J/ApJ/964/166 Molecular clouds from ALMA in Antennae gal. overlap (Krahm+, 2024)
Physical properties of molecular clouds in the overlap region of the merging
Antennae Galaxies.
Krahm G., Finn M.K., Indebetouw R., Johnson K.E., Kamenetzky J., Bemis A.
<Astrophys. J., 964, 166 (2024)>
=2024ApJ...964..166K 2024ApJ...964..166K
ADC_Keywords: Galaxies, interacting; Carbon monoxide; Molecular clouds;
Interstellar medium
Keywords: Starburst galaxies ; Galaxy mergers ; Galaxy interactions ;
Interstellar medium ; Molecular clouds ; Star formation ;
Millimeter astronomy
Abstract:
As the closest major galaxy merger and home to thousands of super star
clusters (SSCs), the Antennae Galaxies (NGC 4038 and NGC 4039) are an
important location to study the molecular clouds at sites of vigorous
star formation. We cataloged giant molecular clouds (GMCs) in the
region where the two galaxies overlap using high-resolution
(∼0.1"-10pc) Atacama Large Millimeter/submillimeter Array observations
of the 12CO(2-1) and 13CO(2-1) emission lines. Of the 72 individual
GMCs identified in the overlap region, 17 are within uncertainties of
having the necessary mass, pressure, and size needed to form SSCs. Of
those 17 GMCs, only one has significant ionizing radiation, indicating
that the birth environments are likely still intact in the 16 other
GMCs. We compared the physical properties calculated from 12CO(2-1)
GMC data with observations of 10 other galaxies obtained using the
same emission line and similar resolution. Compared to other sources
in this sample, the GMCs from the Antennae, as well as in other
starbursts and in the centers of galaxies, have the highest
luminosities, surface densities, and turbulent pressures. The GMCs in
starbursts and at the centers of galaxies also have large line widths,
although the line widths in the Antennae are among the widest. These
comparative results also indicate that the Antennae GMCs have the
highest virial parameters despite their high densities.
Description:
We used ALMA data from projects 2015.1.00977.S and 2016.1.00924.S
during Cycles 3 and 4. This includes Band 6 and 7 observations of the
12CO(2-1), 13CO(2-1), and 12CO(3-2) emission lines focused on the
Antennae overlap region.
The area of observation with the 12(2-1) observations are shown in
Figure 1.
In addition to the CO emission lines from ALMA, we also used archival
3.6cm (8.46GHz) radio continuum data (project AN074) taken in 1997
with the Karl G. Jansky Very Large Array (VLA) at the X band in the A
configuration.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 215 72 12CO(2-1) Clump properties
tablea2.dat 200 72 13CO(2-1) Clump properties
tablea3.dat 221 206 12CO(2-1) Dendrogram properties
tablea4.dat 206 206 13CO(2-1) Dendrogram properties
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See also:
J/AJ/109/960 : Young star clusters in The Antennae (Whitmore+ 1995)
J/ApJ/559/864 : Extragalactic ultracompact H II regions (Johnson+, 2001)
J/ApJ/671/333 : Aperture photometry in NGC 5194 (Kennicutt+, 2007)
