J/ApJS/225/26 Very Low-Luminosity Objects (VeLLOs) from 1.25-850um (Kim+, 2016)
A search for very low-luminosity objects in Gould Belt clouds.
Kim M.-R., Lee C.W., Dunham M.M., Evans II N.J., Kim G., Allen L.E.
<Astrophys. J. Suppl. Ser., 225, 26-26 (2016)>
=2016ApJS..225...26K 2016ApJS..225...26K (SIMBAD/NED BibCode)
ADC_Keywords: Photometry, infrared ; Molecular clouds ;
Millimetric/submm sources
Keywords: catalogs; infrared: ISM; stars: formation
Abstract:
We present the results of a search for Very Low-Luminosity Objects
(VeLLOs) in the Gould Belt (GB) clouds using infrared and
sub-millimeter (sub-mm) data from 1.25 to 850µm and our
N2H+(J=1-0) observations. We modified the criteria by Dunham et
al. (2008, J/ApJS/179/249) to select the VeLLOs in the GB clouds,
finding 95 VeLLO candidates, 79 of which are newly identified in this
study. Out of 95 sources, 44 were detected in both sub-mm continuum
and N2H+ emission and were classified as Group A (the VeLLOs), and
51 sources detected in either sub-mm emission or N2H+ emission
were classified with Group B as candidate VeLLOs. We find that these
VeLLOs and the candidates are forming in environments different from
those of the likely VeLLOs. Seventy-eight sources are embedded within
their molecular clouds, and thus are likely VeLLOs forming in a dense
environment. The remaining 17 sources are located in low-level
extinction regions (AV<1) connected to the clouds, and can be either
background sources or candidate substellar objects forming in an
isolated mode. The VeLLOs and the candidates are likely more luminous
and their envelopes tend to be more massive in denser environments.
The VeLLOs and the candidates are more populous in the clouds where
more YSOs form, indicating that they form in a manner similar to that
of normal YSOs. The bolometric luminosities and temperatures of the
VeLLOs are compared to predictions of episodic accretion models,
showing that the low luminosities for most VeLLOs can be well
explained by their status in the quiescent phases of a cycle of
episodic mass accretion.
Description:
The Spitzer Gould Belt Survey (GBS) is a project to survey about 21
square degrees of 11 nearby molecular clouds at 3.6-160um to provide a
census of star formation in nearby large clouds (P.I. L. Allen).
Spitzer has mapped a total of 11 molecular clouds, CMC, Chamaeleon I,
Chamaeleon III, Musca, Lupus V, Lupus VI, Ophiuchus North, Aquila,
CrA, Cepheus, and IC 5146 with the IRAC and MIPS between 2004 March
and 2008 October.
We utilized the data provided by the c2d/GBS projects (Evans et al.
2009, J/ApJS/181/321; Dunham et al. 2015, J/ApJS/220/11).
There are two cloud complexes which were not listed in the c2d/GBS
projects, but observed by other projects, the Taurus molecular clouds
and the Orion molecular clouds. The Taurus molecular clouds have been
observed over an area of ∼44 square degrees by one of the GTO programs
(P.I. D. Padgett) with the IRAC and the MIPS instruments. The Orion
molecular clouds have been surveyed in ∼9°2 area by Spitzer
(P.I. T. Megeath).
See section 2.1 for further details.
Complementary archive infrared data were retrieved from 2MASS and
Herschel PACS and SPIRE and JCMT SCUBA-2; see section 2.2.
We observed our sources with the N2H+(1-0) line with the Korean
Very Long Baseline Interferometry Network (KVN) 21m radio telescopes
from 2011 October to 2016 May for the northern hemisphere sources, and
the Mopra 22m telescope in 2012 April for the southern hemisphere
sources. See section 2.3 for further explanations.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
vellosa.dat 103 44 *The group A VeLLOs; table added by CDS
from physical parameters given in last column
of table 2 in the paper
groupb.dat 103 34 *The group B VeLLO candidates; table added by CDS
from physical parameters given in last column
of table 3 in the paper
typeiii.dat 104 17 The type III VeLLO candidates; table added by CDS
from physical parameters given in last column
of table 4 in the paper
table1.dat 56 30 The Gould Belt molecular clouds searched
for VeLLO candidates
table2.dat 75 544 *List of the VeLLOs (Group A) fluxes
table3.dat 75 334 *List of the VeLLO candidates (Group B) fluxes
table4.dat 75 159 List of Type III VeLLO candidates fluxes
table5.dat 183 97 *List of Group C VeLLO candidates
--------------------------------------------------------------------------------
Note on vellosa.dat and table2.dat: Sources in Group A are sources which passed
the selection criteria described in section 3.2 and are detected in both dust
continuum and N2H+ emission.
