J/ApJ/688/1142 Star formation in W5: Spitzer observations (Koenig+, 2008)
Clustered and triggered star formation in W5: observations with Spitzer.
Koenig X.P., Allen L.E., Gutermuth R.A., Hora J.L., Brunt C.M.,
Muzerolle J.
<Astrophys. J., 688, 1142-1158 (2008)>
=2008ApJ...688.1142K 2008ApJ...688.1142K
ADC_Keywords: H II regions ; Photometry, infrared ; Stars, pre-main sequence ;
Active gal. nuclei
Keywords: H II regions - infrared: stars - ISM: globules - stars: early-type -
stars: formation - stars: pre-main sequence
Abstract:
We present images and initial results from our extensive Spitzer Space
Telescope imaging survey of the W5 HII region with the Infrared Array
Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS). We
detect dense clusters of stars, centered on the O stars HD 18326,
BD +60 586, HD 17505, and HD 17520. At 24um, substantial extended
emission is visible, presumably from heated dust grains that survive
in the strongly ionizing environment of the HII region. With
photometry of more than 18000 point sources, we analyze the clustering
properties of objects classified as young stars by their IR spectral
energy distributions (a total of 2064 sources) across the region using
a minimal-spanning-tree algorithm. We find ∼40%-70% of infrared excess
sources belong to clusters with ≥10 members. We find that within the
evacuated cavities of the HII regions that make up W5, the ratio of
Class II to Class I sources is ∼7 times higher than for objects
coincident with molecular gas as traced by 12CO emission and near-IR
extinction maps. We attribute this contrast to an age difference
between the two locations and postulate that at least two distinct
generations of star formation are visible across W5. Our preliminary
analysis shows that triggering is a plausible mechanism to explain the
multiple generations of star formation in W5 and merits further
investigation.
Description:
W5 was observed with the Spitzer IRAC instrument in all four bands
(3.6, 4.5, 5.8, and 8.0um). The observations were broken down into
three rectangular Astronomical Observing Requests (AORs) covering
∼1.8x1.6°, in 2006 Sep 20,28 and 2007 Feb 16.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 120 17771 W5 source list
table4.dat 32 18 Star-forming globules in W5
table6.dat 121 927 W5 extragalactic sources
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See also:
J/A+A/503/107 : Spitzer/IRAC view of Sh2-284 (Puga+, 2009)
J/ApJ/674/336 : Spitzer observations of NGC 1333 (Gutermuth+, 2008)
J/ApJ/678/200 : YSOs in N63 and N180 (Caulet+, 2008)
J/ApJ/643/965 : Spitzer photometry of the Trifid nebula (M20) (Rho+, 2006)
J/ApJ/639/1069 : Radial velocities in the Cas OB6 association (Hillwig+, 2006)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- ID Source identification (<[KAG2008] NNNNN> in
Simbad)
7- 15 F9.6 deg RAdeg Right Ascension in decimal degrees (J2000)
17- 25 F9.6 deg DEdeg Declination in decimal degrees (J2000)
27- 31 F5.2 mag Jmag ? 2MASS J band magnitude
33- 36 F4.2 mag e_Jmag ? Error in Jmag
38- 42 F5.2 mag Hmag ? 2MASS H band magnitude
44- 47 F4.2 mag e_Hmag ? Error in Hmag
49- 53 F5.2 mag Ksmag ? 2MASS Ks band magnitude
55- 58 F4.2 mag e_Ksmag ? Error in Kmag
60- 64 F5.2 mag [3.6] Spitzer/IRAC 3.6 micron band magnitude
66- 69 F4.2 mag e_[3.6] Error in [3.6]
71- 75 F5.2 mag [4.5] Spitzer/IRAC 4.5 micron band magnitude
77- 80 F4.2 mag e_[4.5] Error in [4.5]
82- 86 F5.2 mag [5.8] ? Spitzer/IRAC 5.8 micron band magnitude
88- 91 F4.2 mag e_[5.8] ? Error in [5.8]
93- 97 F5.2 mag [8.0] ? Spitzer/IRAC 8.0 micron band magnitude
99-102 F4.2 mag e_[8.0] ? Error in [8.0]
104-108 F5.2 mag [24] ? Spitzer/MIPS 24 micron band magnitude
110-113 F4.2 mag e_[24] ? Error in [24]
115-118 A4 --- Type Source type as defined in text (1)
120 A1 --- f_Type [v?-] Source flag (2)
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Note (1): Source type as follows:
Deep = "deeply embedded protostars": Class I sources with bright emission
at 24um and very red IRAC-24um color ([X]-[24]>4.5, where X is the
magnitude in any of the four IRAC bands).
I = protostars
II = stars with disks
III = stars exhibiting only photospheric colors
TD = transition disk candidates
See section 3.1 for further details.
Note (2): Flags as follows:
v = unusual SED shape;
? = uncertain source class.
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- ID Source identification (<[KAG2008] globule NN>
in Simbad)
4 I1 h RAh Hour of right ascension (J2000)
6- 7 I2 min RAm Minute of right ascension (J2000)
9- 13 F5.2 s RAs Second of right ascension (J2000)
15 A1 --- DE- Declination sign (J2000)
16- 17 I2 deg DEd Degree of declination (J2000)
19- 20 I2 arcmin DEm Arcminute of declination (J2000)
22- 26 F5.2 arcsec DEs Arcsecond of declination (J2000)
28- 32 A5 --- Type Comet (for cometary) or Trunk (1)
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Note (1): trunk designed small "elephant trunk" formations within the HII region
cavity which contain Class I or Class II objects. See section 4.3 for
further details.
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Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- ID Source identification (<[KAG2008] gNNN> in
Simbad)
6- 14 F9.6 deg RAdeg Right Ascension in decimal degrees (J2000)
16- 24 F9.6 deg DEdeg Declination in decimal degrees (J2000)
26- 30 F5.2 mag Jmag ? 2MASS J band magnitude
32- 35 F4.2 mag e_Jmag ? Error in Jmag
37- 41 F5.2 mag Hmag ? 2MASS H band magnitude
43- 46 F4.2 mag e_Hmag ? Error in Hmag
48- 52 F5.2 mag Ksmag ? 2MASS Ks band magnitude
54- 57 F4.2 mag e_Ksmag ? Error in Kmag
59- 63 F5.2 mag [3.6] Spitzer/IRAC 3.6 micron band magnitude
65- 68 F4.2 mag e_[3.6] Error in [3.6]
70- 74 F5.2 mag [4.5] Spitzer/IRAC 4.5 micron band magnitude
76- 79 F4.2 mag e_[4.5] Error in [4.5]
81- 85 F5.2 mag [5.8] Spitzer/IRAC 5.8 micron band magnitude
87- 90 F4.2 mag e_[5.8] Error in [5.8]
92- 96 F5.2 mag [8.0] Spitzer/IRAC 8.0 micron band magnitude
98-101 F4.2 mag e_[8.0] Error in [8.0]
103-107 F5.2 mag [24] ? Spitzer/MIPS 24 micron band magnitude
109-112 F4.2 mag e_[24] ? Error in [24]
114-116 A3 --- Type Galaxy type (1)
118-121 F4.2 --- Prob Probability that the object is a YSO (2)
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Note (1): AGN (729 objects) or "PAH galaxy" (198 objects).
Note (2): Probability that an object in our AGN list of given d6 (nearest
neighbor distance), [4.5] and [4.5]-[8.0] color is a YSO.
See appendix for further details.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 18-Jan-2011