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EVIDENCE FOR 1000 km s <sup>-1</sup> MOLECULAR OUTFLOWS IN THE LOCAL ULIRG POPULATION
Chung, Aeree,Yun, Min S.,Naraynan, Gopal,Heyer, Mark,Erickson, Neal R. IOP Publishing 2011 ASTROPHYSICAL JOURNAL LETTERS - Vol.732 No.1
<P>The feedback from galactic outflows is thought to play an important role in shaping the gas content, star formation history, and ultimately the stellar mass function of galaxies. Here we present evidence for massive molecular outflows associated with ultra-luminous infrared galaxies (ULIRGs) in the co-added Redshift Search Receiver (CO)-C-12 (1-0) spectrum. Our stacked spectrum of 27 ULIRGs at z = 0.043-0.11 (nu(rest) = 110-120 GHz) shows broad wings around the CO line with Delta V (FWZI) approximate to 2000 km s(-1). Its integrated line flux accounts for up to 25%+/- 5% of the total CO line luminosity. When interpreted as a massive molecular outflow wind, the associated mechanical energy can be explained by a concentrated starburst with star formation rate (SFR) >= 100 M-circle dot yr(-1), which agrees well with their SFR derived from the FIR luminosity. Using the high signal-to-noise stacked composite spectrum, we also probe (CO)-C-13 and (CN)-C-12 emission in the sample and discuss how the chemical abundance of molecular gas may vary depending on the physical conditions of the nuclear region.</P>
The H <small>i</small> environment of counter‐rotating gas hosts: gas accretion from cold gas blobs
Chung, Aeree,Bureau, Martin,van Gorkom, J. H.,Koribalski, Bä,rbel Blackwell Publishing Ltd 2012 Monthly notices of the Royal Astronomical Society Vol.422 No.2
<P><B>ABSTRACT</B></P><P>We probe the H <SMALL>i</SMALL> properties and the gas environments of three early‐type barred galaxies harbouring counter‐rotating ionized gas: NGC 128, NGC 3203 and NGC 7332. Each system has one or more optically identified galaxy at a similar or as yet unknown redshift within a 50‐kpc projected radius. Using H <SMALL>i</SMALL> synthesis imaging data, we investigate the hypothesis that the counter‐rotating gas in these galaxies has been accreted from their neighbours. In NGC 128 and NGC 3203, we find 9.6 × 10<SUP>7</SUP> and 2.3 × 10<SUP>8</SUP> M<SUB>⊙</SUB> of H <SMALL>i</SMALL>, respectively, covering almost the entire stellar bodies of dwarf companions that appear physically connected. Both the H <SMALL>i</SMALL> morphology and kinematics are suggestive of tidal interactions. In NGC 7332, we do not find any directly associated H <SMALL>i</SMALL>. Instead, NGC 7339, a neighbour of a comparable size at about 10 kpc, is found with 8.9 × 10<SUP>8</SUP> M<SUB>⊙</SUB> of H <SMALL>i</SMALL> gas. More recently in a single dish observation, however, another group discovered a large H <SMALL>i</SMALL> structure which seems to be an extension of NGC 7339’s H <SMALL>i</SMALL> disc and also covers NGC 7332. All these observations thus suggest that H <SMALL>i</SMALL> gas is being accreted in these three galaxies from their companions, which is likely responsible for the kinematically decoupled gas component present in their central region. In particular, the dynamical friction time‐scales of the nearest neighbours with H <SMALL>i</SMALL> gas of NGC 128 and NGC 3203 are comparable to their orbital time‐scales around the counter‐rotators, several ∼10<SUP>8</SUP> yr, implying that those neighbours will likely soon merge with the primary galaxies, fuelling them with gas. NGC 7332 also appears to be in the merging process with its neighbour through the common H <SMALL>i</SMALL> envelope. Besides, we find some other potential gas donors around NGC 128 and NGC 7332: two H <SMALL>i</SMALL>‐rich galaxies with <IMG src='/wiley-blackwell_img/equation/MNR_20679_mu1.gif' alt ='inline image'/> and 2.5 × 10<SUP>9</SUP> M<SUB>⊙</SUB> at a distance of ≈67 kpc from NGC 128 and two dwarf systems with <I>M</I><SUB>HI</SUB>= 3.9 × 10<SUP>7</SUP> and 7.4 × 10<SUP>7</SUP> M<SUB>⊙</SUB> at ≲100 kpc from NGC 7332. Among the seven H <SMALL>i</SMALL> features identified in this study, three of them are associated with dwarf galaxies, two of which have only been recently identified in a blind survey, while the third one is still not catalogued at optical wavelengths. Considering the incompleteness of existing studies of the faint dwarf galaxy population both in the optical and in H <SMALL>i</SMALL>, accretion from cold gas blobs, presumably gas‐rich dwarfs, is expected to occur even more frequently than what is inferred from such cases that have been observed to date.</P>
Chung, Eun Jung,Yun, Min S.,Verheijen, Marc A. W.,Chung, Aeree American Astronomical Society 2017 The Astrophysical Journal Vol.843 No.1
<P>This study investigated the properties of the molecular gas content and star formation activity of 17 Virgo spirals, 21 Ursa Major (UMa) spirals, 13 Pisces spiral galaxies, and a comparison sample of 11 field spiral galaxies with a spatially resolved gas and stellar distribution. The H I-deficient galaxies with a def(HI) > 0.4 have a similar range of CO luminosity normalized by the K-band luminosity (L-CO/L-K) like the field spirals, although their CO content can be smaller by up to a factor of 2. The CO, H I, and stellar disk diameters are closely related to each other for both cluster and field galaxies, and the relative diameters of the CO and H I disks grow monotonically and smoothly as the H I-to-stellar disk diameter ratio decreases. Cluster galaxies have a molecular gas consumption time up to 10 times shorter than that of the field comparison sample, suggesting a significant change in the molecular gas content and star formation activity among all the cluster galaxies, even when they do not show any sign of H i stripping. The strongly H I-stripped Virgo cluster galaxies show only a modestly reduced total gas consumption time, indicating that the star formation activity and gas consumption are a highly local (rather than global) phenomenon. Our finding is that the depletion of cold gas by ram-pressure stripping and/or starvation caused by preprocessing in each cluster environment makes galaxies evolve passively.</P>