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IC1396A&Trumpler37ClusterChandraX-RayPointSourceCatalog
Rich, young stellar clusters produce H II regions whose expansion into the nearby molecular cloud is thought to trigger the formation of new stars. However, the importance of this mode of star formation is uncertain. This investigation seeks to quantify triggered star formation (TSF) in IC 1396A (aka the Elephant Trunk Nebula), a bright-rimmed cloud (BRC) on the periphery of the nearby giant HII region IC 1396 produced by the Trumpler 37 cluster. X-ray selection of young stars from Chandra X-ray Observatory data is combined with existing optical and infrared surveys to give a more complete census of the TSF population. Over 250 young stars in and around IC 1396A are identified; this doubles the previously known population. A spatio-temporal gradient of stars from the IC 1396A cloud towards the primary ionizing star HD 206267 is found. The current project consists of two Chandra-ACIS X-ray observations of IC 1396A, a Guaranteed Time observation (ObsID No. 11807 obtained on 2010 March 31; PI: Garmire) and a Guest Observer observation (ObsID No. 10990 obtained on 2010 June 9; PI: Getman). Both observations were pointed at the head of the globule but had different roll angles. For each observation, the authors considered only results arising from the imaging array (ACIS-I) of four abutted 1024 x 1024 pixel front-side illuminated charge-coupled devices (CCDs) covering about 17 x 17 arcmin<sup>2</sup> on the sky, Similar to the Chandra catalog of X-ray sources in the Carina Nebula (Broos et al. 2011, ApJS, 194, 2), this list of candidate sources in IC 1396A is trimmed to omit sources with fewer than 3 total source counts (the sum of the net counts and the background counts, NC + BC < 3) and the probability for being a background fluctuation greater than 1% (prob_no_src > 0.01). The final catalog comprises 415 X-ray sources, roughly half of which sources are extragalactic with extremely optically faint counterparts (Section 3.2 of the reference paper), and the rest are young stars associated with the Trumpler 37 and IC 1396A star-forming regions. UVR<sub>c</sub> I<sub>c</sub> observations were carried out with the 1.2-m telescope at the Fred Lawrence Whipple Observatory (FLWO), using the 4Shooter CCD array, between 2000 September and 2002 September. 4Shooter is an array of four CCDs, covering a square of 25 arcminutes on the side. Two 4Shooter fields were taken to cover an ~45 x 25 arcmin<sup>2</sup> area centered on the star HD 206267. The FLWO fields contain the whole ACIS field, except for a small gap in between the four CCDs of 4Shooter. All but a few Chandra stars were observed in 2000 September. UVR<sub>J</sub> I<sub>J</sub> observations of Trumpler 37/IC 1396A were obtained in service mode during three nights in 2007 June 9-11 using the wide-field camera, LAICA, mounted on the 3.5-m telescope in Calar Alto, Spain. LAICA is a 2 x 2 mosaic of four CCDs, each covering a 15.3 x 15.3 arcmin<sup>2</sup> field of view (FOV) with a large gap of 15.3 x 15.3 arcmin<sup>2</sup> in between. The project combines four LAICA pointings covering an ~45 x 45 arcmin<sup>2</sup> area around HD 206267, including nearly the entire ACIS field. The Spitzer observation was obtained on 2003 December 20 with the IRAC detector in all four IRAC channels (3.6, 4.5, 5.8 and 8.0 micron). Two adjacent fields subtending ~37 x 42 arcmin<sup>2</sup> in channel pairs 3.6/5.8 micron and 4.5/8.0 micron were centered on Trumpler 37. To reduce unnecessary data processing the authors analyzed only a portion of the original data that encompassed the Chandra-ACIS field with a coverage of ~19 x 19 arcmin<sup>2</sup> area in all four channels centered on Rim A of the IC 1396A globule. This covers 93% of the ACIS field omitting its north-western and south-western edges. An automated cross-correlation between the Chandra source positions and the optical-IR source positions was made using a search radius of 2 arcseconds within ~6 arcminutes of the ACIS field center, and a
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W 40 Star-Forming Region Chandra X-Ray Point Source Catalog
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The young stellar cluster illuminating the W40 H II region, one of the nearest massive star-forming regions (SFRs), 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. The authors detect 225 X-ray sources, of which 85% are confidently identified as young stellar members of the region. Two potential distances of the cluster, 260 pc and 600 pc, are used in the paper. Supposing the X-ray luminosity function of SFRs to be universal, it supports a 600 pc distance as a lower limit for W40 and a total population of at least 600 stars down to 0.1 Msun under the assumption of a coeval population with a uniform obscuration. In fact, there is strong spatial variation in Ks-band-excess disk fraction and non-uniform obscuration due to a dust lane that is identified in absorption in optical, infrared, and X-ray. The dust lane is likely part of a ring of material which includes the molecular core within W40. In contrast to the likely ongoing star formation in the dust lane, the molecular core is inactive. The star cluster has a spherical morphology, an isothermal sphere density profile, and mass segregation down to 1.5 Msun. However, other cluster properties, including a <= 1 Myr age estimate and ongoing star formation, indicate that the cluster is not dynamically relaxed. X-ray diffuse emission and a powerful flare from a young stellar object are also reported in the reference paper. This table was created by the HEASARC in March 2011 based on electronic versions of Tables, 1, 2 and 4 of the reference paper which were obtained from the ApJ web site. This is a service provided by NASA HEASARC .
