- ID:
- ivo://CDS.VizieR/II/305
- Title:
- SAGE LMC and SMC IRAC Source Catalog
- Short Name:
- II/305
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The SAGE project is a Cycle 2 legacy program on the Spitzer Space Telescope, entitled, "Spitzer Survey of the Large Magellanic Cloud: Surveying the Agents of a Galaxy's Evolution (SAGE)", with Margaret Meixner (STScI) as the PI. The project overview and initial results are described in a paper by Meixner et al. (2006AJ....132.2268M). The Catalog is a highly reliable list of 6.4 million sources. Faint limits for SAGE are 18.1, 17.5, 15.3, and 14.2 for IRAC 3.6, 4.5, 5.8, 8.0 um, respectively. The SAGE-SMC project is a Cycle 4 legacy program on the Spitzer Space Telescope, entitled, "SAGE-SMC: Surveying the Agents of Galaxy Evolution in the Tidally-Disrupted, Low-Metallicity Small Magellanic Cloud", with Karl Gordon (STScI) as the PI. The project overview and initial results are described in a paper by Gordon et al. (2011AJ....142..102G). The Catalog is a highly reliable list of 2.0 million sources. Faint limits for SAGE-SMC are 18.3, 17.7, 15.7, and 14.5 for IRAC 3.6, 4.5, 5.8, 8.0 um, respectively. The archive tables are more complete but less reliable than the catalogs. IRAC Single Frame + Mosaic Photometry Catalog: a combination of mosaic photometry source list extracted from the combined Epoch 1 and Epoch 2 12 second frametime mosaics with all-epochs single frame source list, bandmerged with 2MASS or 2MASS6X. Detailed documentations are available from http://irsa.ipac.caltech.edu/data/SPITZER/SAGE/doc/ as SAGEDataProductsDescription_Sep09.pdf and from http://irsa.ipac.caltech.edu/data/SPITZER/SAGE-SMC/docs/ as sage-smc_delivery_apr11.pdf
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/470/3250
- Title:
- SAGE LMC point-sources classification
- Short Name:
- J/MNRAS/470/3250
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Infrared Spectrograph (IRS) on the Spitzer Space Telescope observed nearly 800 point sources in the Large Magellanic Cloud (LMC), taking over 1000 spectra. 197 of these targets were observed as part of the SAGE-Spec Spitzer Legacy program; the remainder are from a variety of different calibration, guaranteed time and open time projects. We classify these point sources into types according to their infrared spectral features, continuum and spectral energy distribution shape, bolometric luminosity, cluster membership and variability information, using a decision-tree classification method. We then refine the classification using supplementary information from the astrophysical literature. We find that our IRS sample is comprised substantially of YSO and HII regions, post-main-sequence low-mass stars: (post-)asymptotic giant branch stars and planetary nebulae and massive stars including several rare evolutionary types. Two supernova remnants, a nova and several background galaxies were also observed. We use these classifications to improve our understanding of the stellar populations in the LMC, study the composition and characteristics of dust species in a variety of LMC objects, and to verify the photometric classification methods used by mid-IR surveys. We discover that some widely used catalogues of objects contain considerable contamination and others are missing sources in our sample.
- ID:
- ivo://CDS.VizieR/J/MNRAS/457/2814
- Title:
- SAGE SMC evolved stars candidates
- Short Name:
- J/MNRAS/457/2814
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The life cycle of dust in the interstellar medium is heavily influenced by outflows from asymptotic giant branch (AGB) and red supergiant (RSG) stars, a large fraction of which is contributed by a few very dusty sources. We compute the dust input to the Small Magellanic Cloud (SMC) by fitting the multi-epoch mid-infrared spectral energy distributions of AGB/RSG candidates with models from the Grid of RSG and AGB ModelS grid, allowing us to estimate the luminosities and dust-production rates (DPRs) of the entire population. By removing contaminants, we guarantee a high-quality data set with reliable DPRs and a complete inventory of the dustiest sources. We find a global AGB/RSG dust-injection rate of (1.3+/-0.1)x10^-6^M_{sun}_/yr, in agreement with estimates derived from mid-infrared colours and excess fluxes. As in the Large Magellanic Cloud, a majority (66 per cent) of the dust arises from the extreme AGB stars, which comprise only ~7 per cent of our sample. A handful of far-infrared sources, whose 24{mu}m fluxes exceed their 8{mu}m fluxes, dominate the dust input. Their inclusion boosts the global DPR by ~1.5x, making it necessary to determine whether they are AGB stars. Model assumptions, rather than missing data, are the major sources of uncertainty; depending on the choice of dust shell expansion speed and dust optical constants, the global DPR can be up to ~10 times higher. Our results suggest a non-stellar origin for the SMC dust, barring as yet undiscovered evolved stars with very high DPRs.
