- ID:
- ivo://CDS.VizieR/J/A+A/657/A70
- Title:
- Linking high- and low-mass star formation
- Short Name:
- J/A+A/657/A70
- Date:
- 21 Mar 2022 09:28:51
- Publisher:
- CDS
- Description:
- Astronomers have yet to establish whether high-mass protostars form from high-mass prestellar cores, similar to their lower-mass counterparts, or from lower-mass fragments at the heart of a pre-protostellar cluster undergoing large-scale collapse. Part of the uncertainty is due to a shortage of envelope structure data on protostars of a few tens of solar masses, where we expect to see a transition from intermediate-mass star formation to the high-mass process. We sought to derive the masses, luminosities, and envelope density profiles for eight sources in Cygnus-X, whose mass estimates in the literature placed them in the sampling gap. Combining these sources with similarly evolved sources in the literature enabled us to perform a meta-analysis of protostellar envelope parameters over six decades in source luminosity. We performed spectral energy distribution (SED) fitting on archival broadband photometric continuum data from 1.2 to 850 microns, to derive bolometric luminosities for our eight sources plus initial mass and radius estimates for modelling density and temperature profiles with the radiative transfer package Transphere. The envelope masses, densities at 1000AU, outer envelope radii, and density power law indices as functions of bolometric luminosity all follow established trends in the literature spanning six decades in luminosity. Most of our sources occupy an intermediate to moderately high range of masses and luminosities, which helps more firmly establish the continuity between low- and high-mass star formation mechanisms. Our density power law indices are consistent with observed values in literature, which show no discernible trends with luminosity. Finally, we show that the trends in all of the envelope parameters for high-mass protostars are statistically indistinguishable from trends in the same variables for low- and intermediate-mass protostars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/475/915
- Title:
- L1489IRS observed by the submillimeter array
- Short Name:
- J/A+A/475/915
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Submillimeter Array observations of the Young Stellar Object L1489IRS (IRAS 04016+2610). These include images of the continuum at 267 GHz (1.12 mm) and line emission of the HCO+ J=3-2 transition at 267.55762 GHz. The HCO+ image is available in two different (u,v)-weighting schemes, natural and uniform, optimizing for S/N and resolution respectively. The continuum image is only available in uniform weighting. The synthesized beam size is 1".
583. L379IRS3 radio lines
- ID:
- ivo://CDS.VizieR/J/AZh/93/409
- Title:
- L379IRS3 radio lines
- Short Name:
- J/AZh/93/409
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of spectral observations of the region of massive star formation L379IRS3 (IRAS 18265-1517) are presented. The observations were carried out with the 30-m Pico Veleta radio telescope (Spain) at seven frequencies in the 1-mm, 2-mm, and 3-mm wavelength bands. Lines of 24 molecules were detected, from simple diatomic or triatomic species to complex eight- or nine-atom compounds such as CH_3_OCHO or CH_3_OCH_3_. Rotation diagrams constructed from methanol and methyl cyanide lines were used to determine the temperature of the quiescent gas in this region, which is about 40-50K. In addition to this warm gas, there is a hot component that is revealed through high-energy lines of methanol and methyl cyanide, molecular lines arising in hot regions, and the presence of H_2_O masers and Class II methanol masers at 6.7GHz, which are also related to hot gas. One of the hot regions is probably a compact hot core, which is located near the southern submillimeter peak and is related to a group of methanol masers at 6.7GHz. High-excitation lines at other positions may be associated with other hot cores or hot post-shock gas in the lobes of bipolar outflows. The rotation diagrams can be use to determine the column densities and abundances of methanol (10^-9^) and methyl cyanide (about 10^-11^) in the quiescent gas. The column densities of A- and E-methanol in L379IRS3 are essentially the same. The column densities of other observed molecules were calculated assuming that the ratios of the molecular level abundances correspond to a temperature of 40 K. The molecular composition of the quiescent gas is close to that in another region of massive star formation, DR21(OH). The only appreciable difference is that the column density of SO2 in L379IRS3 is at least a factor of 20 lower than the value in DR21(OH). The SO_2_/CS and SO2/OCS abundance ratios, which can be used as chemical clocks, are lower in L379IRS3 than in DR21(OH), suggesting that L379IRS3 is probably younger than DR21(OH).
