1,422 research outputs found
Infrared photometric study of the massive star forming region S235 using Spitzer-IRAC and JHK observations
We present the {\it Spitzer}-IRAC images of the S235 star forming complex
that includes the East~1 & 2, Central and S235 A & B regions. In addition, we
present the near-infrared images of the S235 A & B regions. The IRAC photometry
reveals on-going star formation, with 86 Class 0/I and 144 Class II YSOs in the
entire S235 complex. Nearly 73% of these YSOs are present in clusters with a
maximum surface density of 120 YSOs/pc (in the vicinity of S235A & B
regions). A few YSOs, possibly in an arc-like formation, are identified towards
the south of S235A region, which may be speculated as an evidence for
magnetically super-critical collapse. One of the sources in the arc-like
formation, namely S235AB-MIR, seems to be a young, massive star that is still
accreting matter. SED modeling of some of the newly identified YSOs confirms
the classification made on the basis of IRAC colours. The IRAC ratio map of
Ch2/Ch4 traces clearly the Br emission associated with the HII region
of S235A within the horse-shoe envelope. Outside the horse-shoe structure, the
ratio map indicates shock-excited H emission. Br emission is also
seen around S235B (from the ratio map). The ratio map of Ch2/Ch4 reveals that
the source "e2s3" in the East~2 region may be associated with shock-excited
H emission outflow or jet. The SED modeling of this new source indicates
that it is a very young massive star that is not yet able to drive an HII
region.Comment: 19 pages; 13 figures; 8 tables. Accepted in MNRAS, Feb 201
Sky maps without anisotropies in the cosmic microwave background are a better fit to WMAP's uncalibrated time ordered data than the official sky maps
The purpose of this reanalysis of the WMAP uncalibrated time ordered data
(TOD) was two fold. The first was to reassess the reliability of the detection
of the anisotropies in the official WMAP sky maps of the cosmic microwave
background (CMB). The second was to assess the performance of a proposed
criterion in avoiding systematic error in detecting a signal of interest. The
criterion was implemented by testing the null hypothesis that the uncalibrated
TOD was consistent with no anisotropies when WMAP's hourly calibration
parameters were allowed to vary. It was shown independently for all 20 WMAP
channels that sky maps with no anisotropies were a better fit to the TOD than
those from the official analysis. The recently launched Planck satellite should
help sort out this perplexing result.Comment: 11 pages with 1 figure and 2 tables. Extensively rewritten to explain
the research bette
A Pan-Carina YSO Catalog: Intermediate-Mass Young Stellar Objects in the Carina Nebula Identified Via Mid-Infrared Excess Emission
We present a catalog of 1439 young stellar objects (YSOs) spanning the 1.42
deg^2 field surveyed by the Chandra Carina Complex Project (CCCP), which
includes the major ionizing clusters and the most active sites of ongoing star
formation within the Great Nebula in Carina. Candidate YSOs were identified via
infrared (IR) excess emission from dusty circumstellar disks and envelopes,
using data from the Spitzer Space Telescope Vela--Carina survey and the
Two-Micron All Sky Survey. We model the 1--24 /mu m IR spectral energy
distributions of the YSOs to constrain physical properties. Our Pan-Carina YSO
Catalog (PCYC) is dominated by intermediate-mass (2 Msun < m < 10 Msun) objects
with disks, including Herbig Ae/Be stars and their less evolved progenitors.
The PCYC provides a valuable complementary dataset to the CCCP X-ray source
catalogs, identifying 1029 YSOs in Carina with no X-ray detection. We also
catalog 410 YSOs with X-ray counterparts, including 62 candidate protostars.
Candidate protostars with X-ray detections tend to be more evolved than those
without. In most cases, X-ray emission apparently originating from
intermediate-mass, disk-dominated YSOs is consistent with the presence of
low-mass companions, but we also find that X-ray emission correlates with
cooler stellar photospheres and higher disk masses. We suggest that
intermediate-mass YSOs produce X-rays during their early pre-main sequence
evolution, perhaps driven by magnetic dynamo activity during the convective
atmosphere phase, but this emission dies off as the stars approach the main
sequence. Extrapolating over the stellar initial mass function scaled to the
PCYC population, we predict a total population of >2x10^4 YSOs and a
present-day star formation rate (SFR) of >0.008 Msun/yr. The global SFR in the
Carina Nebula, averaged over the past ~5 Myr, has been approximately constant.Comment: 23 pages, 11 figures, accepted for the ApJS Special Issue on the
Chandra Carina Complex Project (CCCP), scheduled for publication in May 2011.
