- ID:
- ivo://CDS.VizieR/J/ApJS/229/28
- Title:
- SFiNCs: X-ray, IR and membership catalogs
- Short Name:
- J/ApJS/229/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Star Formation in Nearby Clouds (SFiNCs) project is aimed at providing a detailed study of the young stellar populations and of star cluster formation in the nearby 22 star-forming regions (SFRs) for comparison with our earlier MYStIX survey of richer, more distant clusters. As a foundation for the SFiNCs science studies, here, homogeneous data analyses of the Chandra X-ray and Spitzer mid-infrared archival SFiNCs data are described, and the resulting catalogs of over 15300 X-ray and over 1630000 mid-infrared point sources are presented. On the basis of their X-ray/infrared properties and spatial distributions, nearly 8500 point sources have been identified as probable young stellar members of the SFiNCs regions. Compared to the existing X-ray/mid-infrared publications, the SFiNCs member list increases the census of YSO members by 6%-200% for individual SFRs and by 40% for the merged sample of all 22 SFiNCs SFRs.
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- ID:
- ivo://CDS.VizieR/J/A+A/604/A6
- Title:
- SgrB2 ALMA continuum and spectral index
- Short Name:
- J/A+A/604/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The two hot molecular cores SgrB2(M) and SgrB2(N), which are located at the center of the giant molecular cloud complex Sagittarius B2, have been the targets of numerous spectral line surveys, revealing a rich and complex chemistry. We seek to characterize the physical and chemical structure of the two high-mass star-forming sites SgrB2(M) and SgrB2(N) using high-angular resolution observations at millimeter wavelengths, reaching spatial scales of about 4000au. We used the Atacama Large Millimeter/submillimeter Array (ALMA) to perform an unbiased spectral line survey of both regions in the ALMA band 6 with a frequency coverage from 211GHz to 275GHz. The achieved angular resolution is 0.4-arcsec, which probes spatial scales of about 4000au, i.e., able to resolve different cores and fragments. In order to determine the continuum emission in these line-rich sources, we used a new statistical method, STATCONT, which has been applied successfully to this and other ALMA datasets and to synthetic observations. We detect 27 continuum sources in SgrB2(M) and 20 sources in SgrB2(N). We study the continuum emission variation across the ALMA band 6 (i.e., spectral index) and compare the ALMA 1.3mm continuum emission with previous SMA 345GHz and VLA 40GHz observations to study the nature of the sources detected. The brightest sources are dominated by (partially optically thick) dust emission, while there is an important degree of contamination from ionized gas free-free emission in weaker sources. While the total mass in SgrB2(M) is distributed in many fragments, most of the mass in SgrB2(N) arises from a single object, with filamentary-like structures converging toward the center. There seems to be a lack of low-mass dense cores in both regions. We determine H2 volume densities for the cores of about 10^7^-10^9^cm^-3^ (or 10^5^-10^7^M_{sun}_/pc^3^), i.e., one to two orders of magnitude higher than the stellar densities of super star clusters. We perform a statistical study of the chemical content of the identified sources. In general, SgrB2(N) is chemically richer than SgrB2(M). The chemically richest sources have about 100 lines per GHz and the fraction of luminosity contained in spectral lines at millimeter wavelengths with respect to the total luminosity is about 20%-40%. There seems to be a correlation between the chemical richness and the mass of the fragments, where more massive clumps are more chemically rich. Both SgrB2(N) and SgrB2(M) harbor a cluster of hot molecular cores. We compare the continuum images with predictions from a detailed 3D radiative transfer model that reproduces the structure of SgrB2 from 45pc down to 100au. This ALMA dataset, together with other ongoing observational projects in the range 5GHz to 200GHz, better constrain the 3D structure of SgrB2 and allow us to understand its physical and chemical structure.
