GIANT MOLECULAR CLOUDS AND STAR FORMATION IN THE TIDAL MOLECULAR ARM OF NGC 4039

The properties of tidally induced arms provide a means to study molecular cloud formation and the subsequent star formation under environmental conditions which, in principle, are different from quasi-stationary spiral arms. We report the properties of a newly discovered molecular gas arm of likely tidal origin at the south of NGC 4039 and the overlap region in the Antennae galaxies, with a resolution of 1.″68 × 0.″85, using the Atacama Large Millimeter/submillimeter Array science verification CO(2–1) data. The arm extends 3.4 kpc (34″) and is characterized by widths of ≲200 pc (2″) and velocity widths of typically ΔV ≃ 10–20 km s−1. About 10 clumps are strung out along this structure, most of them unresolved, with average surface densities of Σgas ≃ 10–100 M☉ pc−2, and masses of (1–8)×106 M☉. These structures resemble the morphology of beads on a string, with an almost equidistant separation between the beads of about 350 pc, which may represent a characteristic separation scale for giant molecular associations. We find that the star formation efficiency at a resolution of 6″(600 pc) is in general a factor of 10 higher than in disk galaxies and other tidal arms and bridges. This arm is linked, based on the distribution and kinematics, to the base of the western spiral arm of NGC 4039, but its morphology is different to that predicted by high-resolution simulations of the Antennae galaxies.

[1]  L. Ho,et al.  TWO POPULATIONS OF MOLECULAR CLOUDS IN THE ANTENNAE GALAXIES , 2012, 1203.1327.

[2]  P. Duc,et al.  Tides in colliding galaxies , 2011, 1112.1922.

[3]  Qizhou Zhang,et al.  UNVEILING THE PHYSICAL PROPERTIES AND KINEMATICS OF MOLECULAR GAS IN THE ANTENNAE GALAXIES (NGC 4038/9) THROUGH HIGH-RESOLUTION CO (J = 3–2) OBSERVATIONS , 2011, 1110.2496.

[4]  F. Bournaud,et al.  Studying the spatially resolved Schmidt-Kennicutt law in interacting galaxies: the case of Arp 158 , 2011, 1107.0969.

[5]  L. Verdes-Montenegro,et al.  STAR FORMATION IN THE EXTENDED GASEOUS DISK OF THE ISOLATED GALAXY CIG 96 , 2011, 1107.0588.

[6]  W. Vacca,et al.  STAR CLUSTERS IN THE TIDAL TAILS OF INTERACTING GALAXIES: CLUSTER POPULATIONS ACROSS A VARIETY OF TAIL ENVIRONMENTS , 2011, 1101.5393.

[7]  S. M. Fall,et al.  DISRUPTION OF STAR CLUSTERS IN THE INTERACTING ANTENNAE GALAXIES , 2010, 1012.4465.

[8]  R. Teyssier,et al.  THE DRIVING MECHANISM OF STARBURSTS IN GALAXY MERGERS , 2010, 1006.4757.

[9]  European Southern Observatory,et al.  THE ANTENNAE GALAXIES (NGC 4038/4039) REVISITED: ADVANCED CAMERA FOR SURVEYS AND NICMOS OBSERVATIONS OF A PROTOTYPICAL MERGER , 2010, 1005.0629.

[10]  T. Naab,et al.  ONE MOMENT IN TIME—MODELING STAR FORMATION IN THE ANTENNAE , 2010, 1003.0685.

[11]  Beverly J. Smith,et al.  SPIRALS, BRIDGES, AND TAILS: A GALAXY EVOLUTION EXPLORER ULTRAVIOLET ATLAS OF INTERACTING GALAXIES , 2010 .

[12]  X. Kong,et al.  Star formation histories within the Antennae galaxies (Arp 244) , 2009, 0909.5186.

[13]  Tetsuo Hasegawa,et al.  The Atacama Compact Array (ACA) , 2009 .

[14]  B. Madore,et al.  THE STAR FORMATION EFFICIENCY IN NEARBY GALAXIES: MEASURING WHERE GAS FORMS STARS EFFECTIVELY , 2008, 0810.2556.

