J/ApJ/750/136 Molecular clouds in the Antennae from CO(2-1) (Wei+, 2012)
Two populations of molecular clouds in the Antennae galaxies.
Wei L.H., Keto E., Ho L.C.
<Astrophys. J., 750, 136 (2012)>
=2012ApJ...750..136W 2012ApJ...750..136W
ADC_Keywords: Galaxies, radio ; Molecular clouds ; Velocity dispersion ;
Interstellar medium
Keywords: galaxies: individual (NGC 4038,NGC 4039) - galaxies: ISM -
galaxies: starburst - galaxies: star clusters: general
Abstract:
Super star clusters--extremely massive clusters found predominately in
starburst environments--are essential building blocks in the formation
of galaxies and thought to dominate star formation in the
high-redshift universe. However, the transformation from molecular gas
into these ultracompact star clusters is not well understood. To study
this process, we used the Submillimeter Array and the Plateau de Bure
Interferometer to obtain high angular resolution (∼1.5" or 160pc)
images of the Antennae overlap region in CO(2-1) to search for the
molecular progenitors of the super star clusters. We resolve the
molecular gas distribution into a large number of clouds, extending
the differential cloud mass function down to a 5σ completeness
limit of 3.8x105M☉. We identify a distinct break in the mass
function around log Mmol/M☉~6.5, which separates the
molecular clouds into two distinct populations. The smaller, less
massive clouds reside in more quiescent areas in the region, while the
larger, more massive clouds cluster around regions of intense star
formation. A broken power-law fit to the mass function yields slopes
of α=-1.39±0.10 and α=-1.44±0.14 for the low- and
high-mass cloud population, well matched to the mass function found
for super star clusters in the Antennae galaxies. We find large
velocity gradients and velocity dispersions at the locations of
intense star formation, suggestive of compressive shocks. It is likely
that these environmental factors contribute to the formation of the
observed massive molecular clouds and super star clusters in the
Antennae galaxies.
Description:
The Submillimeter Array (SMA) observations were taken in 2008 May and
2011 February in the compact and extended array configurations,
respectively, with a single pointing with a phase center
(J120154.70-185305.0). The correlator was tuned to the frequency of
CO(2-1) at 230.53799 GHz.
The Plateau de Bure Interferometer (PdBI) observations were taken
between February and April of 2006 in the B and C arrays, respectively.
The correlator was configured to cover the CO(2-1) line with four
windows each 160MHz in width.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 57 132 Cloud catalog (basic properties from clumpfind)
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See also:
J/AJ/140/75 : Antennae galaxies (NGC 4038/4039) revisited (Whitmore+, 2010)
J/ApJ/686/948 : CO in extragalactic giant molecular clouds (Bolatto+, 2008)
J/ApJS/166/211 : Chandra sources in Antennae galaxies (Zezas+, 2006)
J/A+A/443/41 : NGC 4038/4039 broad and narrow band photometry (Mengel+, 2005)
J/ApJ/635/280 : Star clusters in the Antennae galaxies (Brandl+, 2005)
J/AJ/127/660 : Photometry in southern tail of the Antennae (Saviane+, 2004)
J/ApJ/599/1049 : Supergiant molecular complexes in the Antennae (Wilson+, 2003)
J/ApJ/561/727 : BVI photometry in the Antennae galaxies (Zhang+, 2001)
J/AJ/109/960 : Young star clusters in The Antennae (Whitmore+ 1995)
J/ApJ/428/693 : Rosette Nebula and Maddalena Cloud structures (Williams+ 1994)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/132] Running sequence number
5- 6 I2 h RAh [12] Hour of right ascension (J2000)
8- 9 I2 min RAm [1] Minute of right ascension (J2000)
11- 15 F5.2 s RAs [53/56] Second of right ascension (J2000)
17 A1 --- DE- [-] Sign of declination (J2000)
18- 19 I2 deg DEd [18] Degree of declination (J2000)
21- 22 I2 arcmin DEm [52/53] Arcminute of declination (J2000)
24- 27 F4.1 arcsec DEs Arcsecond of declination (J2000)
29- 34 F6.1 km/s Vrad [1328/1787] Velocity (Vrad)
36 A1 --- l_Rad Limit flag on Rad (1)
38- 40 I3 pc Rad [35/317] Radius in parsecs
42 A1 --- l_sigma Limit flag on sigma (1)
44- 47 F4.1 km/s sigma [0.8/26] Velocity dispersion (σV)
49- 51 F3.1 [Msun] logMmol [4.9/8.4] Log of total molecular gas mass
53 A1 --- l_logMvir Limit flag on logMvir
55- 57 F3.1 [Msun] logMvir [4.5/8.1] Log of virial mass
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Note (1): Clouds that were unresolved spatially or in velocity are assigned
upper limits of 80pc in "Rad" and 4.9km/s in "sigma", respectively.
Note that the velocity is defined using the radio
definition (v=cz/(1+z)).
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 10-Dec-2013