J/ApJ/654/240 : Giant molecular clouds in M31 (Rosolowsky+, 2007)
J/ApJ/661/830 : Giant molecular clouds of M33 (Rosolowsky+, 2007)
J/ApJ/699/1092 : Giant molecular clouds (SRBY) (Heyer+, 2009)
J/AJ/140/75 : Antennae galaxies (NGC4038/4039) revisited (Whitmore+, 2010)
J/ApJ/750/136 : Molecular clouds in the Antennae from CO(2-1) (Wei+, 2012)
J/ApJ/774/73 : ALMA CO observations of 30 Dor (Indebetouw+, 2013)
J/MNRAS/435/400 : ATLASGAL. Compact HII regions (Urquhart+, 2013)
J/A+A/563/A97 : IRAM 30m reduced spectra of 59 sources (Gerner+, 2014)
J/MNRAS/445/1412 : HII regions & GMC in the Antennae (Zaragoza-Cardiel+, 2014)
J/ApJ/803/16 : GMCs in NGC4526 based on 12CO (Utomo+, 2015)
J/ApJ/867/165 : CO mol. clumps in Henize 2-10 dwarf galaxy (Beck+, 2018)
J/ApJ/864/120 : ALMA obs. toward NGC 5253. I. MoCs (Miura+, 2018)
J/ApJ/876/141 : ALMA obs. of GMCs in Hen 2-10 (Imara+, 2019)
Byte-by-byte Description of file: tablea[12].dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq [1/72] Giant molecular cloud ID number
4 I1 --- Type [2] Type of structure (always 2:
quickclump clump or dendrogram leaf)
6- 7 I2 h RAh [12] Right ascension in hours (J2000)
9- 10 I2 min RAm [1] Right ascension in minutes (J2000)
12- 18 F7.4 s RAs Right ascension in seconds (J2000)
20 A1 --- DE- [-] Sign of declination (J2000)
21- 22 I2 deg DEd [18] Declination in degrees (J2000)
24- 25 I2 arcmin DEm [53] Declination in arcminutes (J2000)
27- 33 F7.4 arcsec DEs Declination in arcseconds (J2000)
35- 37 I3 --- SGMC [1/345] Supergiant molecular cloud to
which GMC is a part as defined
by Wilson+ 2000ApJ...542..120W 2000ApJ...542..120W
39- 46 E8.2 K.pc2.km/s LCO [78/7360000] CO luminosity
48- 53 F6.2 K.pc2.km/s e_LCO [11/443] Uncertainty in LCO
55- 59 F5.2 K Tpeak [1/35] Peak brightness temperature, CO max
61- 68 E8.2 Msun Mlum [52700/2.12e+7] Luminous mass calculated
with H2-to-CO conversion factor
70- 77 E8.2 Msun e_Mlum [5270/2.12e+6] Uncertainty in Mlum
79- 84 F6.3 --- LR [0.9/26.4] Line ratio from observed line
to 12CO(1-0)
86- 91 F6.3 km/s sigV [2.4/48.1] Velocity dispersion, σv
93- 98 F6.4 km/s e_sigV [0.1/2.4] Uncertainty in sigV
100- 105 F6.3 pc maj [6.4/66.5] Major axis of ellipse fitted
to HWHM of clump
107- 112 F6.3 pc min [1/47.8] Minor axis of ellipse fitted to
HWHM of clump
114- 119 F6.3 pc Rad [0.5/85]? Radius, R
121- 127 F7.4 pc e_Rad [1.5/97]? Uncertainty in Rad
129- 135 F7.1 pc2 Area [6/23500] Full area
137- 142 F6.1 pc Perim [103/1359] Perimeter
144- 152 F9.2 Msun/pc2 Sigma [53.8/499000]? Surface density Σ
using Mlum and Rad
154- 166 F13.3 Msun/pc2 e_Sigma [5.7/5.13e+8]? Uncertainty in Sigma
168- 175 E8.2 K/cm3 Pe [199000/2.84e+11]? Pressure as defined by
Equation 13 (G1)
177- 184 E8.2 K/cm3 e_Pe [357000/1.55e+14]? Uncertainty in Pe
186- 192 F7.4 [-] logaVir [0.2/42.4]? Virial parameter as defined
by Equation 12 (avir=
(R{sgima}v2R)/GM)
194- 200 F7.4 [-] e_logaVir [0.2/42]? Uncertainty in alphavir
202- 209 E8.2 Msun MLTE [59500/11400000]? Local thermodynamic
equilibrium (LTE) mass (only for Table A1)
211- 215 F5.2 K Tex [13.26/25.22]? Excitation temperature