- ID:
- ivo://CDS.VizieR/J/A+A/552/L2
- Title:
- SINFONI K-band observations of IRS54(YLW52)
- Short Name:
- J/A+A/552/L2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Molecular outflows from very low-mass stars (VLMSs) and brown dwarfs have been studied very little. So far, only a few CO outflows have been observed, allowing us to map the immediate circumstellar environment. We present the first spatially resolved H_2_ emission around IRS54 (YLW52), a ~0.1-0.2M_{sun}_ Class I source. By means of VLT SINFONI K-band observations, we probed the H2 emission down to the first ~50AU from the source. The molecular emission shows a complex structure delineating a large outflow cavity and an asymmetric molecular jet. Thanks to the detection of several H_2_transitions, we are able to estimate average values along the jet-like structure (from source position to knot D) of Av~28mag, T~2000-3000K, and H_2_column density N(H_2)~1.7x10^17cm^-2. This allows us to estimate a mass loss rate of ~2x10^-10M_{sun}_/yr for the warm H_2_component . In addition, from the total flux of the Br gamma line, we infer an accretion luminosity and mass accretion rate of 0.64L_{sun}_ and ~3x10^-7M_{sun}_/yr, respectively. The outflow structure is similar to those found in low-mass Class I and CTTS. However, the Lacc/Lbol ratio is very high (~80%), and the mass accretion rate is about one order of magnitude higher when compared to objects of roughly the same mass, pointing to the young nature of the investigated source.
- ID:
- ivo://CDS.VizieR/J/ApJ/655/212
- Title:
- S3MC IRAC and MIPS photometry
- Short Name:
- J/ApJ/655/212
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the initial results from the Spitzer Survey of the Small Magellanic Cloud (S^3^MC), which imaged the star-forming body of the SMC in all seven MIPS and IRAC wave bands. We find that the F8/F24 ratio (an estimate of PAH abundance) has large spatial variations and takes a wide range of values that are unrelated to metallicity but anticorrelated with 24um brightness and F24/F70 ratio. This suggests that photodestruction is primarily responsible for the low abundance of PAHs observed in star-forming low-metallicity galaxies. We use the S^3^MC images to compile a photometric catalog of 400000 mid- and far-infrared point sources in the SMC.
- ID:
- ivo://CDS.VizieR/J/ApJ/669/327
- Title:
- S3MC: YSOs in N66, in SMC
- Short Name:
- J/ApJ/669/327
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use Spitzer Space Telescope observations from the Spitzer Survey of the Small Magellanic Cloud (S^3^MC) to study the young stellar content of N66, the largest and brightest HII region in the SMC. In addition to large numbers of normal stars, we detect a significant population of bright, red infrared sources that we identify as likely to be young stellar objects (YSOs). We use spectral energy distribution (SED) fits to classify objects as ordinary (main-sequence or red giant) stars, asymptotic giant branch stars, background galaxies, and YSOs.
- ID:
- ivo://CDS.VizieR/J/ApJ/843/33
- Title:
- SOFIA Massive (SOMA) Star Formation Survey. I.