IC 1396N Chandra X-Ray Point Source Catalog
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The IC 1396N cometary globule (CG) within the large nearby HII region IC 1396 has been observed with the Advanced CCD Imaging Spectrometer (ACIS) detector on board the Chandra X-Ray Observatory on 2004 October 16.93 to 17.30. 117 X-ray sources are detected, 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. The authors infer a total T Tauri population of ~ 30 stars in the globule, including the undetected population, with a star formation efficiency of 1%-4%. An elongated source spatial distribution with an age gradient oriented toward the exciting star is discovered in the X-ray population of IC 1396N, supporting similar findings in other cometary globules. The geometric and age distribution is consistent with the radiation-driven implosion (RDI) model for triggered star formation in CGs by H II region shocks. The authors include only results arising from the imaging array (ACIS-I) of four abutted 1024 x 1024 pixel front-side illuminated CCDs covering about 17' x 17' on the sky. The aim point of the array was R.A. = 21h40m42.4s, Dec. = +58d1609.7" (J2000.0) or (l,b) = (100.0, + 4.2), and the satellite roll angle (i.e., orientation of the CCD array relative to the north-south direction) was 245.9 degrees. The total net exposure time of the observation is 30 ks with no background flaring due to solar activity or data losses. This table was created by the HEASARC in February 2009 based on the electronic version of Tables 1 and 2 from the paper which were obtained from the CDS (their catalog J/ApJ/654/316 files table1.dat and table2.dat). This is a service provided by NASA HEASARC .
NGC 6357 Chandra X-Ray Point Source Catalog
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This contains some of the results from the first high spatial resolution X-ray study of the massive star-forming region NGC 6357, which were obtained in a 38 ks Chandra/ACIS observation. Inside the brightest constituent of this large H II region complex is the massive open cluster Pismis 24. It contains two of the brightest and bluest stars known, yet remains poorly studied; only a handful of optically bright stellar members have been identified. The authors have investigated the cluster extent and initial mass function and detected ~800 X-ray sources with a limiting sensitivity of ~ 1030 erg s-1: this provides the first reliable probe of the rich intermediate-mass and low-mass population of this massive cluster, increasing the number of known members from optical studies by a factor of ~ 50. The high-luminosity end (log L[2-8 keV] >= 30.3 erg s-1) of the observed X-ray luminosity function in NGC 6357 is clearly consistent with a power-law relation as seen in the Orion Nebula Cluster and Cepheus B, yielding the first estimate of NGC 6357's total cluster population, a few times the known Orion population. The long-standing LX ~ 10-7 Lbol correlation for O stars is confirmed. Twenty-four candidate O stars and one possible new obscured massive YSO or Wolf-Rayet star are presented. Many cluster members are estimated to be intermediate-mass stars from available infrared photometry (assuming an age of ~ 1 Myr), but only a few exhibit K-band excess. The authors report the first detection of X-ray emission from an evaporating gaseous globule at the tip of a molecular pillar; this source is likely a B0-B2 protostar. NGC 6357 was observed on 2004 July 9 with the Imaging Array of the Advanced CCD Imaging Spectrometer (ACIS-I) on board Chandra. Four front-illuminated (FI) CCDs form the ACIS-I, which covers a field of view (FOV) of ~ 17 by 17 arcminutes. The observation was made in the standard Timed Exposure, Very Faint mode, with 3.2 s integration time and 5 pixel by 5 pixel event islands. The total exposure time was 38 ks and the satellite roll angle was 289 degrees. The aim point was centered on the O3 If star Pis 24-1, the heart of the OB association Pismis 24. The Chandra observation ID is 4477. Data reduction started with filtering the Level 1 event list processed by the Chandra X-ray Center pipeline to recover an improved Level 2 event list. To improve absolute astrometry, X-ray positions of ACIS-I sources were obtained by running the wavdetect wavelet-based source detection algorithm within the Chandra Interactive Analysis of Observations (CIAO) package on the original Level 2 event list, using