J/ApJ/716/474 The Rosette star-forming complex. III. (Wang+, 2010)
A Chandra study of the Rosette star-forming complex. III. The NGC 2237 cluster and the regions star formation history Wang J., Feigelson E.D., Townsley L.K., Broos P.S., Roman-Zuniga C.G., Lada E., Garmire G. <Astrophys. J., 716, 474-489 (2010)> =2010ApJ...716..474W
ADC_Keywords: X-ray sources ; Cross identifications ; Clusters, open ; Stars, pre-main sequence ; YSOs Keywords: ISM: individual objects (Rosette Nebula) - open clusters and associations: individual (NGC 2237, NGC 2244) - stars: formation - stars: pre-main sequence - X-rays: stars Abstract: We present high spatial resolution Chandra X-ray images of the NGC 2237 young stellar cluster on the periphery of the Rosette Nebula. We detect 168 X-ray sources, 80% of which have stellar counterparts in USNO, Two Micron All Sky Survey, and deep FLAMINGOS images. These constitute the first census of the cluster members with 0.2≲M≲2M☉. Star locations in near-infrared color-magnitude diagrams indicate a cluster age around 2Myr with a visual extinction of 1≲AV≲3 at 1.4kpc, the distance of the Rosette Nebula's main cluster NGC 2244. We derive the K-band luminosity function and the X-ray luminosity function of the cluster, which indicate a population ∼400-600 stars. The X-ray-selected sample shows a K-excess disk frequency of 13%. The young Class II counterparts are aligned in an arc ∼3pc long suggestive of a triggered formation process induced by the O stars in NGC 2244. The diskless Class III sources are more dispersed. Several X-ray emitting stars are located inside the molecular cloud and around gaseous pillars projecting from the cloud. This X-ray view of young stars on the western side of the Rosette Nebula complements our earlier studies of the central cluster NGC 2244 and the embedded clusters on the eastern side of the Nebula. The large-scale distribution of the clusters and molecular material is consistent with a scenario in which the rich central NGC 2244 cluster formed first, and its expanding HII region triggered the formation of the now-unobscured satellite clusters Rosette Molecular Cloud (RMC) XA and NGC 2237. A large swept-up shell material around the HII region is now in a second phase of collect-and-collapse fragmentation, leading to the recent formation of subclusters. Description: The NGC 2237 region was observed with the Imaging Array of the Chandra Advanced CCD Imaging Spectrometer (ACIS-I) which has a field of view ∼17'x17'. The 20ks ACIS-I observation was conducted on 2007 February 9. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 104 130 Primary Chandra catalog: X-ray source properties table2.dat 104 38 Tentative Chandra catalog: X-ray source properties table3.dat 101 63 X-ray spectroscopy table4.dat 109 168 Stellar counterparts
See also: B/chandra : The Chandra Archive Log (CXC, 1999-2012) II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) I/284 : The USNO-B1.0 Catalog (Monet+ 2003) J/ApJ/696/47 : Chandra study of Rosette complex. II. (Wang+, 2009) J/ApJ/675/464 : Chandra observations of NGC 2244 (Wang+, 2008) J/A+A/384/890 : BVRIHa photometry of NGC 2244 X-ray stars (Berghoefer+, 2002) J/ApJ/454/151 : OB Associations of the Northern Milky Way (Massey+ 1995) J/ApJ/428/693 : Rosette Nebula and Maddalena Cloud structures (Williams+ 1994) Byte-by-byte Description of file: table.dat
Bytes Format Units Label Explanations
