- ID:
- ivo://CDS.VizieR/J/AJ/132/1100
- Title:
- X-ray and IR sources in RCW 38
- Short Name:
- J/AJ/132/1100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on results of a 96.7ks Chandra observation of one of the youngest, most embedded, and most massive young stellar clusters studied in X-rays: RCW 38. We detect 460 sources in the field, of which 360 are confirmed to be associated with the RCW 38 cluster. The cluster members range in luminosity from 10^30^ to 10^33.5^ergs/s. Over 10% of the cluster members with over 100 counts exhibit flares, while about 15% of the cluster members with over 30 counts are variable. Of the sources identified as cluster members, 160 have near-infrared (NIR) counterparts either in the Two Micron All Sky Survey database or detected via Very Large Telescope observations. Of these, about 20% appear to have optically thick disks. An additional 353 members are identified through NIR observations, of which at least 50% possess optically thick disks. We fit over 100 X-ray sources as absorbed Raymond-Smith-type plasmas and find that the column to the cluster members varies from 10^21.5^ to 10^23^cm^-2^. We compare the gas to dust absorption signatures in these stars and find NH=A_V_(2x10^21^)cm^-2^. We find that the cluster contains 31 candidate OB stars and is centered about 10" (0.1pc) west of the primary source of the ionization, the O5 star IRS 2. The cluster has a peak central density of about 400 X-ray sources/pc^2^. We estimate that the total cluster membership exceeds 2000 stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/135/693
- Title:
- X-ray and IR sources in RCW 108
- Short Name:
- J/AJ/135/693
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the results of an approximately 90ks Chandra observation of a complex region that hosts multiple sites of recent and active star formation in ARA OB1a. The field is centered on the embedded cluster RCW 108-IR and includes a large portion of the open cluster NGC 6193. We detect over 420 X-ray sources in the field and combined these data with deep near-IR, Spitzer/IRAC and Midcourse Space Experiment (MSX) mid-IR data. We find about 360 of the X-ray sources have near-IR counterparts. We divide the region into five parts based on the X-ray point source characteristics and extended 8um emission. The most clearly defined regions are the central region, identified by embedded sources with high luminosities in both the near-IR and X-ray as well as high X-ray temperatures (~3keV), and the eastern region, identified by low extinction and ~1keV X-ray temperatures. The cluster members range in X-ray luminosity from 10^29^ to 10^33^erg/s. Over 18% of the cluster members with over 100 counts exhibit flares. All sources with over 350 counts are variable. Overall about 10% (16% in RCW 108-IR) appear to have optically thick disks as derived from their position in the (J-H), (H-K) diagram. The disk fraction becomes much higher when IRAC data are employed. We fit the bulk of the X-ray spectra as absorbed Raymond-Smith-type plasmas, and find that the column to the RCW 108-IR members varies from 10^21^ to 10^23^cm^-2^. We find that the field contains 41 candidate O or B stars, and estimate that the total number of pre-main-sequence stars in the field is about 1600+/-200.
- ID:
- ivo://CDS.VizieR/J/ApJ/665/719
- Title:
- X-ray imaging of RCW 49
- Short Name:
- J/ApJ/665/719
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a high-resolution X-ray imaging study of the stellar population in the Galactic massive star-forming region RCW 49 and its central OB association Westerlund 2. We obtained a ~40ks X-ray image of a ~17'x17' field using the Chandra X-Ray Observatory and deep NIR images using the Infrared Survey Facility in a concentric ~8.3'x8.3' region. We detected 468 X-ray sources and identified optical, NIR, and Spitzer MIR counterparts for 379 of them.
- ID:
- ivo://CDS.VizieR/J/ApJ/562/446
- Title:
- X-rays and protostars in Trifid nebula
- Short Name:
- J/ApJ/562/446
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Trifid Nebula is a young HII region, recently rediscovered as a "pre-Orion" star-forming region, containing protostars undergoing violent mass ejections visible in optical jets as seen in images from the Infrared Space Observatory and the Hubble Space Telescope. We report the first X-ray observations of the Trifid Nebula using ROSAT and ASCA. The ROSAT image shows a dozen X-ray sources, with the brightest X-ray source being the O7 star, HD 164492, which provides most of the ionization in the nebula. We also identify 85 T Tauri star and young, massive star candidates from near-infrared colors using the JHKs color-color diagram from the Two-Micron All-Sky Survey (2MASS). Ten X-ray sources have counterpart near-infrared sources. The 2MASS stars and X-ray sources suggest there are potentially numerous protostars in the young HII region of the Trifid. ASCA moderate-resolution spectroscopy of the brightest source shows hard emission up to 10keV with a clearly detected FeK line.
