- ID:
- ivo://CDS.VizieR/J/A+A/627/A135
- Title:
- VRI photometry of IC5070 variable stars
- Short Name:
- J/A+A/627/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed a field of 16'x16' in the star-forming region Pelican Nebula (IC 5070) at BVRI wavelengths for 90 nights spread over one year in 2012-2013. More than 250 epochs in VRI-bands are used to identify and classify variables up to V~21mag. We present a catalogue of optical time-series photometry with periods, mean-magnitudes and classifications for 95 variable stars including 67 pre-main-sequence variables towards star-forming region IC 5070. The pre-main-sequence variables are further classified as candidate classical T Tauri and weak-line T Tauri stars based on their light curve variations and the locations on the color-color and color-magnitude diagrams using optical and infrared data together with Gaia DR2 astrometry. Classical T Tauri stars display variability amplitudes up to three times the maximum fluctuation in disk-free weak-line T Tauri stars, which show strong periodic variations. Short-term variability is missed in our photometry within single nights. Several classical T Tauri stars display long-lasting (>10 days) single or multiple fading and brightening events up to a couple of magnitudes at optical wavelengths.
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- ID:
- ivo://CDS.VizieR/J/AJ/154/163
- Title:
- WISE-selected candidate SFRs beyond the Outer Arm
- Short Name:
- J/AJ/154/163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The outer Galaxy beyond the Outer Arm provides a good opportunity to study star formation in an environment significantly different from that in the solar neighborhood. However, star-forming regions in the outer Galaxy have never been comprehensively studied or cataloged because of the difficulties in detecting them at such large distances. We studied 33 known young star-forming regions associated with 13 molecular clouds at R_G_>=13.5 kpc in the outer Galaxy with data from the Wide-field Infrared Survey Explorer (WISE) mid-infrared all-sky survey (Wright et al. 2010AJ....140.1868W; Jarrett et al. 2011ApJ...735..112J). From their color distribution, we developed a simple identification criterion of star-forming regions in the outer Galaxy with the WISE color. We applied the criterion to all the WISE sources in the molecular clouds in the outer Galaxy at R_G_>=13.5 kpc detected with the Five College Radio Astronomy Observatory (FCRAO) ^12^CO survey of the outer Galaxy (Heyer et al. 1998ApJS..115..241H), of which the survey region is 102.49{deg}=<l=<141.54{deg}, -3.03{deg}=<b=<5.41{deg}, and successfully identified 711 new candidate star-forming regions in 240 molecular clouds. The large number of samples enables us to perform the statistical study of star formation properties in the outer Galaxy for the first time. This study is crucial to investigate the fundamental star formation properties, including star formation rate, star formation efficiency, and initial mass function, in a primordial environment such as the early phase of the Galaxy formation.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A30
- Title:
- W51 North ALMA 1.3 and 3mm images
- Short Name:
- J/A+A/657/A30
- Date:
- 21 Mar 2022 09:31:18
- Publisher:
- CDS
- Description:
- The fragmentation process in massive star-forming regions is one of the contemporary problems in astrophysics, and several physical processes have been proposed to control the fragmentation including turbulence, magnetic field, rotation, stellar feedback, and gravity. However, the fragmentation process has been poorly studied at small spatial scales well below 1000AU. W51 IRS2 is a well known massive star-forming region whose fragmentation properties have not been well investigated yet. We aim to use ALMA (Atacama Large Millimeter and Submillimeter Array) high angular resolution data to identify the fragments in W51 IRS2 and to study the fragmentation properties on a spatial scale of 0.04" (200AU). We used ALMA data of W51 IRS2 from three projects, which give an angular resolution of 0.028" (144AU) at millimeter wavelengths. The continuum images reveal significant substructure in an east-west ridge, where both W51 North and W51d2 are embedded. A spectral index map has been generated from the 3 and 1.3mm high-resolution continuum images.We identified compact fragments by using uv-range constrained 1.3mm continuum data. A Mean Surface Density of Companions (MSDC) analysis has been performed to study the separations between fragments. A total number of 33 continuum sources are identified and 29 out of them are defined as fragments in the surveyed region.The MSDC analysis reveals two breaks corresponding to spatial sales of 1845AU and 7346AU, indicative of a two-level clustering phenomenon, along with a linear regime below 1845AU, mostly associated with W51 North, whose slope is consistent with the slope for the clustering regime of other cluster-like regions in the Galaxy. The typical masses and separations of the fragments as well as the relation between density and number of fragments can be explained through a thermal Jeans process operating at high temperatures of 200-400K, consistent with previous measurements of the temperature in the region, and produced by the nearby massive stars. Therefore, although W51 IRS2 seems to be undergoing a thermally inhibited fragmentation phase, this does not seem to prevent the formation of a protocluster associated with W51 North.