- Short Name:
- J/ApJ/843/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an overview and first results of the Stratospheric Observatory For Infrared Astronomy Massive (SOMA) Star Formation Survey, which is using the FORCAST instrument to image massive protostars from ~10 to 40{mu}m. These wavelengths trace thermal emission from warm dust, which in Core Accretion models mainly emerges from the inner regions of protostellar outflow cavities. Dust in dense core envelopes also imprints characteristic extinction patterns at these wavelengths, causing intensity peaks to shift along the outflow axis and profiles to become more symmetric at longer wavelengths. We present observational results for the first eight protostars in the survey, i.e., multiwavelength images, including some ancillary ground-based mid- infrared (MIR) observations and archival Spitzer and Herschel data. These images generally show extended MIR/FIR emission along directions consistent with those of known outflows and with shorter wavelength peak flux positions displaced from the protostar along the blueshifted, near-facing sides, thus confirming qualitative predictions of Core Accretion models. We then compile spectral energy distributions and use these to derive protostellar properties by fitting theoretical radiative transfer models. Zhang and Tan models, based on the Turbulent Core Model of McKee and Tan, imply the sources have protostellar masses m*~10-50M_{sun}_ accreting at ~10^-4^-10^-3^M_{sun}_/yr inside cores of initial masses Mc~30-500M_{sun}_ embedded in clumps with mass surface densities {Sigma}_cl_~0.1-3g/cm^2^. Fitting the Robitaille et al. models typically leads to slightly higher protostellar masses, but with disk accretion rates ~100x smaller. We discuss reasons for these differences and overall implications of these first survey results for massive star formation theories.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A172
- Title:
- Solar neighbourhood young stars 3D mapping
- Short Name:
- J/A+A/620/A172
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the three dimensional arrangement of young stars in the solar neighbourhood using the second release of the Gaia mission (Gaia DR2) and we provide a new, original view of the spatial configuration of the star forming regions within 500pc from the Sun. By smoothing the star distribution through a gaussian filter, we construct three dimensional density maps for early-type stars (upper-main sequence, UMS) and pre-main sequence (PMS) sources. The PMS and the UMS samples are selected through a combination of photometric and astrometric criteria. A side product of the analysis is a three dimensional, G-band extinction map, which we use to correct our colour-magnitude diagram for extinction and reddening. Both density maps show three prominent structures, Scorpius-Centaurus, Orion, and Vela. The PMS map shows a plethora of lower mass star forming regions, such as Taurus, Perseus, Cepheus, Cassiopeia and Lacerta, which are less visible in the UMS map, due to the lack of large numbers of bright, early-type stars. We report the finding of a candidate new open cluster towards l, b ~218.5{deg}, -2{deg}, which could be related to the Orion star forming complex. We estimate ages for the PMS sample and we study the distribution of PMS stars as a function of their age. We find that younger stars cluster in dense, compact clumps, and are surrounded by older sources, whose distribution is instead more diffuse. The youngest groups that we find are mainly located in Scorpius-Centaurus, Orion, Vela and Taurus. Cepheus, Cassiopeia, and Lacerta are instead more evolved and less numerous. Finally, we find that the three dimensional density maps show no evidence for the existence of the ring-like structure which is usually referred to as the Gould Belt.
- ID:
- ivo://CDS.VizieR/J/A+A/640/A75
- Title:
- SOLIS. X. NGC 1333 IRAS 4A images
- Short Name:
- J/A+A/640/A75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The interstellar complex organic molecules (iCOMs) are C-bearing molecules containing at least six atoms; two main proposals for their formation are suggested: a direct formation in the icy mantle of the dust grains and formation through the reaction in gas phase of released grain mantle species. The shocked gas along outflows driven by low-mass protostars is a unique environment to study how the iCOMs can be formed as the composition of the dust mantles is sputtered into the gas phase. The chemical richness in shocked material associated with low-mass protostellar outflows has been so far studied in the prototypical L1157 blue-shifted outflow to investigate the iCOM formation routes. To understand whether the case of L1157-B1 is unique, we imaged and studied the IRAS 4A outflows in the NGC 1333 star forming region. We used the NOrthern Extended Millimeter Array (NOEMA) interferometer as part of the IRAM Seeds Of Life in Space (SOLIS) Large Program to image the large-scale bipolar outflows driven by the IRAS 4A system in the 3 mm band, and we compared the observation with the GRAINOBLE+ astrochemical model. We report the first detection, in the IRAS 4A outflows, of several iCOMs: six lines of methanol (CH_3_OH), eight of acetaldehyde (CH_3_CHO), one of formamide (NH_2_CHO), and four of dimethyl ether (CH_3_OCH_3_), all sampling upper excitation energy up to 30K. We found a significant chemical differentiation between the southeast outflow driven by the IRAS 4A1 protostar, showing a richer molecular content, and the north-southwest one driven by the IRAS 4A2 hot corino. The CH_3_OH/CH_3_CHO abundance ratio is lower by a factor of 4 in the former; furthermore, the ratio in the IRAS 4A outflows is lower by a factor of 10 with respect to the values found in different hot corinos. After L1157-B1, the IRAS 4A outflow is now the second outflow to show an evident chemical complexity. Given that CH_3_OH is a grain surface species, the astrochemical gas-phase model run with GRAINOBLE+ reproduced our observation assuming that acetaldehyde is formed mainly through the gas-phase reaction of the ethyl radical (CH_3_CH_2_) and atomic oxygen. Furthermore, the chemical differentiation between the two outflows suggests that the IRAS 4A1 outflow is likely younger than that of the IRAS 4A2. Further investigation is needed to constrain the age of the outflow. In addition, observation of even younger shocks are necessary. In order to provide strong constraints on the CH_3_CHO formation mechanisms it would be interesting to observe CH_3_CH_2_, but given that its frequencies are not known, future spectroscopic studies on this species are needed.
