J/ApJ/696/1278 The extended star-forming environment of M17 (Povich+, 2009)
The extended environment of M17: a star formation history.
Povich M.S., Churchwell E., Bieging J.H., Kang M., Whitney B.A.,
Brogan C.L., Kulesa C.A., Cohen M., Babler B.L., Indebetouw R., Meade M.R.,
Robitaille T.P.
<Astrophys. J., 696, 1278-1306 (2009)>
=2009ApJ...696.1278P 2009ApJ...696.1278P
ADC_Keywords: H II regions ; Photometry, infrared ; Spectral types ; Stars, OB ;
YSOs ; X-ray sources
Keywords: H II regions - infrared: ISM - radio continuum: ISM -
radio lines: ISM - stars: formation
Abstract:
M17 is one of the youngest and most massive nearby star-formation
regions in the Galaxy. It features a bright HII region erupting as a
blister from the side of a giant molecular cloud (GMC). Combining
photometry from the Spitzer Galactic Legacy Infrared Mid-Plane Survey
Extraordinaire (GLIMPSE) with complementary infrared (IR) surveys, we
identify candidate young stellar objects (YSOs) throughout a
1.5x1° field that includes the M17 complex. The long sightline
through the Galaxy behind M17 creates significant contamination in our
YSO sample from unassociated sources with similar IR colors. Removing
contaminants, we produce a highly reliable catalog of 96 candidate
YSOs with a high probability of association with the M17 complex. We
fit model spectral energy distributions to these sources and constrain
their physical properties. Extrapolating the mass function of 62
intermediate-mass YSOs (M*>3M☉), we estimate that >1000 stars
are in the process of forming in the extended outer regions of M17.
The remaining 34 candidate YSOs are found in a 0.17deg2 field
containing the well-studied M17 HII region and photodissociation
region (PDR), where bright diffuse mid-IR emission drastically reduces
the sensitivity of the GLIMPSE point-source detections.
Description:
As part of the Spitzer Legacy Science Program, GLIMPSE (Benjamin et
al. 2003PASP..115..953B 2003PASP..115..953B) imaged the Galactic plane from |l|=0-65°,
|b|≤1° using the four mid-IR bands (3.6, 4.5, 5.8, and 8.0um) of
the Infrared Array Camera (IRAC) on the Spitzer Space Telescope.
For this study, we use the GLIMPSE v2.0 Point Source Archive and
the GLIMPSE v3.0 image mosaics.
We downloaded 24um and 70um post-BCD mosaics of the MIPSGAL survey
(Carey et al. 2009PASP..121...76C 2009PASP..121...76C) from the Spitzer Science Center.
After selecting YSO candidates based on the combined GLIMPSE and MIPS
[24] photometry, we correlated only the brightest saturated and
near-saturated YSO candidates with the MSX catalog, using a 6"
correlation radius.
We mapped the M17 region in the J=2->1 transitions of 12CO and
13CO with the 10m Heinrich Hertz Telescope (HHT) on Mt. Graham,
Arizona between 2008 February and 2008 June.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 66 62 Candidate YSOs in the extended environment of M17
table3.dat 48 135 Other candidate clustered YSOs in the M17 target
field
table4.dat 53 34 Candidate YSOs in the region observed by Chandra
table5.dat 96 25 Selected OB stars associated with M17
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See also:
II/293 : GLIMPSE Source Catalog (I + II + 3D) (IPAC 2008)
V/114 : MSX6C Infrared Point Source Catalog (Egan+ 2003)
V/112 : Catalog of Star-Forming Regions in the Galaxy (Avedisova, 2002)
J/ApJ/658/1264 : IR-excess sources in GLIMPSE and MSX (Uzpen+, 2007)
J/ApJS/169/353 : Chandra sources in M17 (Broos+, 2007)
J/A+A/392/971 : Catalogue of bright YSO candidates in ISOGAL (Felli+, 2002)
http://www.astro.wisc.edu/glimpse/docs.html : GLIMPSE documents online
http://irsa.ipac.caltech.edu/applications/Gator : Spitzer and MSX public
databases online
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Field M17 field (1)
8- 10 A3 --- [PCB2009] Star designation (ENN)
12 A1 --- f_[PCB2009] [bc] Flag on [PCB2009] (2)
14- 20 F7.4 deg GLON Galactic longitude in decimal degrees (J2000)
22- 28 F7.4 deg GLAT Galactic latitude in decimal degrees (J2000)
30- 33 F4.1 mag 4.5mag Spitzer/IRAC 4.5um band magnitude
35 A1 --- l_8mag Limit flag on 8mag
36- 39 F4.1 mag 8mag ? Spitzer/IRAC 8.0um band magnitude
41 A1 --- l_24mag Limit flag on 24mag
42- 45 F4.1 mag 24mag ? Spitzer/IRAC 24um band magnitude
47- 49 F3.1 Msun M*min Minimum stellar mass
51- 52 I2 Msun M*max Maximum stellar mass
54- 57 F4.1 [Lsun] logLmin Minimum Ltot (total bolometric luminosity,
including luminosity produced by accretion)
59- 61 F3.1 [Lsun] logLmax Ltot maximum
63- 66 A4 --- Stage Evolutionary stage (3)
-------------------------------------------------------------------------------
Note (1): The sources presented in this table are found within the white
boundary lines but outside the rectangle in Figure 10. While the
association of any given source with M17 is uncertain, the groupings
of candidate YSOs are significant.
