J/ApJ/839/113 Molecular clouds with GLIMPSE/MIPSGAL data (Retes-Romero+, 2017)
The star-formation law in Galactic high-mass star-forming molecular clouds.
Retes-Romero R., Mayya Y.D., Luna A., Carrasco L.
<Astrophys. J., 839, 113 (2017)>
=2017ApJ...839..113R 2017ApJ...839..113R
ADC_Keywords: Molecular clouds ; Photometry, infrared ; YSOs ; Stars, masses ;
Carbon monoxide ; Interstellar medium
Keywords: H II regions ; ISM: clouds ; stars: formation
Abstract:
We study the star-formation (SF) law in 12 Galactic molecular clouds
with ongoing high-mass star-formation (HMSF) activity, as traced by
the presence of a bright IRAS source and other HMSF tracers. We define
the molecular cloud (MC) associated with each IRAS source using 13CO
line emission, and count the young stellar objects (YSOs) within these
clouds using GLIMPSE and MIPSGAL 24µm Spitzer databases. The masses
for high-luminosity YSOs (Lbol>10L☉) are determined
individually using pre-main-sequence evolutionary tracks and the
evolutionary stages of the sources, whereas a mean mass of 0.5M☉
was adopted to determine the masses in the low-luminosity YSO
population. The star-formation rate surface density (ΣSFR)
corresponding to a gas surface density (Σgas) in each MC is
obtained by counting the number of the YSOs within successive contours
of 13CO line emission. We find a break in the relation between
ΣSFR and Σgas, with the relation being a power law
(ΣSFR∝ΣgasN) with the index N varying between 1.4
and 3.6 above the break. The Σgas at the break is between
150-360M☉/pc2 for the sample clouds, which compares well with
the threshold gas density found in recent studies of Galactic
star-forming regions. Our clouds treated as a whole lie between the
Kennicutt relation and the linear relation for Galactic and
extra-galactic dense star-forming regions. We find a tendency for the
high- mass YSOs to be found preferentially in dense regions at
densities higher than 1200M☉/pc2 (∼0.25g/cm2).
Description:
All of the 12 selected molecular clouds have GLIMPSE and MIPSGAL
public data available. Typical Spitzer RGB images (3.6um, 8.0um, and
24um) of the resulting sample of clouds are shown in Figure 1, where
the position of the IRAS source is identified.
In order to define the parent molecular cloud that harbors the
high-mass star-forming regions, we used 13CO(J=1-0) emission data
from the Galactic Ring Survey (GRS) database (Jackson+
2006ApJS..163..145J 2006ApJS..163..145J). The survey data have a velocity resolution of
0.21km/s, a typical (1σ) rms sensitivity of ∼0.13K, a main beam
efficiency of ηmb=0.48, and a beam of 46".
The 13CO emission spectra for the line of sight (LOS) to the
selected IRAS sources are shown in Figure 2, where the observed
velocity of the CS(J=2-1) emission line (Bronfman+ 1996, J/A+AS/115/81)
is also marked.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 86 12 General properties of molecular clouds associated
with IRAS sources with UCHII colors
table2.dat 60 12 Physical properties of the sample molecular clouds
table4.dat 110 5903 Photometric and physical properties of the YSOs
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See also:
II/293 : GLIMPSE Source Catalog (I + II + 3D) (IPAC 2008)
II/332 : c2d Spitzer final data release (DR4) (Evans+, 2003)
II/125 : IRAS catalogue of Point Sources, Version 2.0 (IPAC 1986)
VII/114 : Massachusetts-Stony Brook Galactic Plane CO Survey (Clemens+ 1986)
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