Note on groupb.dat and table3.dat: Group B sources are those that also pass the
selection criteria described in section 3.2 and are detected either in dust
continuum or N2H+ emission, but not both.
Note on table5.dat: Group C sources also pass the selection criteria described
in section 3.2, but lack the necessary observations or detections to determine
if they are associated with sub-millimeter continuum or N2H+ emission.
--------------------------------------------------------------------------------
See also:
II/332 : c2d Spitzer final data release (DR4) (Evans+, 2003)
J/ApJ/817/167 : JCMT Gould Belt Survey: dense cores in Orion B (Kirk+, 2016)
J/A+A/584/A91 : Dense cores in Aquila from Herschel (Konyves+, 2015)
J/MNRAS/448/1551 : JCMT Gould Belt Survey: Serpens MWC 297 (Rumble+, 2015)
J/ApJ/786/29 : Catalog of distances to molecular clouds (Schlafly+, 2014)
J/ApJ/767/36 : APEX observations of HOPS protostars (Stutz+, 2013)
J/AJ/145/94 : Protostar luminosities from Spitzer surveys (Dunham+, 2013)
J/ApJS/205/5 : YSO candidates in nearby molecular clouds (Hsieh+, 2013)
J/AJ/144/192 : Spitzer survey of Orion A & B. I. YSO catalog (Megeath+, 2012)
J/AJ/144/31 : Spitzer+2MASS photometry of protostar cand. (Kryukova+, 2012)
J/A+A/527/A145 : Chamaeleon I 870um sources (Belloche+, 2011)
J/PASJ/63/S1 : Atlas & catalog of dark clouds based on 2MASS (Dobashi+, 2011)
J/ApJ/723/1019 : Galactic SFR and gas surface densities (Heiderman+, 2010)
J/ApJS/186/259 : Taurus Spitzer survey: new candidate members (Rebull+, 2010)
J/ApJS/185/198 : The Cepheus flare observed with IRAC and MIPS (Kirk+, 2009)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/ApJS/181/321 : Properties of Spitzer c2d dark clouds (Evans+, 2009)
J/ApJS/179/249 : Low-luminosity embedded protostar population (Dunham+, 2008)
J/A+A/487/993 : MAMBO Mapping of c2d Clouds and Cores (Kauffmann+, 2008)
J/ApJS/177/551 : Spitzer c2d survey of Lupus dark clouds (Merin+, 2008)
J/AJ/136/18 : LMC SAGE. New candidate YSOs (Whitney+, 2008)
J/ApJ/676/427 : MIPS and IRAC data on ChaII PMS stars (Alcala+, 2008)
J/ApJ/663/1149 : Spitzer survey of Serpens YSO population (Harvey+, 2007)
J/AJ/133/1560 : Spitzer c2d small clouds and cores (Wu+, 2007)
J/ApJ/638/293 : 1.1mm sources in the Perseus Molecular Cloud (Enoch+, 2006)
J/A+A/447/609 : 1.2mm continuum observations in rho Oph cloud (Stanke+, 2006)
J/ApJS/115/59 : Cepheus flare molecular clouds (Kun, 1998)
J/A+A/291/943 : Protostellar cores (Ossenkopf+, 1994)
J/A+A/216/44 : Walraven photometry in Sco-Cen association (De Geus+, 1989)
Byte-by-byte Description of file: vellosa.dat groupb.dat typeiii.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Seq [1/95] Sequential running number
4- 19 A16 --- Name Spitzer source name
(JHHMMSS.s+DDMMSS or other)
21- 36 A16 --- Cloud Gould Belt molecular cloud identifier
(as in table 1)
38- 42 F5.3 Lsun Lint [0.002/0.3]? Internal luminosity
inferred from 70um flux
44- 48 F5.3 Lsun e_Lint [0.001/0.06]? Lint uncertainty
50- 52 I3 K Tbol [16/758] Bolometric temperature
54- 58 F5.3 Lsun Lbol [0.002/1.8] Bolometric temperature
60- 63 F4.1 K Tdust [10/40] Dust temperature
65- 66 A2 --- l_TMB [≤] Limit flag on TMB
67- 70 F4.2 K TMB [0.2/5.1]? Peak main beam temperature
(N2H+(1-0)) (not for type III sources)
72- 75 F4.2 K e_TMB [0.07/0.5]? TMB uncertainty
77- 80 F4.2 km/s delV [0.2/1]? N2H+_ line velocity
(ΔVN2H+^_) (only for group A)
82- 85 F4.2 km/s e_delV [0.01/0.4]? delV uncertainty
87- 92 F6.4 Msun Menv [0.0001/0.9]? Mass of the envelope
94- 95 I2 arcsec R250 [24/67]? Geometric mean of the major and
minor axes of the FWHM of source envelope at
250um extracted by CSAR
97-104 A8 --- Type Type I, II or III (1)
--------------------------------------------------------------------------------
Note (1): We examined how the VeLLO candidates are distributed in our AV maps,
finding that they have the characteristic spatial distributions as
shown in Figure 3; they are typically located
(1) within AV=7.3 (Type I),
(2) between contours of AV=7.3 and AV=1 (Type II), or
(3) outside the clouds (AV<1; Type III).