* the "Bridge" is a molecular gas structure connecting the M17
molecular cloud with the giant molecumar cloud (GMC) complex
extending 85pc to the southwest.
* "Outer" is for the outer regions of the M17 GMC. Although our
cluster-finding algorithm selects 2 candidate YSOs apparently
located in MC15.9-0.7, these sources are likely unassociated.
* "M17 EB" is the M17 extended bubble
* "MC" is the M17 molecular cloud G15.9-0.7
See figure 1 for further details of M17 fields.
Note (2): Flag as follows:
b = Source E25 is resolved by IRAC and is also an MSX point source.
Its SED exhibits PAH emission.
c = Source E55 is the candidate protostar shown in Figure 12.
Note (3): "Amb." means that the well-fit models are divided between
different evolutionary stages
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- [PCB2009] Index number (FNNN) (1)
5 A1 --- f_[PCB2009] [b] Flag on [PCB2009] (2)
7- 13 F7.4 deg GLON Galactic longitude in decimal degrees (J2000)
15- 21 F7.4 deg GLAT Galactic latitude in decimal degrees (J2000)
23 A1 --- l_4.5mag Limit flag on 4.5mag
24- 27 F4.1 mag 4.5mag ? Spitzer/IRAC 4.5um magnitude
29 A1 --- l_8mag Limit flag on 8mag
30- 33 F4.1 mag 8mag ? Spitzer/IRAC 8.0um magnitude
35 A1 --- l_24mag Limit flag on 24mag
36- 39 F4.1 mag 24mag Spitzer/IRAC 24um magnitude
41- 48 A8 --- Group M17 group (3)
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Note (1): The sources presented in this table are found outside the white
boundary lines in Figure 10. The majority of these sources are at
unknown distances.
Note (2):
b = These four sources are resolved by IRAC. F53, F87, and F89 are detected
by MSX and may be compact HII regions ionized by young clusters rather
than single YSOs.
Note (3): Groups of these candidate YSOs are apparently associated with
prominent molecular cloud structures as follows:
SW = the near end of the large GMC complex at v=20km/s extending
southwest from M17;
MC G14.9 = the molecular cloud G14.9-0.4 at v=60km/s (see Figure 1);
Bu G15.7 = an IR/CO shell structure, 4' in diameter, centered at
(l, b)=(15.67°,-0.29°) and v∼45km/s.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- [PCB2009] Index number (XNN or NXNN) (1)
6 A1 --- f_[PCB2009] [b-f] Flag on [PCB2009] (2)
8- 14 F7.4 deg GLON Galactic longitude in decimal degrees (J2000)
16- 22 F7.4 deg GLAT Galactic latitude in decimal degrees (J2000)
24 A1 --- l_4.5mag Limit flag on 4.5mag
25- 28 F4.1 mag 4.5mag ? Spitzer/IRAC 4.5um magnitude
30- 33 F4.1 mag 8mag ? Spitzer/IRAC 8.0um magnitude
35- 37 F3.1 Msun M*min Minimum stellar mass
39- 40 I2 Msun M*max Maximum stellar mass
42- 44 F3.1 [Lsun] logLmin Minimum Ltot (total bolometric luminosity,
including luminosity produced by accretion)
46- 48 F3.1 [Lsun] logLmax Ltot maximum
50- 53 A4 --- Stage Evolutionary stage (3)
-------------------------------------------------------------------------------
Note (1): X for sources with X-ray counterparts or NX.