- ID:
- ivo://CDS.VizieR/J/A+A/462/81
- Title:
- L_IR_-T_dust_ relation in galaxies
- Short Name:
- J/A+A/462/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IRAS observations show the existence of a correlation between the infrared luminosity L_IR_ and dust temperature T_d_ in star-forming galaxies, in which larger L_IR_ leads to higher dust temperature. The L_IR_-T_d_ relation is commonly seen as reflecting the increase in dust temperature in galaxies with higher star formation rate (SFR). Even though the correlation shows a significant amount of dispersion, a unique relation has been commonly used to construct spectral energy distributions (SEDs) of galaxies in distant universe studies, such as source number counting or photometric redshift determination. In this work, we introduce a new parameter, namely the size of the star-forming region r_IR_ and lay out the empirical and modelled relation between the global parameters L_IR_, T_d_ and r_IR_ of IR-bright non-AGN galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/420/945
- Title:
- L1551 ISOCAM observations
- Short Name:
- J/A+A/420/945
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a deep mid-IR ISOCAM survey of the L1551 dark molecular cloud are presented. The aim of this survey is a search for new YSO (Young Stellar Object) candidates, using two broad-band filters centred at 6.7 and 14.3{mu}m. Although two regions close to the centre of L1551 had to be avoided due to saturation problems, 96 sources were detected in total (76 sources at 6.7{mu}m and 44 sources at 14.3{mu}m). Using the 24 sources detected in both filters, 14 were found to have intrinsic mid-IR excess at 14.3{mu}m and were therefore classified as YSO candidates. Using additional observations in B, V, I, J, H and K obtained from the ground, most candidates detected at these wavelengths were confirmed to have mid-IR excess at 6.7{mu}m as well, and three additional YSO candidates were found.
- ID:
- ivo://CDS.VizieR/J/ApJ/348/98
- Title:
- LMC AGB stars IRAS fluxes
- Short Name:
- J/ApJ/348/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for optically obscured asymptotic giant branch (AGB) stars in the Large Magellanic Cloud (LMC), combining data obtained using the IRAS satellite with near-infrared photographic plate material of a 15deg^2^ region in the northern LMC. Of the 156 IRAS sources that are detected either in separate cross-scans or in more than one passband, 63 have [12-25] colors consistent with their being either stellar photospheres or circumstellar dust shells. Seventeen of these we identify with bright (I_c_<9) foreground stars in our own Galaxy, while a further 17 are associated with red supergiants in the LMC. Of the remaining stars, no more than five are likely to be optically visible AGB stars, while the rest have no obvious optical counterpart. This immediately rules out the presence of sufficient high-luminosity "cocoon" stars to explain the observed deficit of several hundred luminous (M_bol_<-6) AGB stars between the predictions of standard models of AGB evolution and the observed luminosity function. It remains possible that most of the unidentified sources are dusty AGB stars, evolving through a phase of enhanced mass loss toward becoming planetary nebulae. We infer bolometric magnitudes as low as M_bol_~-5 for these sources and suggest that this phase can be triggered at low luminosities, truncating AGB evolution and leading to the observed scarcity of asymptotic giant branch stars with bolometric magnitudes brighter than -6.0mag.
- ID:
- ivo://CDS.VizieR/J/AJ/137/4810
- Title:
- LMC-SAGE AGB star candidates
- Short Name:
- J/AJ/137/4810
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present empirical relations describing excess emission from evolved stars in the Large Magellanic Cloud (LMC) using data from the Spitzer Space Telescope Surveying the Agents of a Galaxy's Evolution (SAGE) survey which includes the Infrared Array Camera (IRAC) 3.6, 4.5, 5.8, and 8.0um and Multiband Imaging Photometer (MIPS) 24, 70, and 160um bands. We combine the SAGE data with the Two Micron All Sky Survey (2MASS; J, H, and Ks) and the optical Magellanic Cloud Photometric Survey (MCPS; U, B, V, and I) point source catalogs in order to create complete spectral energy distributions (SEDs) of the asymptotic giant branch (AGB) star candidates in the LMC. AGB star outflows are among the main producers of dust in a galaxy, and this mass loss results in an excess in the fluxes observed in the 8 and 24um bands. The aim of this work is to investigate the mass loss return by AGB stars to the interstellar medium of the LMC by studying the dependence of the infrared excess flux on the total luminosity.