J/ApJS/91/347 : A 5-GHz VLA Survey of the Galactic Plane (Becker+ 1994)
J/ApJS/91/659 : Ultracompact HII regions radio images (Kurtz+ 1994)
J/MNRAS/276/57 : IRAS Galactic star-forming regions. II. (Codella+ 1995)
J/ApJS/101/117 : UBVRIJHKLMNQ photometry in Taurus-Auriga (Kenyon+ 1995)
J/A+AS/115/81 : A CS(2-1) survey of UC HII regions (Bronfman+, 1996)
J/A+A/327/325 : Distances of molecular cloud (May+, 1997)
J/MNRAS/291/261 : Methanol maser of IRAS-selected sources (Walsh+ 1997)
J/MNRAS/301/640 : Ultracompact H II regions studies. II. (Walsh+, 1998)
J/A+A/426/97 : SIMBA survey. 1.2-mm/IRAS sources (Faundez+, 2004)
J/ApJ/638/293 : 1.1mm sources in the Perseus Molecular Cloud (Enoch+, 2006)
J/ApJ/676/427 : MIPS and IRAC data on ChaII PMS stars (Alcala+, 2008)
J/ApJ/674/336 : Spitzer observations of NGC 1333 (Gutermuth+, 2008)
J/ApJ/692/973 : Protostars in Perseus, Serpens and Ophiuchus (Enoch+, 2009)
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/699/1092 : Giant molecular clouds (SRBY) (Heyer+, 2009)
J/A+A/501/539 : RMS survey. 6cm observations of YSOs (Urquhart+, 2009)
J/ApJ/723/1019 : Galactic SFR and gas surface densities (Heiderman+, 2010)
J/ApJ/723/915 : BLAST view of Aquila region (Rivera-Ingraham+, 2010)
J/A+A/533/A109 : Pisa pre-main sequence tracks & isochrones (Tognelli+, 2011)
J/AJ/144/31 : Spitzer+2MASS photom. of protostar cand. (Kryukova+, 2012)
J/AJ/144/192 : Spitzer survey of Orion A & B. I. YSOs (Megeath+, 2012)
J/A+A/559/A79 : IRDC APEX/SABOCA observations (Ragan+, 2013)
J/ApJS/220/11 : SEDs of Spitzer YSOs in the Gould Belt (Dunham+, 2015)
J/AJ/149/64 : MIPSGAL 24µm point source catalog (Gutermuth+, 2015)
J/ApJ/806/231 : MISFITS survey: HCO+ obs. of Spitzer YSOs (Heiderman+, 2015)
J/ApJ/813/25 : YSO candidates in W49 observed with Spitzer (Saral+, 2015)
J/A+A/588/A29 : Star formation in massive clumps in Milky Way (Heyer+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- GMC Name of the molecular cloud containing
the IRAS source
6- 15 A10 --- IRAS IRAS name (HHMMm+DDMM; B1950)
17- 21 F5.2 deg GLON Galactic longitude
23- 27 F5.2 deg GLAT Galactic latitude
29- 30 I2 arcmin Size1 Angular Size of the cloud
32 A1 --- --- [x]
34- 35 I2 arcmin Size2 Angular Size of the cloud
37- 40 F4.1 10+3Lsun Liras [0.7/65.1] Bolometric luminosity (1)
42- 45 F4.1 10+3Lsun e_Liras [0.2/20.3] Liras uncertainty (1)
47- 50 F4.1 km/s Vlsr [-4/67] Velocity with respect to the Local
Standard of Rest of the CS source (2)
52- 54 F3.1 km/s DelV [2/8] Line width (2)
56- 58 F3.1 kpc Dist [1/5.4] Kinematical distance (3)
60- 62 F3.1 kpc e_Dist [0.1/0.6] Dist uncertainty
64- 67 F4.2 pc/arcmin Scale [0.2/1.6] Physical scale for an angular
scale of 1'
69- 71 I3 pc2 Area [15/386] Physical area of the cloud (4)
73- 76 F4.2 pc Beam [0.2/1.2] Physical size of the 46" 13CO
beam at the distance of the cloud
78- 81 F4.1 km/s V13CO [-5/66] Peak velocity of the 13CO obtained
in this work
83- 86 F4.1 km/s DelVco [3/11] 13CO line width obtained in this work
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Note (1): Bolometric luminosity and their error based on distance of the IRAS
source using the flux from the IRAS-PSC
(http://irsa.ipac.caltech.edu/Missions/iras.html)
Note (2): Velocity with respect to the Local Standard of Rest of the
CS source and their ΔV from Bronfman+ (1996, J/A+AS/115/81).
Note (3): Kinematical distance (with a percent error of 12%) to the dense clump
associate with the IRAS source from Faundez+ (2004, J/A+A/426/97).
