of atomic carbon in z~4 dusty star-forming galaxies
We present ALMA [CI]() (rest frequency 492 GHz) observations for a
sample of 13 strongly-lensed dusty star-forming galaxies originally discovered
at 1.4mm in a blank-field survey by the South Pole Telescope. We compare these
new data with available [CI] observations from the literature, allowing a study
of the ISM properties of extreme dusty star-forming galaxies spanning
a redshift range . Using the [CI] line as a tracer of the molecular
ISM, we find a mean molecular gas mass for SPT-DSFGs of
M. This is in tension with gas masses derived via low- CO
and dust masses; bringing the estimates into accordance requires either (a) an
elevated CO-to-H conversion factor for our sample of and a gas-to-dust ratio , or (b) an high carbon abundance . Using observations of a range of additional atomic
and molecular lines (including [CI], [CII], and multiple transitions of CO), we
use a modern Photodissociation Region code (3D-PDR) to assess the physical
conditions (including the density, UV radiation field strength, and gas
temperature) within the ISM of the DSFGs in our sample. We find that the ISM
within our DSFGs is characterised by dense gas permeated by strong UV fields.
We note that previous efforts to characterise PDR regions in DSFGs may have
significantly underestimated the density of the ISM. Combined, our analysis
suggests that the ISM of extreme dusty starbursts at high redshift consists of
dense, carbon-rich gas not directly comparable to the ISM of starbursts in the
local Universe.Comment: 21 pages, 12 figures. Accepted for publication in MNRA
ALMA constraints on the faint millimetre source number counts and their contribution to the cosmic infrared background
We have analysed 18 ALMA continuum maps in Bands 6 and 7, with rms down to
7.8Jy, to derive differential number counts down to 60Jy and
100Jy at 1.3 mm and 1.1 mm, respectively. The area
covered by the combined fields is at 1.1mm and at 1.3mm. We improved the source extraction method by
requiring that the dimension of the detected sources be consistent with the
beam size. This method enabled us to remove spurious detections that have
plagued the purity of the catalogues in previous studies. We detected 50 faint
sources with S/N3.5 down to 60Jy, hence improving the statistics by a
factor of four relative to previous studies. The inferred differential number
counts are at a 1.1 mm flux Jy, and at a 1.3
mm flux Jy. At the faintest flux limits,
i.e. 30Jy and 40Jy, we obtain upper limits on the differential number
counts of and , respectively. Our results provide a new
lower limit to CIB intensity of 17.2 at 1.1mm and of
12.9 at 1.3mm. Moreover, the flattening of the integrated
number counts at faint fluxes strongly suggests that we are probably close to
the CIB intensity. Our data imply that galaxies with SFR
certainly contribute less than 50% to the CIB while more than 50% of the CIB
must be produced by galaxies with . The differential
number counts are in nice agreement with recent semi-analytical models of
galaxy formation even as low as our faint fluxes. Consequently, this supports
the galaxy evolutionary scenarios and assumptions made in these models.Comment: 11 pages, 9 figures, A&A accepte
SPT0346-52: Negligible AGN Activity in a Compact, Hyper-starburst Galaxy at z = 5.7
We present Chandra ACIS-S and ATCA radio continuum observations of the
strongly lensed dusty, star-forming galaxy SPT-S J034640-5204.9 (hereafter
SPT0346-52) at = 5.656. This galaxy has also been observed with ALMA, HST,
Spitzer, Herschel, APEX, and the VLT. Previous observations indicate that if
the infrared (IR) emission is driven by star formation, then the inferred
lensing-corrected star formation rate ( 4500 M_{\sun} yr) and
star formation rate surface density ( 2000 M_{\sun}
{yr^{-1}} {kpc^{-2}}) are both exceptionally high. It remained unclear from
the previous data, however, whether a central active galactic nucleus (AGN)
contributes appreciably to the IR luminosity. The {\it Chandra} upper limit
shows that SPT0346-52 is consistent with being star-formation dominated in the
X-ray, and any AGN contribution to the IR emission is negligible. The ATCA
radio continuum upper limits are also consistent with the FIR-to-radio
correlation for star-forming galaxies with no indication of an additional AGN
contribution. The observed prodigious intrinsic IR luminosity of (3.6
0.3) 10 L_{\sun} originates almost solely from vigorous star
formation activity. With an intrinsic source size of 0.61 0.03 kpc,
SPT0346-52 is confirmed to have one of the highest of any known
galaxy. This high , which approaches the Eddington limit for a
radiation pressure supported starburst, may be explained by a combination of
very high star formation efficiency and gas fraction.Comment: 8 pages, 6 figures, accepted for publication in Ap
Sub-kiloparsec Imaging of Cool Molecular Gas in Two Strongly Lensed Dusty, Star-Forming Galaxies
We present spatially-resolved imaging obtained with the Australia Telescope
Compact Array (ATCA) of three CO lines in two high-redshift gravitationally
lensed dusty star-forming galaxies, discovered by the South Pole Telescope.