- ID:
- ivo://CDS.VizieR/J/ApJ/785/159
- Title:
- SONYC census of substellar objects in Lupus 3
- Short Name:
- J/ApJ/785/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- SONYC -Substellar Objects in Nearby Young Clusters- is a survey program to investigate the frequency and properties of substellar objects in nearby star-forming regions. We present a new imaging and spectroscopic survey conducted in the young (~1 Myr), nearby (~200 pc) star-forming region Lupus 3. Deep optical and near-infrared images were obtained with MOSAIC-II and NEWFIRM at the CTIO 4 m telescope, covering ~1.4 deg^2^ on the sky. The i-band completeness limit of 20.3 mag is equivalent to 0.009-0.02 M_{sun}_, for A_V_<=5. Photometry and 11-12 yr baseline proper motions were used to select candidate low-mass members of Lupus 3. We performed a spectroscopic follow-up of 123 candidates, using VIMOS at the Very Large Telescope, and we identify 7 probable members, among which 4 have spectral type later than M6.0 and T_eff_<=3000 K, i.e., are probably substellar in nature. Two of the new probable members of Lupus 3 appear underluminous for their spectral class and exhibit emission line spectrum with strong H_{alpha}_ or forbidden lines associated with active accretion. We derive a relation between the spectral type and effective temperature: T_eff_=(4120+/-175)-(172+/-26)xSpT, where SpT refers to the M spectral subtype between 1 and 9. Combining our results with the previous works on Lupus 3, we show that the spectral type distribution is consistent with that in other star-forming regions, as well as the derived star-to-brown dwarf ratio of 2.0-3.3. We compile a census of all spectroscopically confirmed low-mass members with spectral type M0 or later.
- ID:
- ivo://CDS.VizieR/J/ApJ/744/6
- Title:
- SONYC census of very low-mass objects in NGC1333
- Short Name:
- J/ApJ/744/6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- SONYC - Substellar Objects in Nearby Young Clusters - is a program to investigate the frequency and properties of young substellar objects with masses down to a few times that of Jupiter. In a series of papers we have obtained follow-up spectroscopy for a large number of candidate very low mass (VLM) members of the ~1Myr old cluster NGC1333 in the Perseus star forming region. For more details on the survey, see the associated paper (Scholz et al., 2012ApJ...744....6S). Here we present a census of spectroscopically confirmed very low mass objects in NGC1333. We include all objects with spectral type of M5 or later and/or effective temperature of 3200K or cooler. In total, there are now 58 objects which fulfill these criteria. In three tables we list photometric and spectroscopic properties for our own sample as well as for objects listed in the literature. In addition, we also include three tables of the objects that have been rejected as very low mass cluster members based on our spectroscopic follow-up. Finally, we attach the two photometric candidate lists from which the spectroscopic sample was extracted, see Scholz et al. (2012ApJ...756...24S) for more details on these catalogues.