(only for Table A1)
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Byte-by-byte Description of file: tablea[34].dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [0/205] Giant Molecular Cloud ID number
5 I1 --- Type [0/2]? Type of structure (1)
7- 8 I2 h RAh [12] Right ascension in hours (J2000)
10- 11 I2 min RAm [1] Right ascension in minutes (J2000)
13- 19 F7.4 s RAs Right ascension in seconds (J2000)
21 A1 --- DE- [-] Sign of declination (J2000)
22- 23 I2 deg DEd [18] Declination in degrees (J2000)
25- 26 I2 arcmin DEm [53] Declination in arcminutes (J2000)
28- 34 F7.4 arcsec DEs Declination in arcseconds (J2000)
36- 38 I3 --- SGMC [1/345] SGMC to which GMC is a part as
defined by Wilson+ 2000ApJ...542..120W 2000ApJ...542..120W
40- 47 E8.2 K.pc2.km/s LCO [78/5.73e+7] CO luminosity
49- 55 F7.2 K.pc2.km/s e_LCO [2/1105] Uncertainty in LCO
57- 61 F5.2 K Tpeak [1/34.8] Peak brightness temperature
63- 70 E8.2 Msun Mlum [27300/1.62e+8] Luminous mass calculated
with H2-to-CO conversion factor
72- 79 E8.2 Msun e_Mlum [55/1.62e+7] Uncertainty in Mlum
81- 86 F6.3 --- LR [0.9/26.4] Line ratio from observed line
to 12CO (1-0)
88- 94 F7.3 km/s sigV [2.7/132]? Velocity dispersion, σv
96- 102 F7.5 km/s e_sigV [0.07/9.2]? Uncertainty in sigV
104- 110 F7.3 pc maj [5.8/259.2] Major axis of ellipse fitted
to HWHM of clump
112- 118 F7.3 pc min [4.7/218] Minor axis of ellipse fitted to
HWHM of clump
120- 126 F7.3 pc Rad [2.7/263]? Radius, R
128- 135 F8.4 pc e_Rad [1.6/151.1]? Uncertainty in Rad
137- 144 E8.2 pc2 Area [2/189000] Full area
146- 152 F7.2 pc Perim [23/6705] Perimeter
154- 161 F8.2 Msun/pc2 Sigma [47/67700]? Surface density Σ using
Mlum and R
163- 172 F10.3 Msun/pc2 e_Sigma [1/983000]? Uncertainty in Sigma
174- 181 E8.2 K/cm3 Pe [10/7.9e+8]? Pressure as defined by
Equation 13 (G1)
183- 190 E8.2 K/cm3 e_Pe [101000/9.41e+11]? Uncertainty in Pe
192- 198 F7.4 [-] logaVir [0.2/56.3]? Virial parameter as defined
by Equation 12 (avir=
(R{sgima}v2R)/GM)
200- 206 F7.4 [-] e_logaVir [0.1/80]? Uncertainty in logaVir
208- 215 E8.2 Msun MLTE [28000/77000000]? Local thermodynamic
equilibrium (LTE) mass (only for Table A3)
217- 221 F5.2 K Tex [10.84/30.41]? Excitation temperature
(only for Table A3)
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Note (1): Type of structure (Section 3.2) as follows:
0 = dendrogram trunk;
1 = dendrogram branch;
2 = quickclump clump or dendrogram leaf.
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Global notes:
Note (G1): Assuming that our observed GMCs are not dispersing, we calculated the
external pressure that is needed for them to remain bound with
Equation (3) from Elmegreen (1989ApJ...338..178E 1989ApJ...338..178E):
Pe=(3ΠM{sgima}v2k)/(4πR3)
where we adopt Π=0.5 as the ratio between the local and mean
ionized gas densities, and k is the Boltzmann constant.
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History:
From electronic version of the journal
License: CC-BY-4.0
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 27-Jul-2026