- ID:
- ivo://CDS.VizieR/J/ApJ/778/15
- Title:
- SAGE-SMC III. Young stellar objects
- Short Name:
- J/ApJ/778/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Spitzer Space Telescope Legacy Program SAGE-SMC allows global studies of resolved stellar populations in the SMC in a different environment than our Galaxy. Using the SAGE-SMC IRAC (3.6-8.0{mu}m) and MIPS (24 and 70{mu}m) catalogs and images combined with near-infrared (JHK_s_) and optical (UBVI) data, we identified a population of ~1000 intermediate - to high-mass young stellar objects (YSOs) in the SMC (three times more than previously known). Our method of identifying YSO candidates builds on the method developed for the Large Magellanic Cloud by Whitney et al. (2008, J/AJ/136/18) with improvements based on what we learned from our subsequent studies and techniques described in the literature. We perform (1) color-magnitude cuts based on five color-magnitude diagrams (CMDs), (2) visual inspection of multi-wavelength images, and (3) spectral energy distribution (SED) fitting with YSO models. For each YSO candidate, we use its photometry to calculate a measure of our confidence that the source is not a non-YSO contaminant, but rather a true YSO, based on the source's location in the color-magnitude space with respect to non-YSOs. We use this CMD score and the SED fitting results to define two classes of sources: high-reliability YSO candidates and possible YSO candidates. We found that, due to polycyclic aromatic hydrocarbon emission, about half of our sources have [3.6]-[4.5] and [4.5]-[5.8] colors not predicted by previous YSO models. The YSO candidates are spatially correlated with gas tracers.
- ID:
- ivo://CDS.VizieR/J/PASP/122/683
- Title:
- SAGE-Spec Spitzer legacy program
- Short Name:
- J/PASP/122/683
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The SAGE-Spec Spitzer Legacy program is a spectroscopic follow-up to the SAGE-LMC photometric survey of the Large Magellanic Cloud carried out with the Spitzer Space Telescope. We present an overview of SAGE-Spec and some of its first results. The SAGE-Spec program aims to study the life cycle of gas and dust in the Large Magellanic Cloud and to provide information essential to the classification of the point sources observed in the earlier SAGE-LMC photometric survey. We acquired 224.6h of observations using the infrared spectrograph and the spectral energy distribution (SED) mode of the Multiband Imaging Photometer for Spitzer. The SAGE-Spec data, along with archival Spitzer spectroscopy of objects in the Large Magellanic Cloud, are reduced and delivered to the community. We discuss the observing strategy, the specific data-reduction pipelines applied, and the dissemination of data products to the scientific community. Initial science results include the first detection of an extragalactic 21um feature toward an evolved star and elucidation of the nature of disks around RV Tauri stars in the Large Magellanic Cloud. Toward some young stars, ice features are observed in absorption. We also serendipitously observed a background quasar, at a redshift of z~~0.14, which appears to be hostless.
- ID:
- ivo://CDS.VizieR/J/MNRAS/430/2358
- Title:
- SDSS photometry of LMC cluster SL 529
- Short Name:
- J/MNRAS/430/2358
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results on the age and metallicity estimates of the poorly studied Large Magellanic Cloud (LMC) cluster SL 529, from CCD SDSS gr photometry obtained at the Gemini South telescope with the GMOS attached. The cluster main-sequence turnoffs (MSTO) region possesses an extended structure, with an age spread (~0.5Gyr) bigger than the mean age width of known extended MSTO (EMSTO) LMC clusters. We report for the first time a mean cluster age of 2.25Gyr and a mean cluster metallicity of Z=0.004, which place it as the most metal-poor and oldest cluster in the EMSTO LMC cluster group. In addition, the cluster red clump appears to be formed by two concentrations of stars - although it is not clear whether this feature can be caused, in part, by binary interactions and mergers - whereas the cluster core radius of 4.2pc is in excellent agreement with those determined for the previously 12 known EMSTO LMC clusters.
- ID:
- ivo://CDS.VizieR/J/A+AS/112/367
- Title:
- Selected Regions C and E in the LMC
- Short Name:
- J/A+AS/112/367
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD data of objects in the LMC selected regions C and E. These data include the young globular cluster NGC 1818, the association NGC 1948 and the intermediate age cluster NGC 1978. We discuss the calibration of the data and provide complete tables of the photometry and astrometry of all stars within our field of view.