See section 4.1 for further explanations.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- f_Cloud [c] c=small core
3- 18 A16 --- Cloud Gould Belt molecular cloud or small cores
20- 26 A7 --- Project Project identifier
28- 30 I3 pc Dist [125/450] Distance
(or lower range if Dist2 exists)
31 A1 --- --- [-]
32- 34 I3 pc Dist2 [325]? Upper range of Distance
36- 38 I3 pc e_Dist [2/100]? Distance uncertainty
40- 41 I2 --- r_Dist [1/16] Distance reference (1)
43- 46 I4 --- Nyso [4/3479]? Number of YSOs (2)
48- 49 I2 --- NV [0/28] Number of VeLLOs from this study
51- 54 F4.1 --- Av [2.1/12.4]? V-band extinction
56 I1 --- r_Av [1/4]? Av reference (3)
--------------------------------------------------------------------------------
Note (1): Reference as follows:
1 = Enoch et al. (2006ApJ...638..293E 2006ApJ...638..293E)
2 = Lada et al. (2009ApJ...703...52L 2009ApJ...703...52L)
3 = Rebull et al. (2010, J/ApJS/186/259)
4 = Belloche et al. (2011, J/A+A/527/A145)
5 = Whittet et al. (1997A&A...327.1194W 1997A&A...327.1194W)
6 = Knude & Hog (1998A&A...338..897K 1998A&A...338..897K)
7 = Comeron F. (2008hsf2.book..295C 2008hsf2.book..295C)
8 = Maury et al. (2011A&A...535A..77M 2011A&A...535A..77M)
9 = de Geus et al. (1989, J/A+A/216/44)
10 = Wilking et al. (2008hsf2.book..351W 2008hsf2.book..351W)
11 = Dzib et al. (2011RMxAC..40..231D 2011RMxAC..40..231D)
12 = Neuhauser & Forbrich (2008hsf2.book..735N 2008hsf2.book..735N)
13 = Maheswar et al. (2016 in preparation)
14 = Kirk et al. (2009, J/ApJS/185/198)
15 = Schlafly et al. (2014, J/ApJ/786/29)
16 = Dunham et al. (2008, J/ApJS/179/249).
Note (2): NYSOs are from Heiderman et al. (2010, J/ApJ/723/1019), except for
those for Taurus and Lupus cloud which are from
Rebull+ (2010, J/ApJS/186/259) and Rygl+ (2013A&A...549L...1R 2013A&A...549L...1R),
respectively.
Note (3): References for the averaged-visual extinction in the clouds
as follows:
1 = Evans et al. (2009, J/ApJS/181/321),
2 = Dunham et al. (2013, J/AJ/145/94),
3 = this study, and
4 = Spezzi et al. (2011ApJ...730...65S 2011ApJ...730...65S).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table[234].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Seq [1/95] Source number (1-44 for group A (table2),
45-78 for group B (table3) and
79-95 for Type III (table4))
4- 20 A17 --- Name Spitzer source name
21- 21 A1 --- Flag [d] Protobinary candidate flag (1)
24- 31 F8.2 um lambda [0.75/33000]? Wavelength
33- 36 A4 --- l_FD [≤] Limit flag on FD
37- 47 F11.5 mJy FD [0.0004/90020]? Flux density at lambda (2)
49- 57 F9.3 mJy e_FD [0/16100]? Uncertainty in FD
59 A1 --- f_FD [d] Protobinary candidate flag on FD (1)
61- 72 A12 --- Inst ? Instrument used
74- 75 I2 --- Ref ? Reference (3)
--------------------------------------------------------------------------------
Note (1):
d = Indicates that this source is a possible protobinary and its image is
blended at the 500 micron wavelength. In this case we listed halves of
the 500 micron fluxes for these sources obtained from CSAR.
