707 research outputs found
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
Far infrared mapping of three Galactic star forming regions : W3(OH), S 209 & S 187
Three Galactic star forming regions associated with W3(OH), S209 and S187
have been simultaneously mapped in two trans-IRAS far infrared (FIR) bands
centered at ~ 140 and 200 micron using the TIFR 100 cm balloon borne FIR
telescope. These maps show extended FIR emission with structures. The HIRES
processed IRAS maps of these regions at 12, 25, 60 & 100 micron have also been
presented for comparison. Point-like sources have been extracted from the
longest waveband TIFR maps and searched for associations in the other five
bands. The diffuse emission from these regions have been quantified, which
turns out to be a significant fraction of the total emission. The spatial
distribution of cold dust (T < 30 K) for two of these sources (W3(OH) & S209),
has been determined reliably from the maps in TIFR bands. The dust temperature
and optical depth maps show complex morphology. In general the dust around S209
has been found to be warmer than that in W3(OH) region.Comment: Accepted for publication in Journal of Astrophysics and Astronomy (20
pages including 8 figures & 3 tables
High-Mass Cloud Cores in the eta Carinae Giant Molecular Cloud
We carried out an unbiased survey for massive dense cores in the giant
molecular cloud associated with eta Carinae with the NANTEN telescope in 12CO,
13CO, and C18O 1-0 emission lines. We identified 15 C18O cores. Two of the 15
cores are associated with IRAS point sources whose luminosities are larger than
10^4 Lo, which indicates that massive star formation is occuring within these
cores. Five cores including the two with IRAS sources are associated with MSX
point sources. We detected H13CO+ (1-0) emission toward 4 C18O cores, one of
which is associated with neither IRAS nor MSX point sources. This core shows
the presence of a bipolar molecular outflow in 12CO (2-1), which indicates that
star formation is also occuring in the core. In total, six C18O cores out of 15
are experienced star formation, and at least 2 of 15 are massive-star forming
cores in the eta Car GMC. We found that massive star formation occurs
preferentially in cores with larger column density, mass, number density, and
smaller ratio of virial mass to LTE mass Mvir/M. We also found that the cores
in the eta Car GMC are characterized by large line width and Mvir/M on average
compared to the cores in other GMCs. We investigated the origin of a large
amount of turbulence in the eta Car GMC. We propose the possibility that the
large turbulence was pre-existing when the GMC was formed, and is now
dissipating. Mechanisms such as multiple supernova explosions in the Carina
flare supershell may have contributed to form a GMC with a large amount of
turbulence.Comment: 41 pages, including 11 fugures and 9 tables. Accepted by ApJ. Author
changed. Paper with high resolution figures is available at
http://astrol.cias.osakafu-u.ac.jp/~yonekura/work/paper/etaCar
Pulmonary Arterial Pressure Management Based on Oral Medicine for Pediatric Living Donor Liver Transplant With Portopulmonary Hypertension
Ueno T., Hiwatashi S., Saka R., et al. Pulmonary Arterial Pressure Management Based on Oral Medicine for Pediatric Living Donor Liver Transplant With Portopulmonary Hypertension. Transplantation Proceedings 50, 2614 (2018); https://doi.org/10.1016/J.TRANSPROCEED.2018.03.068.Pediatric living donor liver transplantation (LDLT) in patients with advanced portopulmonary hypertension (PoPH) is associated with poor prognoses. Recently, novel oral medications, including endothelin receptor antagonists (ERAs), phosphodiesterase 5 (PDE5) inhibitors, and oral prostacyclin (PGI2) have been used to treat PoPH. Pediatric patients with PoPH who underwent LDLT from 2006 to 2016 were enrolled. Oral pulmonary hypertension (PH) medication was administered to control pulmonary arterial pressure (PAP). Four patients had PoPH. Their ages ranged from 6 to 16 years, and their original diseases were biliary atresia (n = 2), portal vein obstruction (n = 1), and intrahepatic portal systemic shunt (n = 1). For preoperative management, 2 patients received continuous intravenous PGI2 and 2 oral medications (an ERA alone or an ERA and a PDE5 inhibitor), and 2 received only oral drugs (an ERA and a PDE5 inhibitor). One patient managed only with intravenous PGI2 died. In the remaining 3 cases, intravenous PGI2 or NO was discontinued before the end of the first postoperative week. Postoperative medications were oral PGI2 alone (n = 1), an ERA alone (n = 1), or the combination of an ERA and a PDE5 inhibitor (n = 1). An ERA was the first-line therapy, and a PDE5 inhibitor was added if there was no effect. New oral PH medications were effective and safe for use in pediatric patients following LDLT. In particular, these new oral drugs prevent the need for central catheter access to infuse PGI2