only the central 8 by 8 arcminutes of the field. The resulting X-ray sources were matched to the 2MASS point source catalog. The authors calculated the position offsets between 277 X-ray sources and their NIR counterparts and applied an offset of +0.02" in right ascension (R.A.) and -0.33" in declination to the X-ray coordinates. From an initial list of 910 potential X-ray sources, the authors rejected sources with a PB > 1% likelihood of being a background fluctuation. The trimmed source list includes 779 sources, with full-band (0.5 - 8.0 keV) net (background-subtracted) counts ranging from 1.7 to 1837 counts. The 779 valid sources were purposely divided by the authors into two lists: the 665 sources with PB < 0.1% make up the primary source list of highly reliable sources (Table 1 in the reference paper; sources with source_type = 'M' in this table), and the remaining 114 sources with PB >= 0.1% likelihood of being spurious background fluctuations were listed as tentative sources in Table 2 of the reference paper (source_type = 'T' in this table). The authors believe that most of these tentative sources are likely real detections. This table was created by the HEASARC in October 2007 based on the merger of the electronic versions of Tables
Star Formation in Nearby Clouds (SFiNCs) Probable Cluster Members Catalog
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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 the authors' earlier MYStIX survey of richer, more distant clusters. As a foundation for the SFiNCs science studies, in the reference paper homogeneous data analyses of the Chandra X-ray and Spitzer mid-infrared (MIR) archival SFiNCs data are described, and the resulting catalogs of over 15,300 X-ray and over 1,630,000 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. Sixty-five X-ray observations of the 22 SFiNCs SFRs made with the imaging array on the Advanced CCD Imaging Spectrometer (ACIS) were extracted from the Chandra archive (spanning from 2000 January to 2015 April). See Tables 1 and 2 of the reference paper for the list of SFRs and the log of Chandra ACIS observations, respectively. The final Chandra-ACIS catalog for the 22 SFiNCs SFRs comprises 15,364 X-ray sources (presented in Tables 3 and 4 and section 3.2 of the reference paper, and available as the HEASARC table, SFINCSXRAY). To obtain MIR photometry for X-ray objects and to identify and measure MIR photometry for additional non-Chandra disky stars that were missed in previous studies of the SFiNCs regions (typically faint YSOs), the authors have reduced the archived Spitzer-IRAC data by homogeneously applying the MYStIX-based Spitzer-IRAC data reduction methods of Kuhn et al. (2013, ApJS, 209, 29) to the 423 Astronomical Object Request (AORs) data sets for the 22 SFiNCs SFRs (listed in Table 5 of the reference paper). As in MYStIX, the SFiNCs IRAC source catalog retains all point sources with the photometric signal-to-noise ratio > 5 in both [3.6] and [4.5] um channels. This catalog covers the 22 SFiNCs SFRs and their vicinities on the sky and comprises 1,638,654 IRAC sources with available photometric measurements for 100%, 100%, 29%, and 23% of these sources in the 3.6, 4.5, 5.8, and 8.0um bands, respectively (see table 6 and section 3.4 of the reference paper). Source position cross-correlations between the SFiNCs Chandra X-ray source catalog and an IR catalog, either the "cut-out" IRAC or 2MASS, were made using the steps described in section 3.5 of the reference paper. Using the ensemble of X-ray and infrared data that they have obtained, the authors selected probable YSOs in the 22 SFRs using selection criteria described in section 4.1 of the reference paper. Tables 7 and 8 of the reference paper provide the list of 8,492 SFiNCs probable cluster members (SPCMs: but see below for a caveat on this number) and their main IR and X-ray properties (see section 4 of the reference paper). This present HEASARC table comprises the contents of these two tables. A fuller list of the X-ray properties of the X-ray-detected SPCMs is available in the HEASARC's SFINCSXRAY table (q.v.). This table was created by the HEASARC in September 2017 based on the CDS Catalog J/ApJS/229/28 files table7.dat (the IR photometry of the SFiNCs probable cluster members) and table8.dat (the main X-ray and other properties of the SFiNCs probable cluster members). This is a service provided by NASA HEASARC .
