- ID:
- ivo://CDS.VizieR/J/ApJ/813/29
- Title:
- Classical and type II Cepheids IR excesses
- Short Name:
- J/ApJ/813/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectral energy distributions for 132 classical and type II Cepheids were searched for evidence of excess flux above the photospheric level in the mid-infrared. Eight of them were found to have unambiguously strong excess emission while a further 13 showed evidence of weak emission. The presence of emission appears to be unrelated to either the pulsational amplitude or the effective temperature while strong emission is limited to stars with periods longer than 11 days, with a single exception. For the stars with strong emission we attempted to fit the energy distribution with a stellar wind model. No acceptable fit could be found for silicate grains. With graphite or iron grains we could only obtain an acceptable fit if the maximum dust temperature was significantly lower than the condensation temperature. We conclude that the excess emission is not evidence of mass loss.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/152/201
- Title:
- Classification of 2000 bright IRAS sources
- Short Name:
- J/ApJS/152/201
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An artificial neural network (ANN) scheme has been employed that uses a supervised back-propagation algorithm to classify 2000 bright sources from the Calgary database of Infrared Astronomical Satellite (IRAS) spectra in the region 8-23{mu}m. The database has been classified into 17 predefined classes based on the spectral morphology. We have been able to classify over 80% of the sources correctly in the first instance. The speed and robustness of the scheme will allow us to classify the whole of the Low Resolution Spectrometer database, containing more than 50,000 sources, in the near future.
- ID:
- ivo://CDS.VizieR/J/A+A/453/535
- Title:
- Classification of bright mid-IR sources
- Short Name:
- J/A+A/453/535
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Context: The stellar populations in the central region of the Galaxy are poorly known because of the high visual extinction and very great source density in this direction. Aims: To use recent infrared surveys for studying the dusty stellar objects in this region. Methods: We analyse the content of a ~20x20arcmin^2 field centred at (l,b)=(-0.27,-0.06) observed at 7 and 15 microns as part of the ISOGAL survey. These ISO observations are more than an order of magnitude better in sensitivity and spatial resolution than the IRAS observations. The sources are cross-associated with other catalogues to identify various types of objects. We then derive criteria to distinguish young objects from post-main sequence stars. Results: We find that a sample of about 50 young stellar objects and ultra-compact HII regions emerges, out of a population of evolved AGB stars. We demonstrate that the sources colours and spatial extents, as they appear in the ISOGAL catalogue, possibly complemented with MSX photometry at 21 microns, can be used to determine whether the ISOGAL sources brighter than 300mJy at 15 microns (or [15]<4.5mag) are young objects or late-type evolved stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/112/557
- Title:
- Classification of IRAS Sources
- Short Name:
- J/ApJS/112/557
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IRAS low-resolution spectra were extracted for 11,224 IRAS sources. These spectra were classified into astrophysical classes, based on the presence of emission and absorption features and on the shape of the continuum. Counterparts of these IRAS sources in existing optical and infrared catalogs are identified, and their optical spectral types are listed if they are known. The correlations between the photospheric/ optical and circumstellar/infrared classifications are discussed.
- ID:
- ivo://CDS.VizieR/J/ApJ/646/161
- Title:
- Classification of IR galaxies
- Short Name:
- J/ApJ/646/161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Mid-infrared diagnostics are presented for a large portion of the Spitzer Infrared Nearby Galaxies Survey (SINGS) sample plus archival data from ISO and Spitzer. The SINGS data set includes low- and high-resolution spectral maps and broadband imaging in the infrared for over 160 nuclear and extranuclear regions within 75 nearby galaxies spanning a wide range of morphologies, metallicities, luminosities, and star formation rates. Our main result is that these mid-infrared diagnostics effectively constrain a targets dominant power source. The combination of a high-ionization line index and PAH strength serves as an efficient discriminant between AGNs and star-forming nuclei, confirming progress made with ISO spectroscopy on starbursting and ultraluminous infrared galaxies. The sensitivity of Spitzer allows us to probe fainter nuclear and star-forming regions within galaxy disks.
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/3504
- Title:
- Classification of IRS sources in the SMC
- Short Name:
- J/MNRAS/451/3504
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Magellanic clouds are uniquely placed to study the stellar contribution to dust emission. Individual stars can be resolved in these systems even in the mid-infrared, and they are close enough to allow detection of infrared excess caused by dust. We have searched the Spitzer Space Telescope data archive for all Infrared Spectrograph (IRS) staring-mode observations of the Small Magellanic Cloud (SMC) and found that 209 Infrared Array Camera (IRAC) point sources within the footprint of the Surveying the Agents of Galaxy Evolution in the Small Magellanic Cloud (SAGE-SMC) Spitzer Legacy programme were targeted, within a total of 311 staring mode observations. We classify these point sources using a decision tree method of object classification, based on infrared spectral features, continuum and spectral energy distribution shape, bolometric luminosity, cluster membership and variability information. We find 58 asymptotic giant branch (AGB) stars, 51 young stellar objects (YSOs), 4 post-AGB objects, 22 Red Supergiants (RSGs), 27 stars (of which 23 are dusty OB stars), 24 planetary nebulae (PNe), 10 Wolf-Rayet (WR) stars, 3 HII regions, 3 R Coronae Borealis (R CrB) stars, 1 Blue Supergiant and 6 other objects, including 2 foreground AGB stars. We use these classifications to evaluate the success of photometric classification methods reported in the literature.