Candidate X-ray-Emitting OB Stars in the Carina Nebula Identified Via Infrared Spectral Energy Distributions
We report the results of a new survey of massive, OB stars throughout the
Carina Nebula using the X-ray point source catalog provided by the Chandra
Carina Complex Project (CCCP) in conjunction with infrared (IR) photometry from
the Two Micron All-Sky Survey and the Spitzer Space Telescope Vela--Carina
survey. Mid-IR photometry is relatively unaffected by extinction, hence it
provides strong constraints on the luminosities of OB stars, assuming that
their association with the Carina Nebula, and hence their distance, is
confirmed. We fit model stellar atmospheres to the optical (UBV) and IR
spectral energy distributions (SEDs) of 182 OB stars with known spectral types
and measure the bolometric luminosity and extinction for each star. We find
that the extinction law measured toward the OB stars has two components:
Av=1--1.5 mag produced by foreground dust with a ratio of total-to-selective
absorption Rv=3.1 plus a contribution from local dust with Rv>4.0 in the Carina
molecular clouds that increases as Av increases. Using X-ray emission as a
strong indicator of association with Carina, we identify 94 candidate OB stars
with Lbol\geq10^4 Lsun by fitting their IR SEDs. If the candidate OB stars are
eventually confirmed by follow-up spectroscopic observations, the number of
cataloged OB stars in the Carina Nebula will increase by ~50%. Correcting for
incompleteness due to OB stars falling below the Lbol cutoff or the CCCP
detection limit, these results potentially double the size of the young massive
stellar population.Comment: 19 pages, 8 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, are available at
http://cochise.astro.psu.edu/Carina_public/special_issue.html (through 2011
at least
Multifractal Scaling, Geometrical Diversity, and Hierarchical Structure in the Cool Interstellar Medium
Multifractal scaling (MFS) refers to structures that can be described as a
collection of interwoven fractal subsets which exhibit power-law spatial
scaling behavior with a range of scaling exponents (concentration, or
singularity, strengths) and dimensions. The existence of MFS implies an
underlying multiplicative (or hierarchical, or cascade) process. Panoramic
column density images of several nearby star- forming cloud complexes,
constructed from IRAS data and justified in an appendix, are shown to exhibit
such multifractal scaling, which we interpret as indirect but quantitative
evidence for nested hierarchical structure. The relation between the dimensions
of the subsets and their concentration strengths (the "multifractal spectrum'')
appears to satisfactorily order the observed regions in terms of the mixture of
geometries present: strong point-like concentrations, line- like filaments or
fronts, and space-filling diffuse structures. This multifractal spectrum is a
global property of the regions studied, and does not rely on any operational
definition of "clouds.'' The range of forms of the multifractal spectrum among
the regions studied implies that the column density structures do not form a
universality class, in contrast to indications for velocity and passive scalar
fields in incompressible turbulence, providing another indication that the
physics of highly compressible interstellar gas dynamics differs fundamentally
from incompressible turbulence. (Abstract truncated)Comment: 27 pages, (LaTeX), 13 figures, 1 table, submitted to Astrophysical
Journa
New young planetary nebulae in IPHAS