1- 3 I3 --- Seq [1/168] Running sequence number; sorted by RA (G1) 5- 22 A18 --- CXOU IAU designation (HHMMSS.ss+DDMMSS.s; J2000) (G1) 24- 32 F9.6 deg RAdeg Right Ascension in decimal degrees (J2000) 34- 41 F8.6 deg DEdeg Declination in decimal degrees (J2000) 43- 45 F3.1 arcsec sigma Estimated random component of position error (1) 47- 50 F4.1 arcmin theta Off-axis angle 52- 56 F5.1 ct Ct Estimated net 0.5-8 keV counts 58- 61 F4.1 ct e_Ct Poisson-based 1σ error in Ct 63- 66 F4.1 ct Bt Background 0.5-8 keV counts 68- 71 F4.1 ct Ch Estimated net 2-8 keV counts 73- 76 F4.2 --- PSF PSF fraction enclosed within extraction region (2) 78- 81 F4.1 --- Sig Photometric significance (3) 83 A1 --- l_logPB Limit flag on logPB 84- 88 F5.1 [-] logPB Log probability of not-real source (4) 90- 93 A4 --- Anom Source anomalies (5) 95 A1 --- Var [a-c ] Variability characterization (6) 97-100 F4.1 ks Exp Effective exposure time (7) 102-104 F3.1 keV Emed Background-corrected median photon energy (0.5-8 keV)
Note (1): 1σ, computed as (standard deviation of PSF inside extraction region)/(# of counts extracted)0.5. Note (2): At 1.497 keV. Note that a reduced PSF fraction (significantly below 90%) may indicate that the source is in a crowded region. Note (3): Computed as (net counts)/(upper error on net counts). Note (4): That extracted counts (0.5-8keV) are solely from background. Some sources have PB values above the 1% threshold that defines the catalog because local background estimates can rise during the final extraction iteration after sources are removed from the catalog. Note (5): Anomalies flag as follows: g = fractional time that source was on a detector (FRACEXPO from mkarf) is <0.9; e = source on field edge; p = source piled up; s = source on readout streak. Note (6): Based on the Kolmogorov-Smirnov statistic in the total band as follows: a = no evidence for variability (0.05<PKS); b = possibly variable (0.005<PKS<0.05); c = definitely variable (PKS<0.005). No value is reported for sources with fewer than 4 counts or for sources in chip gaps or on field edges. Note (7): Approximate time the source would have to be observed on axis to obtain the reported number of counts.
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 3 I3 --- Seq [2/168] Running sequence number (G1) 5- 22 A18 --- CXOU IAU designation (HHMMSS.ss+DDMMSS.s; J2000) (G1) 24- 28 F5.1 ct Ct Estimated net 0.5-8 keV counts 30- 33 F4.1 --- Sig Photometric significance (1) 35- 38 F4.1 [cm-2] logNH Log of hydrogen column density (2) 39 A1 --- f_logNH [*] *: value was frozen in the fit 41- 43 F3.1 [cm-2] e_logNH ? Lower 90% confidence interval in logNH (3) 45- 47 F3.1 [cm-2] E_logNH ? Upper 90% confidence interval in logNH (3) 49- 52 F4.1 keV kT Plasma temperature (2) 53 A1 --- f_kT [*] *: value was frozen in the fit 55- 57 F3.1 keV e_kT ? Lower 90% confidence interval in kT (3) 59- 61 F3.1 keV E_kT ? Upper 90% confidence interval in kT (3) 63- 66 F4.1 [cm-3] logEM Log of emission measure; distance=1.4kpc (2) 68- 71 F4.2 [cm-3] e_logEM ? Lower 90% confidence interval in logEM (3) 73- 76 F4.2 [cm-3] E_logEM ? Upper 90% confidence interval in logEM (3) 78- 81 F4.1 [10-7W] logLs ? Log of 0.5-2 keV luminosity (4) 83- 86 F4.1 [10-7W] logLh Log of 2-8 keV luminosity 88- 91 F4.1 [10-7W] logLhc Log of absorption-corrected 2-8 keV luminosity 93- 96 F4.1 [10-7W] logLt Log of 0.5-8 keV luminosity 98-101 F4.1 [10-7W] logLtc ? Log of absorption-corrected 0.5-8 keV luminosity (4)
Note (1): Computed as (net counts)/(upper error on net counts). Note (2): In four cases (19, 113, 162 and 163), a powerlaw spectral model gives a significantly better fit than a single-temperature thermal model. In these cases, kT is the powerlaw index Γ and logEM is the normalization of the spectrum. Note (3): Uncertainties are missing when XSPEC was unable to compute them or when their values were so large that the parameter is effectively unconstrained. Fits lacking uncertainties, fits with large uncertainties, and fits with frozen parameters should be viewed merely as splines to the data to obtain rough estimates of luminosities; the listed parameter values are unreliable. Note (4): Omitted when logNH>22.5 since the soft band emission is essentially unmeasurable.