- ID:
- ivo://CDS.VizieR/J/AJ/155/109
- Title:
- Young binaries in Ophiuchus&Upper Centaurus-Lupus
- Short Name:
- J/AJ/155/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of the orbital positions and flux ratios of 17 binary and triple systems in the Ophiuchus star-forming region and the Upper Centaurus-Lupus cluster based on adaptive optics imaging at the Keck Observatory. We report the detection of visual companions in MML 50 and MML 53 for the first time, as well as the possible detection of a third component in WSB 21. For six systems in our sample, our measurements provide a second orbital position following their initial discoveries over a decade ago. For eight systems with sufficient orbital coverage, we analyze the range of orbital solutions that fit the data. Ultimately, these observations will help provide the groundwork toward measuring precise masses for these pre-main-sequence stars and understanding the distribution of orbital parameters in young multiple systems.
- ID:
- ivo://CDS.VizieR/J/AJ/159/200
- Title:
- Young stellar objects in Lupus star-forming region
- Short Name:
- J/AJ/159/200
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The identification and characterization of stellar members within a star-forming region are critical to many aspects of star formation, including formalization of the initial mass function, circumstellar disk evolution, and star formation history. Previous surveys of the Lupus star-forming region have identified members through infrared excess and accretion signatures. We use machine learning to identify new candidate members of Lupus based on surveys from two space-based observatories: ESA's Gaia and NASA's Spitzer. Astrometric measurements from Gaia's Data Release 2 and astrometric and photometric data from the Infrared Array Camera on the Spitzer Space Telescope, as well as from other surveys, are compiled into a catalog for the random forest (RF) classifier. The RF classifiers are tested to find the best features, membership list, non-membership identification scheme, imputation method, training set class weighting, and method of dealing with class imbalance within the data. We list 27 candidate members of the Lupus star-forming region for spectroscopic follow-up. Most of the candidates lie in Clouds V and VI, where only one confirmed member of Lupus was previously known. These clouds likely represent a slightly older population of star formation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/477/3369
- Title:
- Young stellar objects in W49A and W51
- Short Name:
- J/MNRAS/477/3369
- Date:
- 17 Jan 2022 00:25:04
- Publisher:
- CDS
- Description:
- We have compared the star-formation properties of the W49A and W51 regions by using far-infrared data from the Herschel infrared Galactic Plane Survey (Hi-GAL) and 850-um observations from the James Clerk Maxwell Telescope (JCMT) to obtain luminosities and masses, respectively, of associated compact sources. The former are infrared luminosities from the catalogue of Elia et al., while the latter are from the JCMT Plane survey source catalogue as well as measurements from new data. The clump-mass distributions of the two regions are found to be consistent with each other, as are the clump-formation efficiency and star-formation efficiency analogues. However, the frequency distributions of the luminosities of the young stellar objects are significantly different. While the luminosity distribution in W51 is consistent with Galaxy-wide samples, that of W49A is top heavy. The differences are not dramatic and are concentrated in the central regions of W49A. However, they suggest that physical conditions there, which are comparable in part to those in extragalactic starbursts, are significantly affecting the star-formation properties or evolution of the dense clumps in the region.