See figure 10 for field observed to date by Chandra in M17.
Note (2): Flag as follows:
b = Selected as X-ray emitting candidate "protostars" in Table 7 of
Broos et al. 2007, Cat. J/ApJS/169/353.
c = X4 is the KW Object (see Figure 13).
d = These six sources are located away from the bright 8um emission of the
M17 PDR, increasing the odds that they are unassociated contaminants.
e = NX5 is resolved by IRAC (see Figure 13).
f = NX10 is located at the tip a prominent pillar structure in the M17 HII
region. Jiang et al. (2002ApJ...577..245J 2002ApJ...577..245J) resolve this source into two
YSOs of comparable brightness in the near-IR, a Class I and a Class
II/III candidate. The Class I source likely dominates the mid-IR
emission.
Note (3): "Amb." means that the well-fit models are divided between
different evolutionary stages
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- OType Object type (1)
5- 7 A3 --- [PCB2009] Index number (2)
9 A1 --- f_[PCB2009] [dfgh] Flag on [PCB2009] (3)
11- 25 A15 --- OName Alternative name (4)
27- 33 F7.4 deg GLON Galactic longitude in decimal degrees (J2000)
35- 41 F7.4 deg GLAT Galactic latitude in decimal degrees (J2000)
43- 50 A8 --- SpTcat Cataloged MK spectral type (5)
52- 67 A16 --- SpT1.6 MK spectral type from SED with d=1.6kpc
69- 89 A21 --- SpT2.1 MK spectral type from SED with d=2.1kpc
90 A1 --- f_SpT2.1 [e] Flag on SpT2.1 (6)
92 A1 --- u_Av [~] Approximative symbol for Av
93- 96 F4.1 mag Av ? Extinction value
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Note (1): Stars as follows:
O* = O stars in NGC 6618. All O stars in NGC 6618 are Chandra point sources
(Broos et al. 2007, Cat. J/ApJS/169/353).
OB* = Candidate OB stars in NGC 6618PG. The only star in NGC 6618PG that has
been observed by Chandra, No. 20, is also an X-ray point source.
OBa = Candidate OB stars associated with 24um emission in M17 EB
Note (2): OB stars in each of the first two groups are listed in order of
decreasing luminosity, while the candidate B stars in the final group
are listed in order of increasing Galactic longitude.
Note (3): Flag as follows:
d = CEN 1a,b refer to the main components of an apparent O4+O4 visual
binary that are saturated and marginally resolved by IRAC. CEN 1a,b
each are spectroscopic binary systems with nearly equal-luminosity
components (Hoffmeister et al. 2008ApJ...686..310H 2008ApJ...686..310H).
f = BD-16 4826 is a ROSAT point source (Dunne et al. 2003ApJ...590..306D 2003ApJ...590..306D).
g = This source, ISOGAL-P J182108.8-155658 from the catalog of Felli et al.
(2002, Cat J/A+A/392/971), exhibits a marginal IR excess at 5.8um and
is not detected as a point source at 8.0um.
h = This source exhibits an IR excess at 8um.
Note (4): "CEN NNN" = Chini et al. (1980A&A....91..186C 1980A&A....91..186C; <Cl* NGC 6618 CEN NNN>
in Simbad), and "OI NNN" = Ogura & Ishida (1976PASJ...28...35O 1976PASJ...28...35O;
in Simbad).
SWB M17-3 is a recently discovered O star driving a stellar wind bow
shock (Povich et al. 2008ApJ...689..242P 2008ApJ...689..242P).
Other identifiers are from SIMBAD.
Note (5): Spectral types for NGC 6618 are from Ogura & Ishida,
1976PASJ...28...35O 1976PASJ...28...35O, Chini et al., 1980A&A....91..186C 1980A&A....91..186C, Hanson et al.,
1997ApJ...489..698H 1997ApJ...489..698H, and Hoffmeister et al., 2008ApJ...686..310H 2008ApJ...686..310H;
others are from SIMBAD.
Note (6): At 2.1kpc, the SED fits to OI 352 return a radius larger than that
of an O supergiant. It may be an unresolved multiple O system (see text).
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 10-May-2011