Note (2): All the fluxes at 2MASS, IRAC, and MIPS1 bands are
extinction-corrected. For non-detection sources, 3σ upper
limits of their fluxes are given.
Note (3): Reference as follows:
1 = This study;
2 = Dunham et al. (2008, J/ApJS/179/249);
3 = Enoch et al. (2006, J/ApJ/638/293);
4 = Palau et al. (2014MNRAS.444..833P 2014MNRAS.444..833P);
5 = Andre et al. (1999ApJ...513L..57A 1999ApJ...513L..57A);
6 = Kirk et al. (2005MNRAS.360.1506K 2005MNRAS.360.1506K);
7 = Young et al. (2006AJ....132.1998Y 2006AJ....132.1998Y);
8 = Kauffmann et al. (2008, J/A+A/487/993);
9 = Andre & Montmerle (1994ApJ...420..837A 1994ApJ...420..837A);
10 = Young et al. (2006ApJ...644..326Y 2006ApJ...644..326Y);
11 = Stanke et al. (2006, J/A+A/447/609);
12 = Wu et al. (2007, J/AJ/133/1560);
13 = Lee et al. (2009ApJ...693.1290L 2009ApJ...693.1290L);
14 = Kun (1998, J/ApJS/115/59);
15 = Young et al. (2004ApJS..154..396Y 2004ApJS..154..396Y);
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Seq [1/97] Source number
4- 19 A16 --- Name Spitzer source name; JHHMMSS.s+DDMMSS
21- 36 A16 --- Cloud Cloud identifier (as in table 1)
38- 41 A4 --- l_FD1.25 [≤] Limit flag on F1.25
42- 48 F7.2 mJy FD1.25 [0.4/115]? 2MASS 1.25um band (J) flux density
50- 53 F4.2 mJy e_FD1.25 [0.01/4]? The 1σ uncertainty in F1.25
55- 60 F6.2 mJy FD1.65 [0.3/314]? 2MASS 1.65um band (H) flux density
62- 65 F4.2 mJy e_FD1.65 [0.01/7]? The 1σ uncertainty in F1.65
67- 70 A4 --- l_FD1.65 [≤] Limit flag on F1.65
71- 76 F6.2 mJy FD2.12 [0.7/618]? 2MASS 2.12um band (KS) flux density
78- 82 F5.2 mJy e_FD2.12 [0.1/15]? The 1σ uncertainty in F2.12
85- 86 A2 --- l_FD2.12 [≤] Limit flag on F2.12
87- 93 F7.2 mJy FD3.6 [0.09/1073]? Spitzer/IRAC 3.6um band flux density
95- 99 F5.2 mJy e_FD3.6 [0.01/55]? The 1σ uncertainty in F3.6
101-104 A4 --- l_FD3.6 [≤] Limit flag on F3.6
105-111 F7.2 mJy FD4.5 [0.1/1443]? Spitzer/IRAC 4.5um band flux density
113-117 F5.2 mJy e_FD4.5 [0.01/75]? The 1σ uncertainty in F4.5
119-122 A4 --- l_FD4.5 [≤] Limit flag on F4.5
123-129 F7.2 mJy FD5.8 [0.1/1811]? Spitzer/IRAC 5.8um band flux density
131-135 F5.2 mJy e_FD5.8 [0.03/88]? The 1σ uncertainty in F5.8
137-143 F7.2 mJy FD8.0 [0.01/2553]? Spitzer/IRAC 8.0um band flux density
145-148 F4.2 mJy e_FD8.0 [0.04/5]? The 1σ uncertainty in F8.0
150-155 F6.1 mJy FD24 [0.5/4264] Spitzer/MIPS 24um band flux density
157-161 F5.1 mJy e_FD24 [0/446] The 1σ uncertainty in F24
163-166 I4 mJy FD70 [8/5320] Spitzer/MIPS 70um band flux density
168-171 I4 mJy e_FD70 [0/573]? The 1σ uncertainty in F70
173-177 F5.3 Lsun LInt [0.001/0.3] Integrated luminosity
179-183 F5.3 Lsun e_LInt [0.001/0.1] The 1σ uncertainty in LInt
--------------------------------------------------------------------------------
Acknowledgments:
Mi-Ryang Kim < koon 7680 {at} gmail dot com > for the coordinates of
source #13 ("CB130-3") in sources.dat file and distance in table1.dat of
CG 30-31.
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 18-Oct-2016