J/ApJ/839/108 YSOs in the star-forming regions W51 & W43 (Saral+, 2017)
Young stellar objects in the massive star-forming regions W51 and W43.
Saral G., Hora J.L., Audard M., Koenig X.P., Martinez-Galarza J.R.,
Motte F., Nguyen-Luong Q., Saygac A.T., Smith H.A.
<Astrophys. J., 839, 108 (2017)>
=2017ApJ...839..108S 2017ApJ...839..108S
ADC_Keywords: Photometry, infrared ; YSOs ; Stars, masses
Keywords: infrared: stars ; stars: early-type ; stars: formation ;
stars: pre-main sequence
Abstract:
We present the results of our investigation of the star-forming
complexes W51 and W43, two of the brightest in the first Galactic
quadrant. In order to determine the young stellar object (YSO)
populations in W51 and W43 we used color-magnitude relations based on
Spitzer mid-infrared and 2MASS/UKIDSS near- infrared data. We
identified 302 Class I YSOs and 1178 Class II/transition disk
candidates in W51, and 917 Class I YSOs and 5187 Class II/transition
disk candidates in W43. We also identified tens of groups of YSOs in
both regions using the Minimal Spanning Tree (MST) method. We found
similar cluster densities in both regions, even though Spitzer was not
able to probe the densest part of W43. By using the Class II/I ratios,
we traced the relative ages within the regions and, based on the
morphology of the clusters, we argue that several sites of star
formation are independent of one another in terms of their ages and
physical conditions. We used spectral energy distribution- fitting to
identify the massive YSO (MYSO) candidates since they play a vital
role in the star formation process, and then examined them to see if
they are related to any massive star formation tracers such as UCH II
regions, masers, or dense fragments. We identified 17 MYSO candidates
in W51, and 14 in W43, respectively, and found that groups of YSOs
hosting MYSO candidates are positionally associated with H II regions
in W51, though we do not see any MYSO candidates associated with
previously identified massive dense fragments in W43.
Description:
We used the mid-infrared Spitzer data from several programs obtained
with the Spitzer IRAC instrument at 3.6, 4.5, 5.8, and 8.0um.
For W51, we used the 2s frame time data taken at all wavelengths in
2007 and prior years are from the GLIMPSE Legacy Survey (Churchwell+
2009PASP..121..213C 2009PASP..121..213C, program ID 187). The data obtained in 2012 and
afterward were performed during the warm mission, so only 3.6 and
4.5um data were obtained. We also used 30s frame time data from other
programs taken in October 2004, 2005, and June 2013, with the
following program IDs: 2313 (PI: M. Kuchner), 20026 (PI: T. von
Hippel), and 90095 (PI: K. Luhman). We also obtained 30s data in High
Dynamic Range (HDR) mode in December 2014 (project ID: 10012, PI: J.
Hora), which performs consecutive individual observations with frame
times of 1.2s and 30s.
The IRAC data for the W43 region are from the GLIMPSE Legacy Survey
(Benjamin+ 2003PASP..115..953B 2003PASP..115..953B ; Churchwell+ 2009PASP..121..213C 2009PASP..121..213C,
program IDs 186, 30570) and 30s HDR data were taken with program IDs
10012 and 80058 (PI: J. Hora); observations span 2004 Apr to 2014 Nov.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table6.dat 74 25 Properties of the clusters in W51
table7.dat 74 146 Properties of the clusters in W43
table10.dat 86 17 Physical parameters of massive YSO candidates in W51
table11.dat 86 14 Physical parameters of massive YSO candidates in W43
w43cat.dat 194 641732 W43 Spitzer 2MASS/UKIDSS final catalog
w51cat.dat 194 285252 W51 Spitzer 2MASS/UKIDSS final catalog
--------------------------------------------------------------------------------
Description of file: W43FinalCatalog.fits and W51FinalCatalog.fits,
the original catalogs in FITS format, are available on the FTP.