[15]  B. Madore,et al.  THE STAR FORMATION LAW IN NEARBY GALAXIES ON SUB-KPC SCALES , 2008, 0810.2541.

[16]  Wendy L. Freedman,et al.  A NEW DISTANCE TO THE ANTENNAE GALAXIES (NGC 4038/39) BASED ON THE TYPE Ia SUPERNOVA 2007sr , 2008, 0807.3955.

[17]  Laboratoire d'Astrophysique de Marseille,et al.  The UV-Optical Galaxy Color-Magnitude Diagram. I. Basic Properties , 2007, 0706.3938.

[18]  Cambridge,et al.  GEMINI SPECTROSCOPIC SURVEY OF YOUNG STAR CLUSTERS IN MERGING/INTERACTING GALAXIES. III. THE ANTENNAE , 2006, astro-ph/0612136.

[19]  F. Walter,et al.  Extended Star Formation and Molecular Gas in the Tidal Arms near NGC 3077 , 2006, astro-ph/0608169.

[20]  B. Milliard,et al.  The GALEX Ultraviolet Atlas of Nearby Galaxies , 2006, astro-ph/0606440.

[21]  O. University,et al.  IRAC and MIPS Observations of the Interacting Galaxies IC 2163 and NGC 2207 , 2006, astro-ph/0605524.

[22]  K. Sheth,et al.  Spitzer Space Telescope IRAC and MIPS Observations of the Interacting Galaxies IC 2163 and NGC 2207: Clumpy Emission , 2006 .

[23]  T. Sawada,et al.  The Elongations and Supersonic Motions of Molecular Clouds , 2005, astro-ph/0510201.

[24]  D. Iono,et al.  Molecular Superbubbles in the Starburst Galaxy NGC 253 , 2005, astro-ph/0509430.

[25]  Y. Sofue,et al.  The Schmidt Law at High Molecular Densities , 2005, astro-ph/0508347.

[26]  Paul S. Smith,et al.  The Multiband Imaging Photometer for Spitzer (MIPS) , 2004 .

[27]  P. Duc,et al.  Molecular and ionized gas in the tidal tail in Stephan's Quintet , 2004, astro-ph/0407473.

[28]  J. M. van der Hulst,et al.  High-Resolution H I Mapping of NGC 4038/39 (“The Antennae”) and Its Tidal Dwarf Galaxy Candidates , 2001, astro-ph/0110581.

[29]  F. Walter,et al.  Discovery of Molecular Gas in the Outflow and Tidal Arms around M82 , 2001, astro-ph/0110283.

[30]  Spain,et al.  Molecular Gas in Tidal Dwarf Galaxies: On-going Galaxy Formation , 2001, astro-ph/0402218.

[31]  Canada,et al.  High-Resolution Imaging of Molecular Gas and Dust in the Antennae (NGC 4038/39): Super Giant Molecular Complexes , 2000, astro-ph/0005208.

[32]  S. M. Fall,et al.  The Luminosity Function of Young Star Clusters in “the Antennae” Galaxies (NGC 4038/4039) , 1999, astro-ph/9907430.

[33]  D. Schlegel,et al.  Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds , 1998 .

[34]  D. Schlegel,et al.  Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds , 1997, astro-ph/9710327.

[35]  B. Whitmore,et al.  Hubble space telescope observations of young star clusters in NGC-4038/4039, 'the antennae' galaxies , 1995 .

[36]  D. Richstone,et al.  Modeling the Spatial Distribution of Star Formation in Interacting Disk Galaxies , 1993 .

[37]  T. Umemoto,et al.  Effects of magnetic fields and rotation on the fragmentation of filamentary molecular clouds : comparison of the theory with the Orion A cloud , 1993 .

[38]  B. Elmegreen,et al.  Regular strings of H II regions and superclouds in spiral galaxies: clues to the origin of cloudy structure , 1983 .

[39]  R. Kennicutt,et al.  A comparison of measured spiral arm properties with model predictions , 1982 .

[40]  B. Elmegreen,et al.  A catalog of dark globular filaments. , 1979 .

[41]  K. Rice,et al.  Protostars and Planets V , 2005 .