- ID:
- ivo://CDS.VizieR/J/ApJS/240/26
- Title:
- YSO candidates in Canis Major OB1 association
- Short Name:
- J/ApJS/240/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study a very young star-forming region in the outer Galaxy that is the most concentrated source of outflows in the Spitzer Space Telescope GLIMPSE360 survey. This region, dubbed CMa-l224, is located in the Canis Major OB1 association. CMa-l224 is relatively faint in the mid-infrared, but it shines brightly at the far-infrared wavelengths as revealed by the Herschel Space Observatory data from the Hi-GAL survey. Using the 3.6 and 4.5{mu}m data from the Spitzer/GLIMPSE360 survey, combined with the JHKs Two Micron All Sky Survey (2MASS) and the 70-500{mu}m Herschel/Hi-GAL data, we develop young stellar object (YSO) selection criteria based on color-color cuts and fitting of the YSO candidates' spectral energy distributions with YSO 2D radiative transfer models. We identify 293 YSO candidates and estimate physical parameters for 210 sources well fit with YSO models. We select an additional 47 sources with GLIMPSE360-only photometry as "possible YSO candidates." The vast majority of these sources are associated with high H2 column density regions and are good targets for follow-up studies. The distribution of YSO candidates at different evolutionary stages with respect to Herschel filaments supports the idea that stars are formed in the filaments and become more dispersed with time. Both the supernova-induced and spontaneous star formation scenarios are plausible in the environmental context of CMa-l224. However, our results indicate that a spontaneous gravitational collapse of filaments is a more likely scenario. The methods developed for CMa-l224 can be used for larger regions in the Galactic plane where the same set of photometry is available.
- ID:
- ivo://CDS.VizieR/J/MNRAS/468/2325
- Title:
- YSOs in star-forming region associated to V582 Aur
- Short Name:
- J/MNRAS/468/2325
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have studied the environment of the FU Ori type star V582 Aur. Our aim is to explore the star-forming region associated with this young eruptive star. Using slitless spectroscopy, we searched for H{alpha} emission stars within a field of 11.5 arcmin x 11.5 arcmin, centred on V582 Aur. Based on UKIDSS and Spitzer Space Telescope data, we further selected infrared-excess young stellar object candidates. In all, we identified 68 candidate low-mass young stars, 16 of which exhibited H{alpha} emission in the slitless spectroscopic images. The colour-magnitude diagram of the selected objects, based on the IPHAS data, suggests that they are low-mass pre-main-sequence stars associated with the Aur OB 1 association, located at a distance of 1.3kpc from Sun. The bright-rimmed globules in the local environment of V582 Aur probably belong to the dark cloud LDN 1516. Our results suggest that star formation in these globules might have been triggered by the radiation field of a few hot members of Aur OB 1. The bolometric luminosity of V582 Aur, based on archival photometric data and on the adopted distance, is 150-320L_{sun}_.
- ID:
- ivo://CDS.VizieR/J/ApJ/867/151
- Title:
- YSOs in the Gould Belt regions with Gaia-DR2 data
- Short Name:
- J/ApJ/867/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the astrometric results from the Gaia second data release (DR2) for young stellar objects (YSOs) in star-forming regions related to the Gould Belt (GB). These regions are Barnard 59, Lupus 1 to 4, Chamaeleon I and II, {epsilon} Chamaeleontis, the Cepheus flare, IC 5146, and Corona Australis. The mean distance to the YSOs in each region is consistent with earlier estimations, though a significant improvement in the final errors was obtained. The mean distances to the star-forming regions were used to fit an ellipsoid of size (358+/-7)x(316+/-13)x(70+/-4)pc^3^, centered at (X0,Y0,Z0)=(-82+/-15,39+/-7,-25+/-4)pc, consistent with recently determined parameters of the GB. The mean proper motions were combined with radial velocities from the literature to obtain the three- dimensional motions of the star-forming regions, which are consistent with a general expansion of the GB. We estimate that this expansion is occurring at a velocity of 2.5+/-0.1km/s. This is the first time that motions of YSOs have been used to investigate the kinematics of the GB. As an interesting side result, we also identified stars with large peculiar velocities.
