- ID:
- ivo://CDS.VizieR/J/A+A/350/883
- Title:
- R CrA ISOCAM observations
- Short Name:
- J/A+A/350/883
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of an ISOCAM survey of the R CrA star formation region are presented. The survey was carried out in two broad-band filters, LW2 (5-8.5{mu}m) and LW3 (12-18{mu}m). Although it was not possible to map the densest, central region due to saturation problems, 21 sources were identified which showed mid-IR excesses. Most of these sources have not previously been recognised as YSOs (Young Stellar Objects), mainly because they are relatively faint. We find evidence for a population of very low mass stars which are probably brown dwarfs in their early contraction phases.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/367/1609
- Title:
- RCW 106 Giant Molecular Cloud 13CO mapping
- Short Name:
- J/MNRAS/367/1609
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first paper in a series detailing the results of ^13^CO observations of a ~1{deg}^2^ region of the giant molecular cloud (GMC) complex associated with the HII region RCW 106. The ^13^CO observations are also the first stage of a multi-molecular line study of the same region. These observations were amongst the first made using the new on-the-fly mapping capability of the Australia Telescope National Facility Mopra Telescope. In the configuration used, the instrument provided a full width at half-maximum (FWHM) beam size of 33arcsec and a velocity resolution of 0.17km/s. The gas emission takes the form of a string of knots, oriented along an axis that extends from the north-west (NW) to the south-east (SE) of the field of the observations, and which is surrounded by a more extended, diffuse emission. We analyse the 2D integrated ^13^CO emission using the CLUMPFIND algorithm and identify 61 clumps. We compare the gas data in the GMC with the dust data provided by 21um Midcourse Space Experiment (MSX) and 1.2mm Swedish European Southern Observatory Submillimetre Telescope (SEST) images that we both regridded to the cell spacing of the Mopra data and smoothed to the same resolution.
- ID:
- ivo://CDS.VizieR/J/ApJ/870/115
- Title:
- Reddening, distance modulus & Fe/H of RRLs in w Cen
- Short Name:
- J/ApJ/870/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We developed a new approach to provide accurate estimates of the metal content, reddening, and true distance modulus of RR Lyrae stars (RRLs). The method is based on homogeneous optical (BVI) and near-infrared (JHK) mean magnitudes and on predicted period-luminosity-metallicity relations (IJHK) and absolute mean magnitude-metallicity relations (BV). We obtained solutions for three different RRL samples in {omega}Cen: first overtone (RRc, 90), fundamental (RRab, 80), and global (RRc+RRab) in which the period of first overtones were fundamentalized. The metallicity distribution shows a well defined peak at [Fe/H]~-1.98 and a standard deviation of {sigma}=0.54dex. The spread is, as expected, metal-poor ([Fe/H]<=-2.3) objects. The current metallicity distribution is ~0.3dex more metal-poor than similar estimates for RRLs available in the literature. The difference vanishes if the true distance modulus we estimated is offset by -0.06/-0.07mag in true distance modulus. We also found a cluster true distance modulus of {mu}=13.720{+/-}0.002{+/-}0.030mag, where the former error is the error on the mean and the latter is the standard deviation. Moreover, we found a cluster reddening of E(B-V)=0.132{+/-}0.002{+/-}0.028mag and spatial variations of the order of a few arcmin across the body of the cluster. Both the true distance modulus and the reddening are slightly larger than similar estimates available in the literature, but the difference is within 1{sigma}. The metallicity dependence of distance diagnostics agrees with theory and observations, but firm constraints require accurate and homogeneous spectroscopic measurements.
- ID:
- ivo://CDS.VizieR/J/MNRAS/410/1237
- Title:
- Red MSX survey (RMS) massive young stars
- Short Name:
- J/MNRAS/410/1237
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Red MSX Source (RMS) survey has identified a large sample of massive young stellar objects and ultra compact HII regions from a sample of ~2000 MSX and Two Micron All Sky Survey (2MASS) colour selected sources. Using a recent catalogue of molecular clouds derived from the Boston University-Five College Radio Astronomy Observatory (BU-FCRAO) Galactic Ring Survey (GRS), and by applying a Galactic scaleheight cut-off of 120pc, we solve the distance ambiguity for RMS sources located within 18{deg}<|l|>54{deg}. These two steps yield kinematic distances to 291 sources out of a possible 326, located within the GRS longitude range. Combining distances and integrated fluxes derived from spectral energy distributions, we estimate luminosities to these sources and find that >90 per cent are indicative of the presence of a massive star. We find the completeness limit of our sample is ~10^4^L_{sun}_, which corresponds to a zero-age main-sequence star with a mass of ~12M_{sun}_. Selecting only these sources, we construct a complete sample of 196 sources.