See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/316 : UKIDSS-DR6 Galactic Plane Survey (Lucas+ 2012)
VIII/64 : Westerhout's Catalog of Discrete Sources (Westerhout, 1958)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/A+A/371/497 : OB associations in spiral gal. NGC 300 (Pietrzynski+, 2001)
J/A+A/440/121 : K magnitudes of OB stars in UCHIIs (Bik+, 2005)
J/A+A/476/1243 : Millimeter continuum mapping of Cygnus X (Motte+, 2007)
J/ApJ/669/327 : S3MC: YSOs in N66, in SMC (Simon+, 2007)
J/ApJ/674/336 : Spitzer observations of NGC 1333 (Gutermuth+, 2008)
J/ApJ/688/1142 : Star formation in W5: Spitzer observations (Koenig+, 2008)
J/ApJS/181/321 : Properties of Spitzer c2d dark clouds (Evans+, 2009)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/ApJ/706/83 : Embedded YSO candidates in W51 (Kang+, 2009)
J/ApJ/720/679 : Optical spectroscopy in Cygnus X region (Beerer+, 2010)
J/ApJ/720/1055 : VBLA observations of W51 Main/South (Sato+, 2010)
J/ApJ/727/64 : Young stellar groups & their most massive stars (Kirk+, 2011)
J/A+A/525/A149 : Red MSX Survey (RMS): bol. fluxes of YSOs (Mottram+, 2011)
J/ApJ/752/127 : IR observations of AFGL 490 (Masiunas+, 2012)
J/A+A/560/A24 : IRAM 30m CO-observations in W43 (Carlhoff+, 2013)
J/AJ/148/11 : Infrared photometry in Cygnus-X (Kryukova+, 2014)
J/AJ/150/95 : Masses and ages of YSOs in Per OB2 (Azimlu+, 2015)
J/AJ/149/64 : MIPSGAL 24µm point source catalog (Gutermuth+, 2015)
J/ApJ/813/25 : YSO candidates in W49 observed with Spitzer (Saral+, 2015)
J/ApJ/827/96 : WISE census of YSOs in Canis Major (Fischer+, 2016)
Byte-by-byte Description of file: table[67].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Group [1/95] Group running number
3- 3 A1 --- m_Group [a-g*] SubGroup letter code (1)
5- 14 F10.6 deg RAdeg Right ascension in decimal degrees (J2000) (2)
16- 24 F9.6 deg DEdeg Declination in decimal degrees (J2000) (2)
26- 29 I4 --- Nir [10/3047] Number of IR excess sources in
group/subgroup (3)
31- 33 I3 --- NI [0/561] Number of Class I candidates
35- 38 I4 --- NII [4/2358] Number of Class II candidates
40- 44 F5.2 --- II/I [0.5/21]? Class II to Class I ratio
46- 50 F5.2 --- e_II/I [0.2/29]? Uncertainty in II/I
52- 53 I2 --- Np [0/73] Number of deeply embedded protostar
candidates
55- 56 I2 --- Nt [0/55] Number of transition disk candidates
58- 59 I2 --- Nm [0/11]? Number of massive YSO candidates
61- 67 F7.2 arcsec Diam [28/1255] Group/SubGroup diameter
69- 74 F6.2 arcsec e_Diam [0.7/143] Uncertainty in Diam
--------------------------------------------------------------------------------
Note (1): In W51, subgroups identified with dc=51" are named
under the main group with main number and a letter.
In W43, subgroups identified with dc=59" are named
under the main group with an asterisk.
Note (2): Central coordinates of the YSO groups or subgroups.
Note (3): Number of stars with infrared excess. Includes Class I, Class II,
deeply embedded protostars, and transition disk candidates.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1[01].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Seq [1/17] Massive YSO Sequential running number
4- 4 A1 --- f_Seq Flag on Seq; (*) source has 24 micron data
6- 13 A8 --- --- [SSTOERC_]
14- 29 A16 --- SSTOERC IAU name (GLLL.llll+B.bbbb)
31- 40 F10.6 deg RAdeg Right ascension in decimal degrees (J2000)
42- 50 F9.6 deg DEdeg Declination in decimal degrees (J2000)
52- 55 F4.2 10+3Lsun Lum [1/10] MYSO Luminosity
57- 60 F4.2 10+3Lsun e_Lum [0/4] Uncertainty in Lum (1)
62- 66 F5.2 Msun Mass [5/12] MYSO Mass
68- 71 F4.2 Msun e_Mass [0/3] Uncertainty in Mass (1)
73- 73 A1 --- IRAC IRAC population class (2)
75- 75 A1 --- SED SED class (2)
77- 81 F5.2 --- alpha [-0.2/3] SED Slope
83- 86 F4.2 --- e_alpha [0.06/1.2] Uncertainty in alpha
--------------------------------------------------------------------------------
Note (1): Standard deviation of the weighted mean values are reported here.