Strong lensing allows us to probe the structure and dynamics of the molecular
gas in these two objects, at z=2.78 and z=5.66, with effective source-plane
resolution of less than 1kpc. We model the lensed emission from multiple CO
transitions and the dust continuum in a consistent manner, finding that the
cold molecular gas as traced by low-J CO always has a larger half-light radius
than the 870um dust continuum emission. This size difference leads to up to 50%
differences in the magnification factor for the cold gas compared to dust. In
the z=2.78 galaxy, these CO observations confirm that the background source is
undergoing a major merger, while the velocity field of the other source is more
complex. We use the ATCA CO observations and comparable resolution Atacama
Large Millimeter/submillimeter Array dust continuum imaging of the same objects
to constrain the CO-H_2 conversion factor with three different procedures,
finding good agreement between the methods and values consistent with those
found for rapidly star-forming systems. We discuss these galaxies in the
context of the star formation - gas mass surface density relation, noting that
the change in emitting area with observed CO transition must be accounted for
when comparing high-redshift galaxies to their lower redshift counterparts.Comment: 14 pages, 7 figures; accepted for publication in Ap
The Rest-Frame Submillimeter Spectrum of High-Redshift, Dusty, Star-Forming Galaxies
We present the average rest-frame spectrum of high-redshift dusty,
star-forming galaxies from 250-770GHz. This spectrum was constructed by
stacking ALMA 3mm spectra of 22 such sources discovered by the South Pole
Telescope and spanning z=2.0-5.7. In addition to multiple bright spectral
features of 12CO, [CI], and H2O, we also detect several faint transitions of
13CO, HCN, HNC, HCO+, and CN, and use the observed line strengths to
characterize the typical properties of the interstellar medium of these
high-redshift starburst galaxies. We find that the 13CO brightness in these
objects is comparable to that of the only other z>2 star-forming galaxy in
which 13CO has been observed. We show that the emission from the high-critical
density molecules HCN, HNC, HCO+, and CN is consistent with a warm, dense
medium with T_kin ~ 55K and n_H2 >~ 10^5.5 cm^-3. High molecular hydrogen
densities are required to reproduce the observed line ratios, and we
demonstrate that alternatives to purely collisional excitation are unlikely to
be significant for the bulk of these systems. We quantify the average emission
from several species with no individually detected transitions, and find
emission from the hydride CH and the linear molecule CCH for the first time at
high redshift, indicating that these molecules may be powerful probes of
interstellar chemistry in high-redshift systems. These observations represent
the first constraints on many molecular species with rest-frame transitions
from 0.4-1.2mm in star-forming systems at high redshift, and will be invaluable
in making effective use of ALMA in full science operations.Comment: 19 pages, 10 figures (2 in appendices); accepted for publication in
Ap
The Ursinus Weekly, December 11, 1950
Jeckely calls for resistance to communism • Sheeder talks at Trinity • Juniors choose 1952 Ruby heads • Chaplain to conduct communion • Y group discusses Atlantic Union plan • Red Cross unit plays host to area chapters • Snow Ball opens Fall social season • Students, faculty give blood to Red Cross • Three seniors admitted to dramatic honor frat • Former Ursinus coach dies in auto accident • Over 200 combine to present annual Messiah production • Only memories and souvenirs remain of seniors\u27 colorful formal dance • Warren W. Walters is the official engineer, the man-on-the-spot when trouble arises • French Club holds annual Xmas party • Nachrichten Deutschen Verein • Mack re-elected • Frosberg announces jobs open to grads • Commercialized Christmas forms basis of writer\u27s satire on holiday theme • Storm plays havoc on Ursinus campus • Library has tea • Bears win second 67-38 over Temple Pharmacy • Matmen work out for coming season • Grizzlies whip Crusaders 102-71 as records fall: Bears\u27 fiery attack breaks team mark after absorbing setback by Lycoming • Girls elect Keyser basketball captain • Hooper elected as 1951 hockey captain • Derago leads district scoring; Seibel fourth • Banquet, dance to top pre-holiday festivities • Chess team wins • Thirty couples enjoy reopening of Cafe Pigalle on Saturday • Y conducts Xmas vespers • German Club fetes • Duryea holds tea • Sophs pick committee to decorate at banquet • Lit reading to be held Tuesday • Glessner addresses guildhttps://digitalcommons.ursinus.edu/weekly/1555/thumbnail.jp
On the triple nature of the X-ray source 4U2129+47 (= V1727 Cyg)
Context. In quiescence, the proposed optical counterpart to the neutron star
low mass X-ray binary 4U 2129+47 (V1727 Cyg) shows a spectrum consistent with a
late F-type subgiant and no radial velocity variations on the 5.24 hour binary
period. This could imply that V1727 Cyg is a chance line of sight interloper.
Radial velocity measurements, however, showed evidence for a longer term ~40
km/s shift, which suggested that 4U 2129+47 could be a hierarchical triple
system, with the F-type star in a wide orbit about the inner low mass X-ray
binary. Aims. In order to confirm the long-term radial velocity shift reported
in Garcia et al. (1989) and its amplitude, we obtained spectroscopic
observations of V1727 Cyg during 1996 and 1998 with the William Herschel
Telescope using the ISIS spectrograph. Methods. We determined radial velocities
from the ISIS spectra by means of the cross-correlation technique with a
template spectrum. Results. The resulting radial velocities show variations
with a maximum amplitude of ~40 km/s, confirming previous results and
supporting the F-type star as being the third body in a hierarchical triple
system. The odds that this star could be an interloper are ~3e-6Comment: 3 Pages, 2 Figures. Revised version in form accepted for publication
in A&
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