- ID:
- ivo://CDS.VizieR/J/MNRAS/418/1689
- Title:
- Red MSX water maser and ammonia emissions
- Short Name:
- J/MNRAS/418/1689
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Red MSX Source (RMS) survey has identified a sample of ~1200 massive young stellar objects (MYSOs), compact and ultra-compact HII regions from a sample of ~2000 MSX and Two Micron All Sky Survey (2MASS) colour-selected sources. We have used the 100-m Green Bank Telescope to search for 22-24GHz water maser and ammonia (1,1), (2,2) and (3,3) emission towards ~600 RMS sources located within the northern Galactic plane. We have identified 308 H_2_O masers which corresponds to an overall detection rate of ~50 per cent. We find no significant difference in the detection rate for HII regions and MYSOs which would suggest that the conditions required to produce maser emission are equally likely in both phases. Comparing the detection rates as a function of luminosity, we find the H_2_O detection rate has a positive dependence on the source luminosity, with the detection rate increasing with increasing luminosity.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A175
- Title:
- Red supergiant stars in the LMC. II.
- Short Name:
- J/A+A/616/A175
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The characteristics of infrared properties and mid-infrared (MIR) variability of red supergiant (RSG) stars in the Large Magellanic Cloud (LMC) are analyzed based on 12 bands of near-infrared (NIR) to MIR co-added data from 2MASS, Spitzer and WISE, and ~6.6 years of MIR time-series data collected by the ALLWISE and NEOWISE-R projects. 773 RSGs candidates are compiled from the literature and verified by using the color-magnitude diagram (CMD), spectral energy distribution (SED) and MIR variability. About 15% of valid targets in the IRAC1-IRAC2/IRAC2-IRAC3 diagram may show Polycyclic Aromatic Hydrocarbon (PAH) emission. We show that arbitrary dereddening Q parameters related to the IRAC4, S9W, WISE3, WISE4 and MIPS24 bands could be constructed based on a precise measurement of MIR interstellar extinction law. Several peculiar outliers in our sample are discussed, in which one outlier might be a RSG right before the explosion or an extreme asymptotic giant branch (AGB) star in the very late evolutionary stage based on the MIR spectrum and photometry. There are 744 identified RSGs in the final sample having both the WISE1- and WISE2-band time-series data. The results show that the MIR variability is increasing along with the increasing of brightness. There is a relatively tight correlation between the MIR variability, mass loss rate (MLR; in terms of K_S-WISE3 color) and the warm dust/continuum (in terms of WISE4 magnitude/flux), where the MIR variability is evident for the targets with K_S-WISE3>1.0mag and WISE4<6.5mag, while the rest of the targets show much smaller MIR variability. The MIR variability is also correlated with the MLR for which targets with larger variability also show larger MLR with an approximate upper limit of -6.1M_{sun}_/yr. The variability and luminosity may both be important for the MLR since the WISE4-band flux is increasing exponentially along with the degeneracy of luminosity and variability. The identified RSG sample has been compared with the theoretical evolutionary models and shown that the discrepancy between observation and evolutionary models can be mitigated by considering both variability and extinction.
- ID:
- ivo://CDS.VizieR/J/A+A/577/A18
- Title:
- Reduced CRIRES spectra around S multiplet 3
- Short Name:
- J/A+A/577/A18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sulphur is an important, volatile alpha element but its role in the Galactic chemical evolution is still uncertain. We derive the S abundances in RGB stars in three Galactic globular clusters (GC) that cover a wide metallicity range (-2.3<[Fe/H]<-1.2): M4, M22, and M30. The halo field stars show a large scatter in the [S/Fe] ratio in this metallicity span, which is inconsistent with canonical chemical evolution models. To date, very few measurements of [S/Fe] exist for stars in GCs, which are good tracers of the chemical enrichment of their environment. However, some light and alpha elements show star-to-star variations within individual GCs and it is yet unclear whether sulphur also varies between GC stars. We used the the infrared spectrograph CRIRES to obtain high-resolution (R~50000), high signal-to-noise (SNR~200 per px) spectra in the region of the SI multiplet 3 at 1045nm for 15 GC stars selected from the literature (6 stars in M4, 6 stars in M22 and 3 stars in M30). Multiplet 3 is better suited for S abundance derivation than the more commonly used lines of multiplet 1 at 920nm, since its lines are not blended by telluric absorption or other stellar features at low metallicity. We used spectral synthesis to derive the [S/Fe] ratio of the stars assuming local thermodynamic equilibrium (LTE). We find mean [S/Fe]=0.58+/-0.01+/-0.20dex (statistical and systematic error) for M4, [S/Fe]=0.57+/-0.01+/-0.19dex for M22, and [S/Fe]=0.55+/-0.02+/-0.16dex for M30. The negative NLTE corrections are estimated to be in the order of the systematic uncertainties. With the tentative exception of two stars with measured high S abundances, we conclude that sulphur behaves like a typical alpha element in the studied Galactic GCs, showing enhanced abundances with respect to the solar value at metallicities below [Fe/H]=-1.0dex without a considerable spread.