χ2 values are used to weight the fits. Minimum 10 fits from the
defined best fit criteria was required to calculate the weighted mean
values.
Note (2): Class as follows:
0 = deeply embedded;
1 = Class I;
2 = Class II;
F = Flat spectrum;
3 = transition disks.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: w43cat.dat w51cat.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- --- [SSTOERC_]
9- 24 A16 --- SSTOERC Spitzer identifier (GLLL.llll+B.bbbb) (1)
26- 34 F9.5 deg RAdeg Right ascension (J2000)
36- 43 F8.5 deg DEdeg Declination (J2000)
45- 51 F7.2 mag Jmag [-10/25.9]?=- 2MASS/UKIDSS J-band magnitude
53- 59 F7.2 mag Hmag [-10/24.5]?=- 2MASS/UKIDSS H-band magnitude
61- 67 F7.2 mag Kmag [-10/24.5]?=- 2MASS/UKIDSS K-band magnitude
69- 76 F8.3 mag [3.6] [-10/19]?=- Spitzer/IRAC 3.6um magnitude
78- 85 F8.3 mag [4.5] [-154/19.1]?=- Spitzer/IRAC 4.5um magnitude
87- 94 F8.3 mag [5.8] [-188/17.5]?=- Spitzer/IRAC 5.8um magnitude
96-103 F8.3 mag [8.0] [-10/17.1]?=- Spitzer/IRAC 8.0um magnitude
105-111 F7.2 mag [24] [0.1/10.1]?=- Spitzer/MIPS 24um magnitude
113-118 F6.2 mag e_Jmag [0.02/55]?=- Jmag uncertainty
120-125 F6.2 mag e_Hmag [0.01/26]?=- Hmag uncertainty
127-132 F6.2 mag e_Kmag [0.01/79]?=- Kmag uncertainty
134-140 F7.3 mag e_[3.6] [0/9]?=- [3.6] uncertainty
142-148 F7.3 mag e_[4.5] [0.001/9]?=- [4.5] uncertainty
150-156 F7.3 mag e_[5.8] [0.001/9]?=- [5.8] uncertainty
158-164 F7.3 mag e_[8.0] [0.001/9]?=- [8.0] uncertainty
166-171 F6.2 mag e_[24] [0.02/0.4]?=- [24] uncertainty
173-176 I4 --- Class [-100/99] Classification type (2)
178 I1 --- n_Class [1/2] Method by which they were classified (3)
180-184 F5.2 --- alpha [-4.2/7.2]? SED slope α
186-189 F4.2 --- e_alpha [0/4]?=- alpha uncertainty
191-194 F4.2 --- R2 [0/1]? R-squared value
--------------------------------------------------------------------------------
Note (1): Sources are named according to their Galactic longitude and latitude
with the prefix SSTOERC, referring to Spitzer Space Telescope,
Origin and Evolution of Rich Clusters project.
Note (2): Type as follows:
0 = deeply embedded (W43: 144 occurrences; W51: 56 occurrences),
1 = Class I (W43: 917 occurrences; W51: 302 occurrences),
2 = Class II (W43: 4993 occurrences; W51: 1101 occurrences),
3 = transition disks (W43: 194 occurrences; W51: 77 occurrences),
4 = faint Class I (W43: 303 occurrences; W51: 100 occurrences),
5 = faint Class II (W43: 4549 occurrences; W51: 1618 occurrences),
6 = faint transition disks (W43: 46 occurrences; W51: 35 occurrences),
99 = Class III and photospheres
(W43: 429895 occurrences; W51: 157165 occurrences),
9 = shocked gas emission (W43: 13 occurrences; W51: 5 occurrences),
29 = AGNs (W43: 0 occurrence; W51: 1 occurrence),
19 = PAH galaxies (W43: 86 occurrences; W51: 74 occurrences),
20 = PAH-dominated sources (W43: 1317 occurrences; 444 occurrences),
12 = AGBs (W43: 866 occurrences; W51: 180 occurrences)
-100 = unclassified (W43:198409 occurrences; W51: 124094 occurrences).
Note (3): Sources are flagged according to the method by which they were
classified as follows:
1 = Gutermuth et al. (2009, J/ApJS/184/18) classification,
2 = AGBs, faint YSO elimination method (see Section 2.3).
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 30-Nov-2017