IC 348 Chandra X-Ray Point Source Catalog
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The authors have obtained a deep (53 ks) X-ray image of the very young stellar cluster IC 348 with the Advanced CCD Imaging Spectrometer on board the Chandra X-Ray Observatory. In this image with a sensitivity limit of ~ 1 x 1028 ergs/s (more than 10 times deeper than their ROSAT images of IC 348), 215 X-ray sources were detected. While 115 of these sources can be identified with known cluster members, 58 X-ray sources are most likely new, still unidentified cluster members. About 80% of all known cluster members with masses between ~0.15 and 2 solar masses are visible as X-ray sources in the ACIS image. X-ray emission at levels of ~1028 ergs/s was discovered from four of 13 known brown dwarfs and from three of 12 brown dwarf candidates in IC 348. X-ray emission was also detected from two deeply embedded objects, presumably class I protostars, south of the cluster center. Optical and infrared counterparts have been identified for most of the X-ray sources. Some 40 X-ray sources do not have optical or IR counterparts, and are most likely background (probably extragalactic) objects. This number is consistent with the expected number of extragalactic background X-ray sources based on the observed log N - log S statistics from the deep X-ray counts in the Chandra Deep Field South. This table was created by the HEASARC in January 2007 based on the merger of CDS table J/AJ/122/866/table1.dat (Table 1 from Preibisch and Zinnecker 2001) with the electronic AJ table version of Table 1 from Preibisch and Zinnecker 2002. This is a service provided by NASA HEASARC .
Arches and Quintuplet Clusters Chandra X-Ray Point Source Catalog
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The Galactic centre (GC) provides a unique laboratory for a detailed examination of the interplay between massive star formation and the nuclear environment of our Galaxy. Here are presented some of the results from a 100-ks Chandra Advanced CCD Imaging Spectrometer (ACIS) observation of the Arches and Quintuplet star clusters in the form of a catalog of 244 point-like X-ray sources detected in the observation. The deep Chandra ACIS-I observation (Obs. ID: 4500) was carried out on 2004 June 9. The Arches cluster was placed about 1-arcmin away from the aim point to minimize the effect of the CCD gaps on mapping the extended X-ray emission around the cluster. This table was created by the HEASARC in July 2007 based on CDS Catalog J/MNRAS/371/38 file table1.dat. This is a service provided by NASA HEASARC .
RCW 108 Star Formation Region Chandra X-Ray Point Source Catalog
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This table contains some of the results of an approximately 90 ks 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. The authors detected 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. They find that about 360 of the X-ray sources have near-IR counterparts. They divide the region into five parts based on the X-ray point source characteristics and extended 8 micron emission. The most clearly defined regions are the central region, identified by embedded sources with high luminosities in the both the near-IR and X-ray as well as high X-ray temperatures (~3 keV), and the eastern region, identified by low extinction and ~1 keV X-ray temperatures. Other regions, identified by their directional relationship to RCW 108-IR, are less uniform, representing combinations of the first two regions, independent star formation epochs, or both. The cluster members range in X-ray luminosity from 1029 to 1033 erg s-1. 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. The largest fraction of X-ray sources is best described as possessing some disk material via a more detailed extinction fitting. The authors 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 1021 to 1023 cm-2. They 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. Approximately 800 are confined to the 3' (~1.1 pc) central region. The field was observed by Chandra on 2004 October 25 starting at 02:37 UT for 92.2 ks of total time and 88.8 ks of so-called "good-time" (ObsId 4503). The ACIS was used in the nominal imaging array (chips I0-I3) which provides a field of view of approximately 17' by 17' (~6.5 pc on a side). The aimpoint was at RA, Dec = 16:39:58.7, -48:51:54.4 (J2000.0). In addition, the S2 and S3 chips were on and located over IRAS 16379-4856. About 20 point sources were detected associated with this object; however, the analysis of these data is not presented here because they are far off-axis. This table was created by the HEASARC in June 2008 based on electronic versions of Tables 1, 2, 5, 7, 10 and 11 from the reference paper which were obtained from the Astronomical Journal web site. This is a service provided by NASA HEASARC .
SMC H-Alpha Emission Stars/Nebulae
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This database table contains a list of H-alpha emission-line stars and small nebulae in the Small Magellanic Cloud (SMC) that were discovered in an objective-prism survey. This survey was performed through an H-alpha + [N II] interference filter using the 0.90m Curtis Schmidt telescope at Cerro Tololo Inter-American Observatory (CTIO). 1898 emission-line objects were detected in the main body of the SMC, almost quadrupling the number of those discovered in previous objective-prism surveys of the same region. Among these 1898 objects are newly discovered planetary nebulae, compact H II regions, and late-type stars. Continuum intensities, the shapes and strengths of the H-alpha emission line, co-ordinates and (where available) cross-identifications are provided for the listed objects. This version of the SMC H-alpha Emission-Line Stars and Small Nebulae Catalog of Meyssonnier and Azzopardi was created by the HEASARC in November 1997 based on the ADC/CDS machine-readable catalog J/A+AS/102/451. This is a service provided by NASA HEASARC .