- ID:
- ivo://CDS.VizieR/J/A+A/629/A131
- Title:
- Reduced X-shooter spectra of GRB 190114A
- Short Name:
- J/A+A/629/A131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detections of molecular hydrogen (H_2_), vibrationally-excited H_2_ (H_2_*), and neutral atomic carbon (CI), an efficient tracer of molecular gas, in two new afterglow spectra of GRBs 181020A (z=2.938) and 190114A (z=3.376), observed with X-shooter at the Very Large Telescope (VLT). Both host-galaxy absorption systems are characterized by strong damped Lyman-alpha absorbers (DLAs) and substantial amounts of molecular hydrogen with logN(HI,H_2_)=22.20+/-0.05, 20.40+/-0.04 (GRB 181020A) and logN(HI, H_2_)=22.15+/-0.05, 19.44+/-0.04 (GRB 190114A). The DLA metallicites, depletion levels, and dust extinctions are within the typical regimes probed by GRBs with [Zn/H]=-1.57+/-0.06, [Zn/Fe]=0.67+/-0.03, and AV=0.27+/-0.02mag (GRB 181020A) and [Zn/H]=-1.23+/-0.07, [Zn/Fe]=1.06+/-0.08, and AV=0.36+/-0.02mag (GRB 190114A). In addition, we examine the molecular gas content of all known H2-bearing GRB-DLAs and explore the physical conditions and characteristics required to simultaneously probe CI and H_2_*. We confirm that H2 is detected in all CI- and H2*-bearing GRB absorption systems, but that these rarer features are not necessarily detected in all GRB H2 absorbers. We find that a large molecular fraction of f_H2_>~10^-3^ is required for CI to be detected. The defining characteristic for H_2_* to be present is less clear, though a large H_2_ column density is an essential factor. We also find that the observed line profiles of the molecular-gas tracers are kinematically "cold", with small velocity offsets of {delta}v<20km/s from the bulk of the neutral absorbing gas. We then derive the H_2_ excitation temperatures of the molecular gas and find that they are relatively low with Tex~=100-300K, however, there could be evidence of warmer components populating the high-J H_2_ levels in GRBs 181020A and 190114A. Finally, we demonstrate that even though the X-shooter GRB afterglow campaign has been successful in recovering several H2-bearing GRB-host absorbers, this sample is still hampered by a significant dust bias excluding the most dust-obscured H_2_ absorbers from identification. CI and H_2_* could open a potential route to identify molecular gas even in low-metallicity or highly dust-obscured bursts, though they are only efficient tracers for the most H2-rich GRB-host absorption systems.
- ID:
- ivo://CDS.VizieR/J/A+A/553/A81
- Title:
- Refraction of corundum, spinel, {alpha}-quartz
- Short Name:
- J/A+A/553/A81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Many cosmic dust species, among them refractory oxides, form at temperatures higher than 300K. Nevertheless, most astrophysical studies are based on the room-temperature optical constants of solids, such as corundum and spinel. A more realistic approach is needed for these materials, especially in the context of modeling late-type stars. We aimed at deriving sets of optical constants of selected, astrophysically relevant oxide dust species with high melting points. A high-temperature, high-pressure cell and a Fourier-transform spectrometer were used to measure reflectance spectra of polished samples. For corundum ({alpha}-Al_2_O_3_), spinel (MgAl_2_O_4_), and {alpha}-quartz (SiO_2_), temperature-dependent optical constants were measured from 300K up to more than 900K. Small particle spectra were also calculated from these data.
- ID:
- ivo://CDS.VizieR/J/A+A/483/661
- Title:
- Refractive index for silicon carbide (SiC)
- Short Name:
- J/A+A/483/661
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The SiC optical constants are fundamental inputs for radiative transfer (RT) models of astrophysical dust environments. However, previously published values contain errors and do not adequately represent the bulk physical properties of the cubic ({beta}) SiC polytype usually found around carbon stars. We provide new, uncompromised optical constants for {beta}- and {alpha}-SiC derived from single-crystal reflectance spectra and investigate quantitatively (i) whether there is any difference between {alpha}- and {beta}-SiC that can be seen in infrared (IR) spectra and optical functions and (ii) whether weak features from {lambda}~12.5-13.0{mu}m need to be fitted. We measured mid- and far-IR reflectance spectra for two samples of 3C ({beta}-)SiC and four samples of 6H ({alpha}-)SiC. For the latter group, we acquired polarized data (E{perpendicular.to}c, E{parallel.to}c orientations). We calculated the real and imaginary parts of the complex refractive index (n({lambda})+ik({lambda})) and the ideal absorption coefficients via classical dispersion fits to our reflectance spectra.
