J/ApJ/876/141 ALMA obs. of giant molecular clouds in Hen 2-10 (Imara+, 2019)
ALMA observations of giant molecular clouds in the starburst dwarf galaxy
Henize 2-10.
Imara N., Faesi C.M.
<Astrophys. J., 876, 141 (2019)>
=2019ApJ...876..141I 2019ApJ...876..141I
ADC_Keywords: Molecular clouds; Velocity dispersion; Carbon monoxide
Keywords: galaxies: dwarf; galaxies: individual (He 2-10); galaxies: starburst;
galaxies: star formation; ISM: clouds; ISM: molecules
Abstract:
We present new 12CO (J=1-0) observations of He 2-10, a blue compact
dwarf galaxy about 8.7Mpc away, taken with the Atacama Large
Millimeter Array. These are the highest spatial and spectral
resolution observations, to date, of the molecular gas in this
starburst galaxy. We measure a molecular mass of
(1.2±0.4)x108M☉ in He 2-10, and 75% of the molecular gas
mass is contained within the northern region of the galaxy near the
previously identified young super star clusters, which has a projected
size of about 300pc. We use the CPROPS algorithm to identify 119
resolved giant molecular clouds distributed throughout the galaxy, and
the molecular gas contained within these clouds makes up between 45%
and 70% of the total molecular mass. The molecular clouds in He 2-10
have similar median sizes (∼26pc), luminous masses (∼4x105M☉),
and surface densities (∼180M☉/pc2) to Milky Way clouds.
However, He 2-10 clouds have velocity dispersions (∼3km/s) about 50%
higher than those in the Milky Way. We provide evidence that He 2-10
clouds tend to be in virial equilibrium, with the virial and luminous
masses scaling according to Mvir∝Mlum1.2±0.1, similar
to clouds in the Milky Way. However, we measure a scaling relationship
between luminous mass and size, Mlum∝R3.0±0.3, that is
steeper than what is observed in Milky Way clouds. Assuming that
He 2-10 molecular clouds are virialized, we infer values of the
CO-to-H2 conversion factor ranging from 0.5 to 13 times the standard
value in the solar neighborhood. Given star formation efficiencies as
low as 5%, the most massive molecular clouds in He 2-10 currently have
enough mass to form the next generation of super star clusters in the
galaxy.
Description:
We obtained ALMA Cycle 4 observations (project code 2015.1.01569.S;
PI: Nia Imara) in the CO (1-0) line at 115.2712GHz toward He 2-10 in
2016 July 31 and August 2. A single position (RAJ2000=08:36:15.20,
DEJ2000=-26:24:34.0) was observed. The ALMA 12m array was in
configuration C36-4 for the two observing nights, with 36 antennas
each night, arranged with baselines from 15 to 1124m, implying a
minimum angular resolution of 0.48" and a maximum recoverable scale of
6.7" (at 115.27GHz).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 75 119 Properties of He 2-10 giant molecular clouds (GMCs)
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See also:
IX/57 : The Chandra Source Catalog (CSC), Release 2.0 (Evans+, 2019)
J/ApJS/63/821 : Inner Galaxy Molecular clouds & cloud cores (Scoville+, 1987)
J/ApJ/428/693 : Rosette Nebula and Maddalena Cloud structures (Williams+ 1994)
J/A+AS/139/1 : HI in Byurakan blue compact galaxies (Thuan+, 1999)
J/ApJ/551/852 : FCRAO CO survey of the outer Galaxy (Heyer+, 2001)
J/ApJ/654/240 : Giant molecular clouds in M31 (Rosolowsky+, 2007)
J/ApJ/686/948 : CO in extragalactic giant molecular clouds (Bolatto+, 2008)
J/ApJS/181/321 : Properties of Spitzer c2d dark clouds (Evans+, 2009)
J/ApJ/699/1092 : Giant molecular clouds (SRBY) (Heyer+, 2009)
J/ApJS/197/16 : CO observations of LMC molecular clouds (MAGMA). (Wong+, 2011)
J/A+A/542/A108 : Giant molecular clouds in M33 (Gratier+, 2012)
J/ApJ/784/3 : The PAWS catalogs of GMCs and islands in M51 (Colombo+, 2014)
J/ApJ/803/16 : GMCs in NGC4526 based on 12CO (Utomo+, 2015)
J/ApJ/829/93 : CO, [CI] & [NII] lines from Herschel (Kamenetzky+, 2016)
J/A+A/604/A101 : MUSE datacube of He 2-10 (Cresci+, 2017)
J/ApJ/857/19 : ALMA view of GMCs in NGC 300 (Faesi+, 2018)
J/ApJ/860/172 : Cloud-scale molecular gas data in 15 galaxies (Sun+, 2018)
J/ApJ/867/165 : CO molecular clumps in Henize 2-10 dwarf galaxy (Beck+, 2018)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/119] Running sequence number;
<[IF2019] He 2-10 NNN> in Simbad
5- 6 I2 h RAh Hour of right ascension (J2000)
8- 9 I2 min RAm Minute of right ascension (J2000)
11-15 F5.2 s RAs Second of right ascension (J2000)
17 A1 --- DE- Sign of declination (J2000)
18-19 I2 deg DEd Degree of declination (J2000)
21-22 I2 arcmin DEm Arcminute of declination (J2000)
24-27 F4.1 arcsec DEs Arcsecond of declination (J2000)
29-33 F5.1 km/s Vel0 [787.6/906.1] Velocity
35-38 F4.1 pc Rad [5.3/76.7] Projected radius R
40-43 F4.1 pc e_Rad [1.8/13.6] Rad uncertainty
45-48 F4.1 km/s sigV [1/10.1] One-dimensional velocity dispersion
(σv)
50-52 F3.1 km/s e_sigV [0.2/1.9] SigV uncertainty
54-57 F4.1 10+5Msun Mlum [0.4/51.1] Luminous mass
59-61 F3.1 10+5Msun e_Mlum [0.2/3.2] Mlum uncertainty
63-66 F4.1 10+5Msun Mvir [0.1/76] Virial mass
68-70 F3.1 10+5Msun e_Mvir [0.1/9.3] Mvir uncertainty
72-75 F4.1 K Tmax [3.9/13.9] Maximum temperature
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 19-Nov-2020