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 3 I3 --- Seq [1/168] Running sequence number (G1) (1) 5- 22 A18 --- CXOU IAU designation (HHMMSS.ss+DDMMSS.s; J2000) (G1) 24- 35 A12 --- USNO USNO B1.0 identification 37- 41 F5.2 mag Bmag ? The B band magnitude (2) 43- 47 F5.2 mag Rmag ? The R band magnitude (2) 49- 53 F5.2 mag Imag ? The I band magnitude (2) 55- 70 A16 --- 2MASS 2MASS identification (HHMMSSss+DDMMSSs; J2000) 72- 84 A13 --- FLAM FLAMINGOS identification (HHMMSS+DDMMSS) (G1) 86- 90 F5.2 mag Jmag ? The J band magnitude (2) 92- 96 F5.2 mag Hmag ? The H band magnitude (2) 98-102 F5.2 mag Ksmag ? The K_S_ band magnitude (2) 104-109 A6 --- PhFlg [A-U0c] Photometry flag (Qflg and Cfgl of Cat. II/246)
Note (1): For convenience: [OI81] = Ogura & Ishida (1981PASJ...33..149O; <NGC 2244 NNN> in Simbad), [MJD95] = Massey, Johnson, & Degioia-Eastwood (1995, Cat. J/ApJ/454/151; <[MJD95] JHHMMSS.ss+DDMMSS.s> in Simbad ), [BC02] = Berghofer & Christian (2002, Cat. J/A+A/384/890; <[BC2002] NNN> in Simbad). 53 = [OI81] 14 = [MJD95] 104; spectral type B1V; pmRA=11.0mas/yr, pmDE=-2.8mas/yr; 54 = [OI81] 10 = [MJD95] 108; spectral type B2V; pmRA=-2.3mas/yr, pmDE=-11.9mas/yr; 61 = V539 Mon [OI81] 13 = [MJD95] 110; MSX6C G206.1821-02.3456; pmRA=2.8mas/yr, pmDE=0.4mas/yr; 71 = [OI81] 12 = [MJD95] 102; pmRA=6.8mas/yr, pmDE=0.6mas/yr; 128 = [OI81] 35 = [MJD95] 471; spectral type A2:; pmRA=-0.8mas/yr, pmDE=3.6mas/yr; 138 = [OI81] 36 = [MJD95] 497; spectral type B5; pmRA=6.5mas/yr, pmDE=2.1mas/yr; 141 = [MJD95] 498; pmRA=-3.0mas/yr, pmDE=1.9mas/yr; 149 = [BC02] 11; known X-ray source; log(Lx(ROSAT/PSPC))=31.01erg/s; pmRA=0.6mas/yr, pmDE=-12.6mas/yr; 161 = [MJD95] 653; pmRA=-1.0mas/yr, pmDE=-5.4mas/yr Note (2): The errors of the BRI magnitudes are <0.02mag in general for stars V<17mag and become >0.05mag for fainter stars V>19mag (Berghofer & Christian 2002, Cat. J/A+A/384/890). The mean photometric uncertainties in FLAMINGOS are 0.058±0.012, 0.064±0.018, and 0.056±0.014 for J, H, and K, respectively Roman-Zuniga et al. (2008ApJ...672..861R). The typical errors are much smaller for brighter stars (e.g., σJ=0.02mag for stars with J<16mag). For 2MASS photometric quality flags, see Cutri et al. (2003, Cat. II/246).
Global notes: Note (G1): * The X-ray sources are <[WFT2010] NNN> = <CXOU JHHMMSS.s+DDMMSS> (truncated) in Simbad. * In table 4, FLAMINGOS sources are <[WFT2010] FLAMINGOS JHHMMSS+DDMMSS> in Simbad.
History: From electronic version of the journal References: Wang et al. Paper I. 2008ApJ...675..464W Cat. J/ApJ/675/464 Wang et al. Paper II. 2009ApJ...696...47W Cat. J/ApJ/696/47
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 30-May-2012
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