All 16 CCCP Special Issue papers, including a version of this article with
high-quality figures and full electronic tables, are available at
http://cochise.astro.psu.edu/Carina_public/special_issue.html (through 2011
at least
Pre-main sequence stars with disks in the Eagle Nebula observed in scattered light
NGC6611 and its parental cloud, the Eagle Nebula (M16), are well-studied
star-forming regions, thanks to their large content of both OB stars and stars
with disks and the observed ongoing star formation. We identified 834
disk-bearing stars associated with the cloud, after detecting their excesses in
NIR bands from J band to 8.0 micron. In this paper, we study in detail the
nature of a subsample of disk-bearing stars that show peculiar characteristics.
They appear older than the other members in the V vs. V-I diagram, and/or they
have one or more IRAC colors at pure photospheric values, despite showing NIR
excesses, when optical and infrared colors are compared. We confirm the
membership of these stars to M16 by a spectroscopic analysis. The physical
properties of these stars with disks are studied by comparing their spectral
energy distributions (SEDs) with the SEDs predicted by models of T-Tauri stars
with disks and envelopes. We show that the age of these stars estimated from
the V vs. V-I diagram is unreliable since their V-I colors are altered by the
light scattered by the disk into the line of sight. Only in a few cases their
SEDs are compatible with models with excesses in V band caused by optical
veiling. Candidate members with disks and photospheric IRAC colors are selected
by the used NIR disk diagnostic, which is sensitive to moderate excesses, such
as those produced by disks with low masses. In 1/3 of these cases, scattering
of stellar flux by the disks can also be invoked. The photospheric light
scattered by the disk grains into the line of sight can affect the derivation
of physical parameters of ClassII stars from photometric optical and NIR data.
Besides, the disks diagnostic we defined are useful for selecting stars with
disks, even those with moderate excesses or whose optical colors are altered by
veiling or photospheric scattered light.Comment: Accepted for publication in A&
Toward dynamic pain expressions in avatars : perceived realism and pain level of diffrent action unit orders
The facial expression of pain can be decomposed in three sets of Action Units (AUs), the smallest discriminating facial movements: Brow lowering (B), Nose wrinkling + Upper lip raising (N), and Orbit tightening + Eyelid closure (O). This study compared the perception of realism and pain level from different onset orders of AUs in avatars. Seven videos of facial expressions of pain were created with four different avatars (2 women): six sequential onsets combining the three sets of AUs and one synchronized onset. 45 healthy adults (22 women; aged 23.6 ± 5.2 years) rated the realism of facial movements, and the level of intensity and unpleasantness of perceived pain. A more realistic expression was associated with the onset of O before or at the same time as N, a more intense expression was associated when B occurred last, and a higher level of unpleasantness was associated with the onset of N before B. Therefore, the sequence ONB yielded the highest ratings on both measures of realism and pain levels. These findings describe the perceived content of different orders of facial movements that could contribute to the creation of realistic pain-expressing virtual agents designed to study human-computer interactions
Candidate Coronagraphic Detections of Protoplanetary Disks around Four Young Stars
We present potential detections of H-band scattered light emission around
four young star, selected from a total sample of 45 young stars observed with
the CIAO coronagraph of the Subaru telescope. Two CTTS, CI Tau and DI Cep, and
two WTTS, LkCa 14 and RXJ 0338.3+1020 were detected. In all four cases, the
extended emission is within the area of the residual PSF halo, and is revealed
only through careful data reduction. We compare the observed extended emission
with simulations of the scattered light emission, to evaluate the plausibility
and nature of the detected emission.Comment: 9 Figures, 40 page
The pre-ZAMS nature of Mol160/IRAS23385+6053 confirmed by Spitzer
Determining the timeline for the formation of massive YSOs requires the
identification and characterisation of all the phases that a massive forming
