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IC1396ACXO - IC 1396A & Trumpler 37 Cluster Chandra X-Ray Point Source Catalog

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Overview

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 arcmin2 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.

UVRc Ic 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 arcmin2 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. UVRJ IJ 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 arcmin2 field of view (FOV) with a large gap of 15.3 x 15.3 arcmin2 in between. The project combines four LAICA pointings covering an ~45 x 45 arcmin2 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 arcmin2 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 arcmin2 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 search radius of 3.5 arcseconds in the outer regions of the ACIS field where the X-ray source positions are more uncertain due to the deterioration of the Chandra telescope PSF. This was followed by a careful visual examination of each source in both bands to remove dubious sources and associations.


Catalog Bibcode

2012MNRAS.426.2917G

References

The Elephant Trunk Nebula and the Trumpler 37 cluster: contribution of triggered
star formation to the total population of an HII region.
    Getman K.V., Feigelson E.D., Sicilia-Aguilar A., Broos P.S., Kuhn M.A.,
    Garmire G.P.
   <Mon. Not. R. Astron. Soc., 426, 2917-2943 (2012)>
   =2012MNRAS.426.2917G

Provenance

This table was created by the HEASARC in April 2017 based upon the CDS Catalog J/MNRAS/426/2917 files table1.dat, table2.dat, and table3.dat.

Parameters

Source_Number
A unique identification source number for the detected sources, listed in order of increasing J2000.0.

Name
The primary source designation in the style recommended by the Dictionary of Nomenclature of Celestial Objects, using the prefix 'CXOIC1396A' for Chandra X-ray Observatory IC 1396A and the J2000.0 Right Ascension and Declination truncated to 0.01 seconds of time in RA and to 0.1 arcseconds in Declination, viz., 'CXOIC1396A JHHMMSS.ss+DDMMSS.s'.

RA
The Right Ascension of the Chandra X-ray source in the selected equinox. This was given in J2000.0 equatorial coordinates to a precision of 10-6 degrees in the original table.

Dec
The Declination of the Chandra X-ray source in the selected equinox. This was given in J2000.0 equatorial coordinates to a precision of 10-6 degrees in the original table.

LII
The Galactic Longitude of the Chandra X-ray source.

BII
The Galactic Latitude of the Chandra X-ray source.

Error_Radius
The 1-sigma (~68% confidence level) positional uncertainty of the Chandra X-ray source, in arcseconds.

Off_Axis
The average off-axis angle in units of arcminutes, which is the separation between the source position and the aim point of the two merged observations.

Counts
The source net counts in the merged apertures in the 0.5-8 keV band.

Counts_Error
The 1-sigma upper uncertainty in the source net counts in the 0.5-8.0 keV band.

Bck_Counts
The observed background counts in the merged apertures for the Chandra X-ray source in the 0.5-8.0 keV band.

PSF_Fraction
The average PSF fraction for the merged observations (at 1.5 keV) contained within the source aperture.

Prob_No_Src_Min
The smallest of the three p-values for the full (0.5-8.0 keV), soft (0.5-2.0 keV) and hard (2.0-8.0 keV) bands for the no-source hypothesis, where p is the PbNoSrc parameter of Broos et al. 2010, ApJ, 714, 1582, their Section 4.3 and Appendix B).

Exposure
The effective exposure time at the position of the X-ray source, in seconds (converted by the HEASARC from the ks units used in the original table).

Prob_Constant_Intra_Min
The smallest p-value for the one-sample K-S statistic under the no variability null hypothesis within a single observation.

Prob_Constant_Inter_Min
The p-value for the one-sample K-S statistic under the no variability null hypothesis over the combined observations.

Median_Energy
The median energy of the Chandra X-ray source in the 0.5-8 keV band, in keV.

Photon_Flux
The apparent photometric flux of the Chandra X-ray source in the 0.5-8 keV band, in photon cm-2 s-1.

