2004ApJ...616.1042O


Query : 2004ApJ...616.1042O

2004ApJ...616.1042O - Astrophys. J., 616, 1042-1057 (2004/December-1)

A near-infrared study of the NGC 7538 star-forming region.

OJHA D.K., TAMURA M., NAKAJIMA Y., FUKAGAWA M., SUGITANI K., NAGASHIMA C., NAGAYAMA T., NAGATA T., SATO S., VIG S., GHOSH S.K., PICKLES A.J., MOMOSE M. and OGURA K.

Abstract (from CDS):

We present subarcsecond (FWHM∼0".7), near-infrared (NIR) JHK_s_-band images and a high-sensitivity radio continuum image at 1280 MHz, using SIRIUS on the University of Hawaii 88 inch (2.2 m) telescope and the Giant Metrewave Radio Telescope (GMRT). The NIR survey covers an area of ∼24 arcmin2 with 10 σ limiting magnitudes of ∼19.5, 18.4, and 17.3 in the J, H, and Ksbands, respectively. Our NIR images are deeper than any JHK surveys to date for the larger area of the NGC 7538 star-forming region. We construct JHK color-color and J-H/J and H-K/K color-magnitude diagrams to identify young stellar objects (YSOs) and to estimate their masses. Based on these color-color and color-magnitude diagrams, we identified a rich population of YSOs (Class I and Class II) associated with the NGC 7538 region. A large number of red sources (H-K>2) have also been detected around NGC 7538. We argue that these red stars are most probably pre-main-sequence stars with intrinsic color excesses. Most of the YSOs in NGC 7538 are arranged from the northwest toward the southeast regions, forming a sequence in age: a diffuse H II region (northwest and oldest, where most of the Class II and Class I sources are detected), a compact IR core (center), and regions with an extensive IR reflection nebula and a cluster of red young stars (southeast and south). We find that the slope of the Ks-band luminosity function of NGC 7538 is lower than the typical values reported for young embedded clusters, although equally low values have also been reported in the W3 Main star-forming region. From the slope of the Ks-band luminosity function and the analysis by Megeath and coworkers, we infer that the embedded stellar population is composed of YSOs with an age of ∼1 Myr. Based on the comparison of models of pre-main-sequence stars with the observed color-magnitude diagram, we find that the stellar population in NGC 7538 is primarily composed of low-mass pre-main-sequence stars similar to those observed in the W3 Main star-forming region. The radio continuum image from the GMRT observations at 1280 MHz shows an arc-shaped structure due to the interaction between the H II region and the adjacent molecular cloud. The ionization front at the interface between the H II region and the molecular cloud is clearly delineated by comparing the radio continuum, molecular line, and NIR images.

Abstract Copyright:

Journal keyword(s): Infrared: Stars - ISM: Clouds - ISM: Individual: NGC Number: NGC 7538 - Galaxy: Open Clusters and Associations: General - Stars: Formation - Stars: Pre-Main-Sequence

Nomenclature: Table 1: [OTN2004b] IRS 9AN (Nos 9N1 to 9N4). Text: [OTN2004b] JHHMMSS.ss+DDMMSS.s N=2.

CDS comments: Table 1: Sources IRS N and IRS Na are [WBN72] W 3 IRS N and [WBN72] W 3 IRS Na in SIMBAD.

Simbad objects: 22

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Number of rows : 22
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 [WBN74] NGC 7538 IRS 8 IR 23 13 27.3 +61 30 49           ~ 18 0
2 2MASS J23133024+6130103 Y*? 23 13 30.2430274824 +61 30 10.334305152           O9.5V+B0.5V 26 0
3 [WBN74] NGC 7538 IRS 4 HII 23 13 32.7 +61 29 04           ~ 22 1
4 TYC 4279-1463-1 * 23 13 34.3977427416 +61 30 14.637855024   12.76 11.66     O3.5V((f*))+O9.5V 24 0
5 TYC 4279-1349-1 * 23 13 36.8131356912 +61 30 39.613105188   14.43 11.57     K 20 2
6 NGC 7538 OpC 23 13 37 +61 30.0           ~ 853 1
7 [WBN74] NGC 7538 IRS 3 Y*? 23 13 43.646 +61 28 14.02           ~ 65 0
8 2MASS J23134377+6126439 Y*? 23 13 43.77 +61 26 44.0           ~ 2 0
9 [WBN74] NGC 7538 IRS 11 Y*O 23 13 43.901 +61 26 57.98           ~ 56 0
10 [OTN2004b] J231344.65+612647.9 IR 23 13 44.65 +61 26 47.9           ~ 1 0
11 NGC 7538S Y*O 23 13 44.8 +61 26 51           ~ 84 1
12 [WBN74] NGC 7538 IRS 1 Y*O 23 13 45.318 +61 28 11.69           ~ 398 3
13 NGC 7538B HII 23 13 45.35 +61 28 10.3           ~ 13 0
14 [WBN74] NGC 7538 IRS 2 Y*? 23 13 45.4691116296 +61 28 19.985984832           ~ 73 0
15 SH 2-158 A HII 23 13 45.580 +61 28 18.02           ~ 12 0
16 [OTN2004b] IRS 9N1 IR 23 14 01.36 +61 27 18.4           ~ 2 0
17 IRAS 23118+6110 Y*O 23 14 01.63 +61 27 20.2           ~ 363 0
18 [OTN2004b] IRS 9N4 IR 23 14 02.40 +61 27 20.4           ~ 2 0
19 [OTN2004b] IRS 9N3 IR 23 14 02.56 +61 27 24.6           ~ 2 0
20 [OTN2004b] IRS 9N2 IR 23 14 02.70 +61 27 14.1           ~ 2 0
21 [WBN74] NGC 7538 IRS 10 Em* 23 14 06.5907341040 +61 27 57.771865800           ~ 15 0
22 Ass Cas OB 2 As* 23 20 +60.9           ~ 66 0

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2022.10.07-15:08:39

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