1,723 research outputs found
The Spitzer c2d Survey of Nearby Dense Cores: III: Low Mass Star Formation in a Small Group, L1251B
We present a comprehensive study of a low-mass star-forming region,L1251B, at
wavelengths from the near-infrared to the millimeter. L1251B, where only one
protostar, IRAS 22376+7455, was known previously, is confirmed to be a small
group of protostars based on observations with the Spitzer Space Telescope. The
most luminous source of L1251B is located 5" north of the IRAS position. A
near-infrared bipolar nebula, which is not associated with the brightest object
and is located at the southeast corner of L1251B, has been detected in the IRAC
bands. OVRO and SMA interferometric observations indicate that the brightest
source and the bipolar nebula source in the IRAC bands are deeply embedded disk
sources.Submillimeter continuum observations with single-dish telescopes and
the SMA interferometric observations suggest two possible prestellar objects
with very high column densities. Outside of the small group, many young stellar
object candidates have been detected over a larger region of 12' x 12'.
Extended emission to the east of L1251B has been detected at 850 micron; this
"east core" may be a site for future star formation since no point source has
been detected with IRAC or MIPS. This region is therefore a possible example of
low-mass cluster formation, where a small group of pre- and protostellar
objects (L1251B) is currently forming, alongside a large starless core (the
east core).Comment: 35 pages, 15 figures, accepted for publication in ApJ, for the full
resolution paper, visit
"http://peggysue.as.utexas.edu/SIRTF/PAPERS/pap27.pub.pdf
The Spitzer c2d survey of Large, Nearby, Interstellar Clouds. V. Chamaeleon II Observed with IRAC
We present IRAC (3.6, 4.5, 5.8, and 8.0 micron) observations of the
Chamaeleon II molecular cloud. The observed area covers about 1 square degree
defined by . Analysis of the data in the 2005 c2d catalogs reveals a
small number of sources (40) with properties similar to those of young
stellaror substellar objects (YSOs). The surface density of these YSO
candidates is low, and contamination by background galaxies appears to be
substantial, especially for sources classified as Class I or flat SED. We
discuss this problem in some detail and conclude that very few of the candidate
YSOs in early evolutionary stages are actually in the Cha II cloud. Using a
refined set of criteria, we define a smaller, but more reliable, set of 24 YSO
candidates.Comment: 19 pages, 10 figures, in press Ap
Retreat dynamics of the eastern sector of the British–Irish Ice Sheet during the last glaciation
The findings of BRITICE‐CHRONO Transect 2 through the North Sea Basin and eastern England are reported. We define ice‐sheet marginal oscillation between ~31 and 16 ka, with seven distinctive former ice‐sheet limits (L1–7) constrained by Bayesian statistical analysis. The southernmost limit of the North Sea Lobe is recorded by the Bolders Bank Formation (L1; 25.8–24.6 ka). L2 represents ice‐sheet oscillation and early retreat to the northern edge of the Dogger Bank (23.5–22.2 ka), with the Garret Hill Moraine in north Norfolk recording a significant regional readvance to L3 at 21.5–20.8 ka. Ice‐marginal oscillations at ~26–21 ka resulted in L1, L2 and L3 being partially to totally overprinted. Ice‐dammed lakes related to L1–3, including Lake Humber, are dated at 24.1–22.3 ka. Ice‐sheet oscillation and retreat from L4 to L5 occurred between 19.7 and 17.3 ka, with grounding zone wedges marking an important transition from terrestrial to marine tidewater conditions, triggered by the opening of the Dogger Lake spillway between 19.9 and 17.5 ka. L6 relates to ice retreat under glacimarine conditions and final ice retreat into the Firth of Forth by 15.8 ka. L7 (~15 ka) represents an ice retreat from Bosies Bank into the Moray Firth
Sexual Orientation, Tobacco Use, and Tobacco Cessation Treatment-Seeking: Results from a National U.S. Survey
Despite higher rates of tobacco use and smoking-related diseases among sexual minorities, tobacco cessation treatment-seeking behaviors (e.g., medication, nicotine replacement products) remain poorly understood across sexual orientation subgroups. This study examines tobacco cessation treatment-seeking behaviors associated with DSM-5 tobacco use disorder (TUD) across the three major sexual orientation dimensions (identity, attraction, behavior) in U.S. adults. Prevalence estimates reflect data collected from a 2012–2013 national sample of adults 18 years and older. More than three-fourths of U.S. adults with TUD had never engaged in tobacco cessation treatment-seeking behaviors, regardless of sexual orientation. Despite having the highest rates of TUD, bisexual men and women had some of the lowest rates of tobacco cessation treatment-seeking. Men who identified as gay, reported same-sex attraction, or same-sex behaviors had the highest rates of tobacco cessation treatment-seeking. In contrast, women