- ID:
- ivo://CDS.VizieR/J/A+A/590/A33
- Title:
- Class 0 sources continuum subtracted UV-tables
- Short Name:
- J/A+A/590/A33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The physical structure of deeply-embedded low-mass protostars (Class 0) on scales of less than 300AU is still poorly constrained. While molecular line observations demonstrate the presence of disks with Keplerian rotation toward a handful of sources, others show no hints of rotation. Determining the structure on small scales (few 100AU) is crucial for understanding the physical and chemical evolution from cores to disks. To determine the presence and characteristics of compact, disk-like structures in deeply-embedded low-mass protostars. A related goal is to investigate how the derived structure affects the determination of gas-phase molecular abundances on hot-core scales. Two models of the emission, a Gaussian disk intensity distribution and a parametrized power-law disk model, are fitted to sub-arcsecond resolution interferometric continuum observations of five Class 0 sources, including one source with a confirmed Keplerian disk. Prior to fitting the models to the de-projected real visibilities, the estimated envelope from an independent model and any companion source are subtracted. For reference, a spherically symmetric single power-law envelope is fitted to the larger scale (~1000AU) emission and investigated further for one of the sources on smaller scales.
- ID:
- ivo://CDS.VizieR/J/ApJ/841/109
- Title:
- Cloud decomposition & SFR measurements
- Short Name:
- J/ApJ/841/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galactic star formation scaling relations show increased scatter from kpc to sub-kpc scales. Investigating this scatter may hold important clues to how the star formation process evolves in time and space. Here, we combine different molecular gas tracers, different star formation indicators probing distinct populations of massive stars, and knowledge of the evolutionary state of each star-forming region to derive the star formation properties of ~150 star-forming complexes over the face of the Large Magellanic Cloud (LMC). We find that the rate of massive star formation ramps up when stellar clusters emerge and boost the formation of subsequent generations of massive stars. In addition, we reveal that the star formation efficiency of individual giant molecular clouds (GMCs) declines with increasing cloud gas mass (M_cloud_). This trend persists in Galactic star-forming regions and implies higher molecular gas depletion times for larger GMCs. We compare the star formation efficiency per freefall time ({epsilon}_ff_) with predictions from various widely used analytical star formation models. While these models can produce large dispersions in {epsilon}_ff_ similar to those in observations, the origin of the model-predicted scatter is inconsistent with observations. Moreover, all models fail to reproduce the observed decline of {epsilon}_ff_ with increasing M_cloud_ in the LMC and the Milky Way. We conclude that analytical star formation models idealizing global turbulence levels and cloud densities and assuming a stationary star formation rate (SFR) are inconsistent with observations from modern data sets tracing massive star formation on individual cloud scales. Instead, we reiterate the importance of local stellar feedback in shaping the properties of GMCs and setting their massive SFR.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A156
- Title:
- Cluster formation toward Be87/ON2. I.
- Short Name:
- J/A+A/650/A156
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Disentangling line-of-sight alignments of young stellar populations is crucial for observational studies of star-forming complexes. This task is particularly problematic in a Cygnus-X subregion where several components, located at different distances, overlap: the Berkeley 87 young massive cluster, the poorly known [DB2001] Cl05 embedded cluster, and the ON2 star-forming complex, which in turn is composed of several HII regions. We provide a methodology for building an exhaustive census of young objects that can consistently treat large differences in extinction and distance. OMEGA2000 near-infrared observations of the Berkeley 87 / ON2 field were merged with archival data from Gaia, Chandra, Spitzer, and Herschel, and with cross-identifications from the literature. To address the incompleteness effects and selection biases that arise from the line-of-sight overlap, we adapted existing methods for extinction estimation and young object classification. We also defined the intrinsic reddening index, R_int_, a new tool for separating intrinsically red sources from those whose infrared color excess is caused by extinction. Finally, we introduce a new method for finding young stellar objects based on R_int_. We find 571 objects whose classification is related to recent or ongoing star formation. Together with other point sources with individual estimates of distance or extinction, we compile a catalog of 3005 objects to be used for further membership work. A new distance for Berkeley 87, (1673+/-17)pc, is estimated as a median of 13 spectroscopic members with accurate Gaia EDR3 parallaxes. The flexibility of our approach, especially regarding the R_int_ definition, allows overcoming photometric biases caused by large variations in extinction and distance, in order to obtain homogeneous catalogs of young sources. The multiwavelength census that results from applying our methods to the Berkeley 87 / ON2 field will serve as a basis for disentangling the overlapped populations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/427/1830
- Title:
- 20cm survey of the AKARI SEP (ATCA-ADFS)
- Short Name:
- J/MNRAS/427/1830
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a deep radio survey at 20cm wavelength are reported for a region containing the AKARI Deep Field South (ADF-S) near the South Ecliptic Pole (SEP), using the Australia Telescope Compact Array (ATCA). The survey (hereafter referred to as the ATCA-ADFS survey) has 1{sigma} detection limits ranging from 18.7 to 50{mu}Jy/beam over an area of ~1.1deg^2^, and ~ 2.5deg^2^ to lower sensitivity. The observations, data reduction and source count analysis are presented along with a description of the overall scientific objectives, and a catalogue containing 530 radio sources detected with a resolution of 6.2x4.9arcsec.