Note (4): Physical area of the cloud above a column density of gas equivalent
to AV=1mag.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- GMC Molecular cloud name
6- 9 F4.2 10+22cm-2 NH2 [1/7] Molecular hydrogen column density
determined from the 13CO line
11- 14 F4.2 10+22cm-2 e_NH2 [0.4/5] NH2 uncertainty
16- 20 F5.2 mag Av [11/72] Visual extinction equivalent to
the derived gas column density
22- 26 F5.2 mag e_Av [5/33] Av uncertainty
28- 32 F5.2 10+4Msun Mvir [0.3/16.1] Cloud mass calculated using
virial equilibrium (see Equation (1))
34- 38 F5.2 10+4Msun e_Mvir [0.2/14] Mvir uncertainty
40- 44 F5.2 10+4Msun Mlte [0.2/13.6] Cloud mass calculated using
local thermodynamical equilibrium
(see Equation (2))
46- 49 F4.2 10+4Msun e_Mlte [0.1/7] Mlte uncertainty
51- 55 F5.2 10+4Msun Mxf [0.3/20] Cloud mass calculated using
the X-factor (see Equation (4))
57- 60 F4.2 10+4Msun e_Mxf [0.2/10] Mxf uncertainty
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- GMC Molecular cloud name (1)
5 A1 --- --- [-]
6- 9 A4 --- Name MIPSGAL/GLIMPSE YSO identifier (1)
11- 18 F8.5 deg GLON Galactic longitude
20- 27 F8.5 deg GLAT Galactic latitude
29- 33 F5.2 mag 3.6mag [6.7/15.3]?=-1 Spitzer/IRAC 3.6um magnitude (2)
35- 39 F5.2 mag e_3.6mag [0.02/0.4]?=-1 Uncertainty in 3.6mag
41- 45 F5.2 mag 4.5mag [6/14.6]?=-1 Spitzer/IRAC 4.5um magnitude (2)
47- 51 F5.2 mag e_4.5mag [0.02/0.4]?=-1 Uncertainty in 4.5mag
53- 57 F5.2 mag 5.8mag [4/16]?=-1 Spitzer/IRAC 5.8um magnitude (2)
59- 63 F5.2 mag e_5.8mag [0.02/1.2]?=-1 Uncertainty in 5.8mag
65- 69 F5.2 mag 8.0mag [4/13.5]?=-1 Spitzer/IRAC 8.0um magnitude (2)
71- 75 F5.2 mag e_8.0mag [0.02/0.3]?=-1 Uncertainty in 8.0mag
77- 81 F5.2 mag 24mag [-0.9/10.3]?=-1 Spitzer/MIPS 24um magnitude (3)
83- 87 F5.2 mag e_24mag [0/0.6]?=-1 Uncertainty in 24mag
89- 89 I1 --- C [0/3] IR spectral classification (4)
91- 95 F5.2 [-] logbeta [-3.3/-1.3]?=-1 Log β value (5)
97-101 F5.2 [Lsun] logLb [-1.3/6.3]?=-1 Log bolometric luminosity (6)
103-107 F5.2 Msun Mass [0.5/37]?=-1 Mass (6)
109-110 I2 --- H [-1/1]? Flag indicating whether YSO has high
luminosity (7)
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Note (1): The name includes two parts, the first part is the name of the cloud,
and the second part starts with a letter M or G (M indicates detected
in MIPSGAL, and G indicates detected only in GLIMPSE), followed by
the source number. The GLIMPSE-only detected sources do not have
24 micron related quantities, and hence a value of "-1.00" is assigned
for these source's photometry, and the quantities that are derived
from these photometry.
Note (2): From GLIMPSE survey.
Note (3): Spitzer/MIPS 24 micron band magnitude; see Section 3.1.
Note (4): Numbers 0,1,2,3 stand for Class 0, I, II and III, respectively;
Note (5): β value is defined in Section 4.2.1 and Figure 3.
Note (6): Derivated as explained in Section 4.2. The errors on Lbol and mass
are roughly 30%.
Note (7): Flag as follows:
1 = YSO with Lbol≥10 LSun;
0 = YSO with Lbol<10 LSun;
-1 = Unknown.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 05-Dec-2017