with same-sex attraction or same-sex behavior had higher rates of TUD but were less likely to engage in tobacco cessation treatment-seeking behaviors than women with only other-sex attraction or other-sex behavior, respectively. Heterosexual women were more likely to engage in tobacco cessation treatment-seeking than heterosexual men; this sex difference was not present for sexual minorities. Medications and nicotine replacement therapy products were the most prevalent forms of treatment-seeking. There were notable differences in tobacco cessation treatment-seeking behaviors based on sex and sexual orientation. Findings highlight the underutilization of tobacco cessation treatment-seeking among all U.S. adults and point to important factors to consider when working with sexual minorities who are trying to reduce or stop using tobacco
Recommended from our members
From soil to sequence: filling the critical gap in genome-resolved metagenomics is essential to the future of soil microbial ecology
Soil microbiomes are heterogeneous, complex microbial communities. Metagenomic analysis is generating vast amounts of data, creating immense challenges in sequence assembly and analysis. Although advances in technology have resulted in the ability to easily collect large amounts of sequence data, soil samples containing thousands of unique taxa are often poorly characterized. These challenges reduce the usefulness of genome-resolved metagenomic (GRM) analysis seen in other fields of microbiology, such as the creation of high quality metagenomic assembled genomes and the adoption of genome scale modeling approaches. The absence of these resources restricts the scale of future research, limiting hypothesis generation and the predictive modeling of microbial communities. Creating publicly available databases of soil MAGs, similar to databases produced for other microbiomes, has the potential to transform scientific insights about soil microbiomes without requiring the computational resources and domain expertise for assembly and binning
Prenatal exome sequencing in anomalous fetuses: new opportunities and challenges
We investigated the diagnostic and clinical performance of exome sequencing (ES) in fetuses with sonographic abnormalities with normal karyotype, microarray and, in some cases, normal gene specific sequencing
The Spitzer c2d Survey of Nearby Dense Cores: I: First Direct Detection of the Embedded Source in IRAM 04191+1522
We report the first detections of the Class 0 protostellar source IRAM
04191+1522 at wavelengths shortward of 60 microns with the Spitzer Space
Telescope. We see extended emission in the Spitzer images that suggests the
presence of an outflow cavity in the circumstellar envelope. We combine the
Spitzer observations with existing data to form a complete dataset ranging from
3.6 to 1300 microns and use these data to construct radiative transfer models
of the source. We conclude that the internal luminosity of IRAM 04191+1522,
defined to be the sum of the luminosity from the internal sources (a star and a
disk), is L_int = 0.08 +/- 0.04 L_sun, placing it among the lowest luminosity
protostars known. Though it was discovered before the launch of the Spitzer
Space Telescope, IRAM 04191+1522 falls within a new class of Very Low
Luminosity Objects being discovered by Spitzer. Unlike the two other
well-studied objects in this class, which are associated either with weak,
compact outflows or no outflows at all, IRAM 04191+1522 has a well-defined
molecular outflow with properties consistent with those expected based on
relations derived from higher luminosity (L_int > 1 L_sun) protostars. We
discuss the difficulties in understanding IRAM 04191+1522 in the context of the
standard model of star formation, and suggest a possible explanation for the
very low luminosity of this source.Comment: Accepted for publication in the Astrophysical Journal. 39 pages, 9
figures. See http://peggysue.as.utexas.edu/SIRTF/ for high-resolution figure
The Spitzer c2d Survey of Nearby Dense Cores: IV. Revealing the Embedded Cluster in B59
Infrared images of the dark cloud core B59 were obtained with the Spitzer
Space Telescope as part of the "Cores to Disks" Legacy Science project.
Photometry from 3.6-70 microns indicates at least 20 candidate low-mass young
stars near the core, more than doubling the previously known population. Out of
this group, 13 are located within about 0.1 pc in projection of the molecular
gas peak, where a new embedded source is detected. Spectral energy
distributions span the range from small excesses above photospheric levels to
rising in the mid-infrared. One other embedded object, probably associated with
the millimeter source B59-MMS1, with a bolometric luminosity L(bol) roughly 2
L(sun), has extended structure at 3.6 and 4.5 microns, possibly tracing the
edges of an outflow cavity. The measured extinction through the central part of
the core is A(V) greater than of order 45 mag. The B59 core is producing young
stars with a high efficiency
- …