- ID:
- ivo://CDS.VizieR/J/ApJ/725/2485
- Title:
- X-rays from the star-forming complex W40
- Short Name:
- J/ApJ/725/2485
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The young stellar cluster illuminating the W40 HII region, one of the nearest massive star-forming regions, has been observed with the ACIS detector on board the Chandra X-ray Observatory. Due to its high obscuration, this is a poorly studied stellar cluster with only a handful of bright stars visible in the optical band, including three OB stars identified as primary excitation sources. We detect 225 X-ray sources, of which 85% are confidently identified as young stellar members of the region. Two potential distances of the cluster, 260pc and 600pc, are used in the paper.
- ID:
- ivo://CDS.VizieR/J/ApJ/654/316
- Title:
- X-ray sources in IC 1396N
- Short Name:
- J/ApJ/654/316
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The IC 1396N cometary globule (CG) within the large nearby HII region IC 1396 has been observed with the ACIS detector on board the Chandra X-Ray Observatory. We detect 117 X-ray sources, of which ~50-60 are likely members of the young open cluster Trumpler 37 dispersed throughout the HII region, and 25 are associated with young stars formed within the globule. Infrared photometry (2MASS and Spitzer) shows that the X-ray population is very young: 3 older Class III stars, 16 classical T Tauri stars, and 6 protostars including a Class 0/I system.
- ID:
- ivo://CDS.VizieR/J/AJ/131/2164
- Title:
- X-ray sources in RMC 136
- Short Name:
- J/AJ/131/2164
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have studied the X-ray point-source population of the 30 Doradus (30 Dor) star-forming complex in the Large Magellanic Cloud using high spatial resolution X-ray images and spatially resolved spectra obtained with the Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra X-Ray Observatory. Here we describe the X-ray sources in a 17'x17' field centered on R136, the massive star cluster at the center of the main 30 Dor nebula. We detect 20 of the 32 Wolf-Rayet stars in the ACIS field. The cluster R136 is resolved at the subarcsecond level into almost 100 X-ray sources, including many typical O3-O5 stars, as well as a few bright X-ray sources previously reported.
- ID:
- ivo://CDS.VizieR/J/A+A/602/A115
- Title:
- X-ray survey of NGC7000/IC5070
- Short Name:
- J/A+A/602/A115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first extensive X-ray study of the North-America and Pelican star-forming region (NGC7000/IC5070), with the aim of finding and characterizing the young population of this cloud. X-ray data from Chandra (four pointings) and XMM-Newton (seven pointings) were reduced and source detection algorithm applied to each image. We complement the X-ray data with optical and near-IR data from the IPHAS, UKIDSS, and 2MASS catalogs, and with other published optical and Spitzer IR data. More than 700 X-ray sources are detected, the majority of which have an optical or NIR counterpart. This allowed us to identify young stars in different stages of formation. Less than 30% of X-ray sources are identified with a previously known young star. We argue that most X-ray sources with an optical or NIR counterpart, except perhaps for a few tens at near-zero reddening, are likely candidate members of the star-forming region, on the basis of both their optical and NIR magnitudes and colors, and of X-ray properties such as spectrum hardness or flux variations. They are characterized by a wide range of extinction, and sometimes near-IR excesses, both of which prevent derivation of accurate stellar parameters. The optical color-magnitude diagram suggests ages between 1-10Myrs. The X-ray members have a very complex spatial distribution with some degree of subclustering, qualitatively similar to that of previously known members. The detailed distribution of X-ray sources relative to the objects with IR excesses identified with Spitzer is sometimes suggestive of sequential star formation, especially near the 'Gulf of Mexico' region, probably triggered by the O5 star which illuminates the whole region. We confirm that around the O5 star no enhancement in the young star density is found, in agreement with previous results. Thanks to the precision and depth of the IPHAS and UKIDSS data used, we also determine the local optical-IR reddening law, and compute an updated reddening map of the entire region.
- ID:
- ivo://CDS.VizieR/J/AJ/139/1066
- Title:
- X-ray view of NGC 2403 central region
- Short Name:
- J/AJ/139/1066
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Archival Chandra observations are used to study the X-ray emission associated with star formation in the central region of the nearby SAB(s)cd galaxy NGC 2403. The distribution of X-ray emission is compared to the morphology visible at other wavelengths using complementary Spitzer, Galaxy Evolution Explorer, and ground-based H{alpha} imagery.
- ID:
- ivo://CDS.VizieR/J/ApJ/695/511
- Title:
- Young massive stars in LHA 120-N 44
- Short Name:
- J/ApJ/695/511
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The HII complex N44 in the Large Magellanic Cloud (LMC) provides an excellent site to perform a detailed study of star formation in a mild starburst, as it hosts three regions of star formation at different evolutionary stages, and it is not as complicated and confusing as the 30 Doradus giant HII region. We have obtained Spitzer Space Telescope observations and complementary ground-based 4m uBVIJK observations of N44 to identify candidate massive young stellar objects (YSOs). We further classify the YSOs into Types I, II, and III, according to their spectral energy distributions (SEDs). In our sample of 60 YSO candidates, ~65% of them are resolved into multiple components or extended sources in high-resolution ground-based images.