Vmag_1
The V magnitude of the optical counterpart to the Chandra X-ray source as measured in the FLWO observations.

Vmag_1_Error
The uncertainty in the corresponding magnitude of the optical counterpart to the Chandra X-ray source.

Imag_1
The IC magnitude of the optical counterpart to the Chandra X-ray source as measured in the FLWO observations.

Imag_1_Error
The uncertainty in the corresponding magnitude of the optical counterpart to the Chandra X-ray source.

Vmag_2
The V magnitude of the optical counterpart to the Chandra X-ray source as measured in the LAICA observations.

Vmag_2_Error
The uncertainty in the corresponding magnitude of the optical counterpart to the Chandra X-ray source.

Imag_2
The IJ magnitude of the optical counterpart to the Chandra X-ray source as measured in the LAICA observations.

Imag_2_Error
The uncertainty in the corresponding magnitude of the optical counterpart to the Chandra X-ray source.

Jmag
The J magnitude of the infrared counterpart to the Chandra X-ray source as listed in the 2MASS Catalog.

Jmag_Error
The uncertainty in the corresponding magnitude of the infrared counterpart to the Chandra X-ray source.

Hmag
The H magnitude of the infrared counterpart to the Chandra X-ray source as listed in the 2MASS Catalog.

Hmag_Error
The uncertainty in the corresponding magnitude of the infrared counterpart to the Chandra X-ray source.

Ks_Mag
The Ks magnitude of the infrared counterpart to the Chandra X-ray source as listed in the 2MASS Catalog.

Ks_Mag_Error
The uncertainty in the corresponding magnitude of the infrared counterpart to the Chandra X-ray source.

TwoMASS_Flags
The 2MASS photometry quality and confusion/contamination flags (see CDS Cat. II/246 for a detailed explanation of their meaning).

IRAC_3p6_um_Mag
The Spitzer/IRAC 3.6-um magnitude of the infrared counterpart to the Chandra X-ray source.

IRAC_3p6_um_Mag_Error
The uncertainty in the corresponding magnitude of the infrared counterpart to the Chandra X-ray source.

IRAC_4p5_um_Mag
The Spitzer/IRAC 4.5-um magnitude of the infrared counterpart to the Chandra X-ray source.

IRAC_4p5_um_Mag_Error
The uncertainty in the corresponding magnitude of the infrared counterpart to the Chandra X-ray source.

IRAC_5p8_um_Mag
The Spitzer/IRAC 5.8-um magnitude of the infrared counterpart to the Chandra X-ray source.

IRAC_5p8_um_Mag_Error
The uncertainty in the corresponding magnitude of the infrared counterpart to the Chandra X-ray source.

IRAC_8p0_um_Mag
The Spitzer/IRAC 8.0-um magnitude of the infrared counterpart to the Chandra X-ray source.

IRAC_8p0_um_Mag_Error
The uncertainty in the corresponding magnitude of the infrared counterpart to the Chandra X-ray source.

IRAC_Quality_Flag
A digital flag coding the IRAC photometric apertures and the source contamination level as follows:

    2 = 2-pixel (1.73") aperture with possible contaminating flux from a
        neighboring source of no more than 10%;
   2c = 2-pixel (1.73") apertures with possible contaminating flux of >10%;
    3 = 3-pixel (2.6") aperture with possible contaminating flux from a
        neighboring source of no more than 5%;
    4 = 4-pixel (3.46") apertures with possible contaminating flux from a
        neighboring source of no more than 5%.
  

Log_NH
The logarithm of the absorbing column density NH in atom cm-2 for the Chandra X-ray source..

Log_NH_Error
The uncertainty in the absorbing X-ray column density NH in atom cm-2, summing in quadrature the statistical and systematic errors.

Log_Lx
The logarithm of the intrinsic X-ray luminosity of the Chandra source in the full (0.5-8.0 keV) band, in erg s-1. Luminosities are derived assuming that the source is at the distance of 870 pc for this star formation region.