- ID:
- ivo://CDS.VizieR/J/A+A/656/A66
- Title:
- Semi-regular red giants as distance indicators
- Short Name:
- J/A+A/656/A66
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Semi-regular variables (SRVs) are similar to Miras in brightness, and they also follow PLRs, though not necessarily the same as Miras. As potential standard candles they are more challenging than Miras due to their smaller variability amplitudes and less regular light curves, but they are substantially more numerous and especially promising to probe old stellar populations. We aim to characterize the variability of SRVs, with focus on their connection with Miras, in order to prepare the ground for investigating their potential as distance indicators. We examine SRVs and Miras in the Magellanic Clouds from OGLE-III observations, with data from Gaia and 2MASS. After cleaning the sample from variability periods unrelated to pulsation, we classify each source by chemical type and combination of pulsation modes. We examine the results in terms of global photometric and pulsation properties. We identify four SRVs groups that fit the general evolutionary scenario predicted by theory. SRVs dominated by fundamental-mode pulsation are very similar to Miras, especially if mono-periodic. They further split into two sub-groups, one of which follows the same sequence as Miras in the period-luminosity and period-amplitude diagram, without discontinuity. The similarities between Miras and SRVs suggest that the latter can be adopted as complementary distance indicators to the former, thereby at least doubling the available number of LPVs suitable for use as distance indicators. The traditional amplitude-based separation between Miras and SRVs is not necessarily appropriate, and a more physically sound criterion should also involve pulsation periods. While this would require comparatively longer time series, they are expected to become accessible in the coming years even for weak sources thanks to current and future large-scale surveys. The table of reclassified LPVs is made public.
- ID:
- ivo://CDS.VizieR/J/A+A/471/103
- Title:
- SIMBA observations of SMC
- Short Name:
- J/A+A/471/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CO observations have been the best way so far to trace molecular gas in external galaxies, but in low metallicity environments the gas mass deduced could be largely underestimated due to enhanced photodissociation of the CO molecule. Large envelopes of H_2_ could therefore be missed by CO observations. At present, the kinematic information of CO data cubes are used to estimate virial masses and trace the total mass of the molecular clouds. Millimeter dust emission can also be used as a dense gas tracer and could unveil H_2_ envelopes lacking CO. These different tracers must be compared in different environments. This study compares virial masses to masses deduced from millimeter emission, in two GMC samples: the local molecular clouds in our Galaxy (10^4^-10^5^M_{sun}_), and their equivalents in the Small Magellanic Cloud (SMC), one of the nearest low metallicity dwarf galaxies. In our Galaxy, mass estimates deduced from millimeter (FIRAS) emission are consistent with masses deduced from gamma ray analysis and therefore trace the total mass of the clouds. Virial masses are systematically larger (twice on average) than mass estimates from millimeter dust emission. This difference decreases toward high masses and has been reported in previous studies. This is not the case for SMC giant molecular clouds: molecular cloud masses deduced from SIMBA millimeter observations are systematically higher (twice on average for conservative values of the dust to gas ratio and dust emissivity) than the virial masses from SEST CO observations. The observed excess cannot be accounted for by any plausible change of dust properties. Taking a general form for the virial theorem, we show that a magnetic field strength of ~15{mu}G in SMC clouds could provide additional support for the clouds and explain the difference observed. We conclude that masses of SMC molecular clouds have so far been underestimated. Magnetic pressure may contribute significantly to their support.
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/1425
- Title:
- Single-mode OGLE Cepheids additional modes
- Short Name:
- J/MNRAS/478/1425
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Detailed knowledge of the variability of classical Cepheids, in particular their modulations and mode composition, provides crucial insight into stellar structure and pulsation. However, tiny modulations of the dominant radial-mode pulsation were recently found to be very frequent, possibly ubiquitous in Cepheids, which makes secondary modes difficult to detect and analyse, since these modulations can easily mask the potentially weak secondary modes. The aim of this study is to re-investigate the secondary mode content in the sample of OGLE-III and OGLE-IV single-mode classical Cepheids using kernel regression with adaptive kernel width for pre-whitening, instead of using a constant-parameter model. This leads to a more precise removal of the modulated dominant pulsation, and enables a more complete survey of secondary modes with frequencies outside a narrow range around the primary. Our analysis reveals that significant secondary modes occur more frequently among first overtone Cepheids than previously thought. The mode composition appears significantly different in the Large and Small Magellanic Clouds, suggesting a possible dependence on chemical composition. In addition to the formerly identified non-radial mode at P_2_~=0.6...0.65P_1_ (0.62-mode), and a cluster of modes with near-primary frequency, we find two more candidate non-radial modes. One is a numerous group of secondary modes with P_2_~=1.25P_1_, which may represent the fundamental of the 0.62-mode, supposed to be the first harmonic of an l {in} {7, 8, 9} non-radial mode. The other new mode is at P_2_ ~=1.46P_1_, possibly analogous to a similar, rare mode recently discovered among first overtone RR Lyrae stars.