Star Formation in Nearby Clouds (SFiNCs) X-Ray Source Catalog
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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, in the reference paper homogeneous data analyses of the Chandra X-ray and Spitzer mid-infrared archival SFiNCs data are described, and the resulting catalogs of over 15,300 X-ray and over 1,630,000 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. Sixty-five X-ray observations of the 22 SFiNCs SFRs made with the imaging array on the Advanced CCD Imaging Spectrometer (ACIS) were extracted from the Chandra archive (spanning from 2000 January to 2015 April). See Tables 1 and 2 of the reference paper for the list of SFRs and the log of Chandra ACIS observations, respectively. The final Chandra-ACIS catalog for the 22 SFiNCs SFRs comprises 15,364 X-ray sources (presented in Tables 3 and 4 and section 3.2 of the reference paper, and the contents of this HEASARC table, SFINCSXRAY). To obtain MIR photometry for X-ray objects and to identify and measure MIR photometry for additional non-Chandra disky stars that were missed in previous studies of the SFiNCs regions (typically faint YSOs), the authors have reduced the archived Spitzer-IRAC data by homogeneously applying the MYStIX-based Spitzer-IRAC data reduction methods of Kuhn et al. (2013, ApJS, 209, 29) to the 423 Astronomical Object Request (AORs) data sets for the 22 SFiNCs SFRs (Table 5 of the reference paper). As in MYStIX, the SFiNCs IRAC source catalog retains all point sources with the photometric signal-to-noise ratio > 5 in both [3.6] and [4.5] um channels. This catalog covers the 22 SFiNCs SFRs and their vicinities on the sky and comprises 1,638,654 IRAC sources with available photometric measurements for 100%, 100%, 29%, and 23% of these sources in the 3.6, 4.5, 5.8, and 8.0um bands, respectively (see table 6 and section 3.4 of the reference paper). Source position cross-correlations between the SFiNCs Chandra X-ray source catalog and an IR catalog, either the "cut-out" IRAC or 2MASS, were made using the steps described in section 3.5 of the reference paper. Tables 7 and 8 of the reference paper provide the list of 8,492 SFiNCs probable cluster members (SPCMs) and their main IR and X-ray properties (see section 4 of the reference paper): this list as available at the HEASARC as the SFINCSPCM table (q.v.). This table was created by the HEASARC in September 2017 based on the CDS Catalog J/ApJS/229/28 files table3.dat (the list of SFiNCs X-ray sources and their basic properties) and table4.dat (the list of SFiNCs X-ray source fluxes). This is a service provided by NASA HEASARC .
NGC 2024 Chandra X-Ray Point Source Catalog
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The NGC 2024 Chandra X-Ray Point Source Catalog contains the results of a sensitive 76 ks Chandra observation of the young stellar cluster in NGC 2024, lying at a distance of ~415 pc in the Orion B giant molecular cloud. Previous infrared observations have shown that this remarkable cluster contains several hundred embedded young stars, most of which are still surrounded by circumstellar disks. Thus, it presents a rare opportunity to study X-ray activity in a large sample of optically invisible protostars and classical T Tauri stars (CTTSs) undergoing accretion. Chandra detected 283 X-ray sources, of which 248 were identified with counterparts at other wavelengths, mostly in the near-infrared. Astrometric registration of Chandra images against the Two Micron All Sky Survey (2MASS) resulted in positional offsets of ~0.25" near field center, yielding high confidence identifications of infrared counterparts. The Chandra detections are characterized by hard, heavily absorbed spectra and specular variability. Spectral analysis of more than 100 of the brightest X-ray sources yields a mean V-band extinction of ~10.5 magnitudes and typical plasma energies ~ 3 keV. Chandra detected all but one of a sample of 27 classical T Tauri stars (CTTSs) identified from previous near- and mid-infrared photometry, and their X-ray and bolometric luminosities are correlated. IRS 2b, which is thought to be a massive embedded late O or early B star that may be the ionizing source of NGC 2024, is detected as an X-ray source. Seven millimeter-bright cores (FIR 1-7) in NGC 2024 that may be protostellar were not detected, with the possible exception of faint emission near the unusual core FIR 4. This table was created by the HEASARC in January 2007 based on CDS table J/ApJ/598/375/table1.dat. This is a service provided by NASA HEASARC .
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