J/ApJS/69/99 NGC 6334 centers of star formation JHK photometry (Straw+ 1989)
The centers of star formation in NGC 6334 and their stellar mass distributions
Straw S.M., Hyland A.R., McGregor P.J.
<Astrophys. J. Suppl. Ser. 69, 99 (1989)>
=1989ApJS...69...99S 1989ApJS...69...99S (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Supernova remnants ; Photometry, infrared
Keywords: clusters: open - interstellar: molecules - luminosity function -
nebulae: H II regions - nebulae: individual (NGC 6334) -
stars: formation
Abstract:
We present near-infrared observations of specific sites of high-mass
star formation activity in the giant H II region/molecular cloud
complex NGC 6334. The observations consist of high-spatial resolution
broad-band imaging, chopping photometry, and moderate-resolution
spectra. The imaging observations provide full spatial sampling of the
stellar population over a significant area of the cloud to a limit of
K=13.5mag and reveal many faint red sources around the sites of recent
high-mass star formation. We show that most of these sources are
associated with the NGC 6334 molecular cloud and are not Galactic
field sources. In the majority of the regions the embedded sources are
primarily reddened main-sequence stars of low and intermediate mass
though in three of the 11 regions studied there is a high proportion
of objects showing H-K excesses which are therefore probably pre
main-sequence. We identify the red objects in FIR-I as belonging to a
very young compact cluster of ∼1pc spatial extent. In FIR-V an
unexpectedly large number of bright red sources are detected which
have CO absorption at 2.3µm. The probability that these objects are
Galactic field sources is very low and if they are giant stars
associated with NGC 6334 their implied ages (>109yr) are
inconsistent with the many indicators of extreme youth in this region.
We propose that they form a hitherto unrecognized population of
high-luminosity pre-main-sequence objects. Two objects with similar
characteristics are also found in images of an area of the NGC 6334
molecular cloud to the north of FIR-V (SH-1). In FIR-V we also find
evidence that the molecular outflow from the already known high-mass
protostar has triggered intermediate-mass star formation via
interaction with the local interstellar medium. Mass functions have
been derived for the embedded stellar aggregates under the assumption
that all sources lie on the main sequence unless otherwise indicated.
The effect of a population of pre-main-sequence objects on the derived
mass function slopes is shown to be small. Embedded aggregates in NGC
6334 have stellar mass distributions similar to those found both in
young visible clusters and in other embedded clusters. This suggests
that the slope of the mass function is relatively insensitive to
conditions in the star formation environment and that the solar
neighborhood value applies to star formation regions on scales as
small as 1pc and of ages less than 107yr.
Objects:
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RA (2000) DE Designation(s)
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17 19 57.9 -35 57 47 NGC 6334
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2 92 464 Infrared sources in NGC 6334
table3 38 164 Photometry and positions from supplementary imaging
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Byte-by-byte Description of file: table2
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Bytes Format Units Label Explanations
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1- 17 A17 --- IRS IRS name
18 A1 --- n_IRS [*] Note on photometric results (1)
20- 21 I2 h RAh Right ascension (1950)
23- 24 I2 min RAm Right ascension (1950)
26- 29 F4.1 s RAs Right ascension (1950)
31 A1 --- DE- Declination sign
32- 33 I2 deg DEd Declinaiton (1950)
35- 36 I2 arcmin DEm Declinaiton (1950)
38- 39 I2 arcsec DEs Declinaiton (1950)
41- 45 F5.2 mag Kmag K magnitude
47 A1 --- l_J-H Limit flag on J-H
48- 52 F5.2 mag J-H ? J-H colour index
54 A1 --- l_H-K Limit flag on H-K
55- 59 F5.2 mag H-K ? H-K colour index
61 A1 --- l_J-K Limit flag on J-K
62- 66 F5.2 mag J-K ? J-K colour index
68- 72 F5.2 mag K0 ? Derreddened K magnitude (2)
74- 77 F4.2 [solMass] LogM ? Stellar mass (2)
78 A1 --- n_LogM [*#] Note on Mass (3)
80- 94 A15 --- Rem Remarks (4)
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Note (1): Asterisks indicate chopping photometry results; all other photometry
is derived from the images.
Note (2): The derivation of dereddened K magnitudes and stellar masses are
described in chap IIIb of the paper.
Note (3): *: Masses taken from Harvey and Gatley 1983ApJ...269..613H 1983ApJ...269..613H
#: Masses derived from dereddening to pre-main-sequence tracks
(Fig. 10) instead of ZAMS.
Note (4): Edge: Source not covered by the J and/or H imaging area
Opt: Source visible in the SRC-I plate
Fore: Likely foreground source based on its near-infrared colors
Ext: Extended source at K
Neb: Probable knot in diffuse emission
Back: Galactic background source (based on CVF data and/or reddening
information)
CVF: Spectrum obtained (Fig. 3).
Abbreviations for previously reported photometry
HG: Harvey and Gatley 1983ApJ...269..613H 1983ApJ...269..613H
PF: Persi and Ferrari-Toniolo 1982A&A...112..292P 1982A&A...112..292P
BN: Becklin and Neugebauer 1974, Proc. of the Eighth ESLAB Symp.
HII regions and the Galactic center, ed. A.F.M. Moorwood
(Neuilly: ESRO), p. 39.
BE: Braz and Epchtein 1982A&A...111...91B 1982A&A...111...91B
HW: Harvey and Wilding 1984ApJ...280L..19H 1984ApJ...280L..19H
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Byte-by-byte Description of file: table3
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Bytes Format Units Label Explanations
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1- 10 A10 --- IRS IRS name
12- 13 I2 h RAh Right ascension (1950)
15- 16 I2 min RAm Right ascension (1950)
18- 21 F4.1 s RAs Right ascension (1950)
23 A1 --- DE- Declination sign
24- 25 I2 deg DEd Declinaiton (1950)
27- 28 I2 arcmin DEm Declinaiton (1950)
30- 31 I2 arcsec DEs Declinaiton (1950)
33- 37 F5.2 mag Kmag K magnitude
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History: Prepared via OCR at CDS.
(End) Marie-Jose Wagner, Patricia Bauer [CDS] 02-May-1997