Original article can be found at: http://www.aanda.org/ Copyright The European Southern Observatory. DOI: 10.1051/0004-6361/200811575Aims. We search for very small-diameter galactic planetary nebulae (PNe) representing the earliest phases of PN evolution. The IPHAS catalogue of H-emitting stars provides a useful basis for this study since all sources present in this catalogue must be of small angular diameter. Methods. The PN candidates are selected based on their location in two colour-colour diagrams: IPHAS (r' - H) vs. (r' - i'), and 2MASS (J - H) vs. (H - ). Spectroscopic follow-up was carried out on a sample of candidates to confirm their nature. Results. We present a total of 83 PN candidates. We were able to obtain spectra or find the classification from the literature for 35 candidates. Five of these objects are likely to be new PNe, including one large bipolar PN discovered serendipitously close to an emission-line star. PN distances deduced from extinction-distance relations based on IPHAS field-star photometry are presented for the first time. These yield distance estimates for our objects in the range 2 kpc and 6 kpc. From the data in hand, we conclude that four of the discovered objects are probably young PNe.Peer reviewe
Phenomenological Aspects of Gauge Mediation with Sequestered Supersymmetry Breaking in light of Dark Matter Detection
In a recent work, a model of gauge mediation with sequestered supersymmetry
(SUSY) breaking was proposed. In this model, the mass of the gravitino is
O(100) GeV without causing the flavor-changing neutral-current problem. In
contrast to traditional gauge mediation, the gravitino is not the lightest SUSY
particle and the neutralino is the candidate of the dark matter. In this paper,
we investigate phenomenological aspects of this model and discuss the
possibility of the direct detection of the dark matter. In particular, we focus
on the light neutralino case and find that the light-Higgsino scenario such as
the focus point is interesting, taking account of the recent CDMS result.Comment: 17 pages, 8 figures; v2:references added, some corrections;
v3:version accepted for publication in JHE
Photon Dominated Regions in NGC 3603
Aims: We aim at deriving the excitation conditions of the interstellar gas as
well as the local FUV intensities in the molecular cloud surrounding NGC 3603
to get a coherent picture of how the gas is energized by the central stars.
Methods: The NANTEN2-4m submillimeter antenna is used to map the [CI] 1-0, 2-1
and CO 4-3, 7-6 lines in a 2' x 2' region around the young OB cluster NGC 3603
YC. These data are combined with C18O 2-1 data, HIRES-processed IRAS 60 and 100
micron maps of the FIR continuum, and Spitzer/IRAC maps. Results: The NANTEN2
observations show the presence of two molecular clumps located south-east and
south-west of the cluster and confirm the overall structure already found by
previous CS and C18O observations. We find a slight position offset of the peak
intensity of CO and [CI], and the atomic carbon appears to be further extended
compared to the molecular material. We used the HIRES far-infrared dust data to
derive a map of the FUV field heating the dust. We constrain the FUV field to
values of \chi = 3 - 6 \times 10^3 in units of the Draine field across the
clouds. Approximately 0.2 to 0.3 % of the total FUV energy is re-emitted in the
[CII] 158 {\mu}m cooling line observed by ISO. Applying LTE and escape
probability calculations, we derive temperatures (TMM1 = 43 K, TMM2 = 47 K),
column densities (N(MM1) = 0.9 \times 10^22 cm^-2, N(MM2) = 2.5 \times 10^22
cm^-2) and densities (n(MM1) = 3 \times 10^3 cm^-3, n(MM2) = 10^3 -10^4 cm^-3)
for the two observed molecular clumps MM1 and MM2. Conclusions: The cluster is
strongly interacting with the ambient molecular cloud, governing its structure
and physical conditions. A stability analysis shows the existence of
gravitationally collapsing gas clumps which should lead to star formation.
Embedded IR sources have already been observed in the outskirts of the
molecular cloud and seem to support our conclusions.Comment: 13 pages, 10 figures, accepted for publication by A&
Higgs Boson Mass in Low Scale Gauge Mediation Models
We consider low scale gauge mediation models with a very light gravitino
m_{3/2}~16 eV, in the light of recent experimental hints on the Higgs boson
mass. The light gravitino is very interesting since there is no gravitino
over-production problem, but it seems difficult to explain the Higgs boson mass
of ~125 GeV. This is because of the conflict between the light gravitino mass
and heavy SUSY particle masses needed for producing the relatively heavy Higgs
boson mass. We consider two possible extensions in this paper: a singlet
extension of the Higgs sector, and strongly coupled gauge mediation. We show
that there is a large parameter space, in both scenarios, where the Higgs boson
mass of ~125 GeV is explained without any conflict with such a very light
gravitino.Comment: 23 pages, 5 figure
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