Log_Lx_Error
The uncertainty in the logarithm of the intrinsic X-ray luminosity of the Chandra source in the full (0.5-8.0 keV) band, in erg s-1, summing in quadrature the statistical and systematic errors.

Age_1_Limit
This parameter is set to '>' if the corresponding age estimate is a lower limit.

Age_1
The age in Myr estimated for the source derived from its position in the optical V versus V-IC color-magnitude diagram using the FLWO data and the pre-main sequence (PMS) models of Siess, Dufour & Forestini (2000, A&A, 358, 593) and assuming a constant source extinction for the optical PMS candidates of AV = 1.56 mag (Sicilia-Aguilar et al. 2005, AJ, 130, 188; Barentsen et al. 2011, MNRAS, 415, 103).

Age_2_Limit
This parameter is set to '>' if the corresponding age estimate is a lower limit.

Age_2
The age in Myr estimated for the source derived from its position in the optical V versus V-IJ color-magnitude diagram using the LAICA data and the pre-main sequence (PMS) models of Siess, Dufour & Forestini (2000, A&A, 358, 593) and assuming a constant source extinction for the optical PMS candidates of AV = 1.56 mag (Sicilia-Aguilar et al. 2005, AJ, 130, 188; Barentsen et al. 2011, MNRAS, 415, 103).

IR_Spectral_Index
The apparent (not dereddened) slope of the infrared SED, alpha0, of the source, obtained from a least-squares linear fit to the log(lambda x Flambda) values in the specified number of IRAC wavelength bands.

IR_Spectral_Index_Error
The 1-sigma uncertainty in the apparent (not dereddened) slope of the infrared SED, alpha0, of the source.

Num_IRAC_Bands
The number of IRAC bands from which the SED slope was derived.

TwoMASS_Name
The name of the 2MASS counterpart to the Chandra X-ray source.

IRAC_Name
The source identifier from the authors' IRAC data analysis, using the HEASARC-created prefix of '[GFS2012] IRAC' for 'Getman, Feigelson, Sicilia-Aguilar 2012 IRAC' in the style recommended by the Dictionary of Nomenclature of Celestial Objects.

IRAC_FOV_Flag
This flag is set to 'O' to indicate that the position of the X-ray source lies outside of the field of view of the IRAC data analysis.

SA05_Source_Number
The identifier (NN-NNNN) of the stellar counterpart to the Chandra X-ray source in Sicilia-Aguilar et al. (2005, AJ, 130, 188). The full name of such objects in Simbad is '[SHB2004] Trumpler 37 NN-NNNN'.

B11_Source_Number
The identifier (NNN) of the stellar counterpart to the Chandra X-ray source in Barentsen et al. (2011, MNRAS, 415, 103). The full name of such objects in Simbad is '[BVD2011] NNN'.

MC09_Source_Number
The identifier (NN) of the stellar counterpart to the Chandra X-ray source in Morales-Calderon et al. (2009, ApJ, 702, 1507). The full name of such objects in Simbad is '[MSR2009] IC1396A-NN'.

Globule_Flag
This binary flag indicates whether the X-ray source lies projected against the IC 1396A globule (set to 1) or not (set to 0).

Broad_Type
This parameter contains information on the source membership and young stellar object (YSO) classification, as follows:

     EXG = possible extragalactic contaminant;
     FRG = possible foreground contaminant or YSO;
     DSK = "disky" YSOs;
     NOD = diskless YSOs;
    UNC1 = object of the uncertain class, with no IR counterparts; these are
            most likely extragalactic objects but some can be background stars;
    UNC2 = object of the uncertain class, having weak registered and unregistered
            IR counterparts or lie close to bright IR objects; these could be
            YSOs or field stars or extragalactic objects.
  

Contact Person

Questions regarding the IC1396ACXO database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 11-Apr-2017