YSO undergoes. It is of particular interest to verify the observability of the
phase in which the object is rapidly accreting while not yet igniting the
fusion of hydrogen that marks the arrival on the ZAMS. One of the candidate
prototypical objects for this phase is Mol160/IRAS23385+6053, which previous
studies suggest it could be in a pre-Hot Core stage. We further investigate
this issue by means of Spitzer imaging and spectroscopy in the 5-70 micron
range. The dense core of Mol160/IRAS23385+6053, which up to now had only been
detected at submm and mm wavelenghts has been revealed for the first time at 24
and 70 micron by Spitzer. The complete 24 micron -3.4 mm continuum cannot be
fitted with a standard model of a Zero-Age Main-Sequence (ZAMS) star embedded
in an envelope. A simple greybody fit yields a mass of 220 solar masses. The
luminosity is slightly in excess of 3000 solar luminosities, which is a factor
of 5 less than previous estimates when only IRAS fluxes were available between
20 and 100 micron. The source is under-luminous by the same factor with respect
to UCHII regions or Hot-Cores of similar circumstellar mass, and simple models
show that this is compatible with an earlier evolutionary stage. Spectroscopy
between 5 and 40 microns revelas typical PDR/PIR conditions, where the required
UV illumination may be provided by other sources revealed at 24 microns in the
same region, and which can be plausibly modeled as moderately embedded
intermediate-mass ZAMS stars. Our results strengthen the suggestion that the
central core in Mol160/IRAS23385+6053 is a massive YSO actively accreting from
its circumstellar envelope and which did not yet begin hydrogen fusion.Comment: Accepted by A&
Disk and Envelope Structure in Class 0 Protostars: I. The Resolved Massive Disk in Serpens FIRS 1
We present the first results of a program to characterize the disk and
envelope structure of typical Class 0 protostars in nearby low-mass star
forming regions. We use Spitzer IRS mid-infrared spectra, high resolution CARMA
230 GHz continuum imaging, and 2-D radiative transfer models to constrain the
envelope structure, as well as the size and mass of the circum-protostellar
disk in Serpens FIRS 1. The primary envelope parameters (centrifugal radius,
outer radius, outflow opening angle, and inclination) are well constrained by
the spectral energy distribution (SED), including Spitzer IRAC and MIPS
photometry, IRS spectra, and 1.1 mm Bolocam photometry. These together with the
excellent uv-coverage (4.5-500 klam) of multiple antenna configurations with
CARMA allow for a robust separation of the envelope and a resolved disk. The
SED of Serpens FIRS 1 is best fit by an envelope with the density profile of a
rotating, collapsing spheroid with an inner (centrifugal) radius of
approximately 600 AU, and the millimeter data by a large resolved disk with
Mdisk~1.0 Msun and Rdisk~300 AU. These results suggest that large, massive
disks can be present early in the main accretion phase. Results for the larger,
unbiased sample of Class~0 sources in the Perseus, Serpens, and Ophiuchus
molecular clouds are needed to determine if relatively massive disks are
typical in the Class 0 stage.Comment: Comments: 13 pages, 8 figures, 3 tables; accepted for publication in
the Ap
The Choices, Challenges, and Lessons Learned from a Multi-Method Social-Emotional / Character Assessment in and Out of School Time Setting
Out-of-School-Time (OST) programs are increasingly recognized as a venue to actively engage children and youth in character development activities, but little guidance exists as to how to assess individual children and youth in OST environments for the sake of evaluating their character development. This research brief uses an illustrative case study to reflect upon the experience of selecting and completing a strength-based, multi-modal social-emotional / character assessment that used a direct assessment and a multiple informant behavior rating scale in an OST setting. Insights derived from the case study reveal opportunities and challenges associated with each assessment modality. This paper shares lessons learned with those conducting individual assessments in OST environments and with those seeking to improve our capacity to complete screening, formative, and summative assessments of social-emotional and character constructs in OST youth development programs to help children
- …