- ID:
- ivo://CDS.VizieR/J/AJ/137/3139
- Title:
- LMC SAGE. New variable evolved stars and YSOs
- Short Name:
- J/AJ/137/3139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present initial results and source lists of variable sources in the Large Magellanic Cloud (LMC) for which we detect thermal infrared variability from the Surveying the Agents of a Galaxy's Evolution (SAGE) survey, which had two epochs of photometry separated by 3 months. The SAGE survey mapped a 7{deg}x7{deg} region of the LMC using the Infrared Array Camera (IRAC) and the MIPS instruments on board Spitzer. Variable sources are identified using a combination of the IRAC 3.6, 4.5, 5.8, 8.0um bands and the MIPS 24um bands. An error-weighted flux difference between the two epochs is used to assess the variability. Of the ~3 million sources detected at both epochs, we find ~2000 variable sources for which we provide electronic catalogs. Most of the variable sources can be classified as asymptotic giant branch (AGB) stars. A large fraction (>66%) of the extreme AGB stars are variable and only smaller fractions of carbon-rich (6.1%) and oxygen-rich (2.0%) stars are detected as variable sources. We also detect a population of variable young stellar object candidates.
- ID:
- ivo://CDS.VizieR/J/A+A/609/A114
- Title:
- Local Group AGB stars and red supergiants
- Short Name:
- J/A+A/609/A114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Mass loss is one of the fundamental properties of asymptotic giant branch (AGB) stars, and through the enrichment of the interstellar medium, AGB stars are key players in the life cycle of dust and gas in the universe. However, a quantitative understanding of the mass-loss process is still largely lacking. To investigate mass loss and luminosity in a large sample of evolved stars in several Local Group galaxies with a variety of metallicities and star-formation histories: the Small and Large Magellanic Cloud, and the Fornax, Carina, and Sculptor dwarf spheroidal galaxies (dSphs). Dust radiative transfer models are presented for 225 carbon stars and 171 oxygen-rich evolved stars in several Local Group galaxies for which spectra from the Infrared Spectrograph on Spitzer are available. The spectra are complemented with available optical and infrared photometry to construct spectral energy distributions. A minimisation procedure is used to determine luminosity and mass-loss rate (MLR). Pulsation periods are derived for a large fraction of the sample based on a re-analysis of existing data. New deep K-band photometry from the VMC survey and multi-epoch data from IRAC (at 4.5 micron) and AllWISE and NEOWISE have allowed us to derive pulsation periods longer than 1000 days for some of the most heavily obscured and reddened objects. We derive (dust) MLRs and luminosities for the entire sample. The estimated MLRs can differ significantly from estimates for the same objects in the literature due to differences in adopted optical constants (up to factors of several) and details in the radiative transfer modelling. Updated parameters for the super-AGB candidate MSX SMC 055 (IRAS 00483-7347) are presented. Its current mass is estimated to be 8.5 +- 1.6 solar mass, suggesting an initial mass well above 8 solar mass in agreement with estimates based on its large Rubidium abundance. Using synthetic photometry, we present and discuss color-color and color-magnitude diagrams which can be expected from the James Webb Space Telescope.
- ID:
- ivo://CDS.VizieR/J/ApJ/615/887
- Title:
- Localization of SGR 1627-41 and AXP 1E1841-045
- Short Name:
- J/ApJ/615/887
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present precise localizations of AXP 1E1841-045 and SGR 1627-41 with Chandra. We obtained new infrared observations of SGR 1627-41 and reanalyzed archival observations of AXP 1E1841-045 in order to refine their positions and search for infrared counterparts.
