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Register a new userALMA Detects CO(3-2) within a Super Star Cluster in NGC5253
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We present observations of CO(3-2) and $^{13}$CO(3-2) emission near the supernebula in the dwarf galaxy NGC 5253, which contains one of the best examples of a potential globular cluster in formation. The 0.3 resolution images reveal an unusual molecular cloud, Cloud D1, coincident with the radio-infrared supernebula. The ~6-pc diameter cloud has a linewidth, $Delta$ v = 21.7 km/s, that reflects only the gravitational potential of the star cluster residing within it. The corresponding virial mass is 2.5 x 10$^5$ M$_odot$. The cluster appears to have a top-heavy initial mass function, with $M_{low}$~1-2 M$_odot$. Cloud D1 is optically thin in CO(3-2) probably because the gas is hot. Molecular gas mass is very uncertain but constitutes < 35% of the dynamical mass within the cloud boundaries. In spite of the presence of an estimated ~1500-2000 O stars within the small cloud, the CO appears relatively undisturbed. We propose that Cloud D1 consists of molecular clumps or cores, possibly star-forming, orbiting with more evolved stars in the core of the giant cluster.
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We present ALMA CO(3-2) observations at 0.3 arcsec resolution of He2-10, a starburst dwarf galaxy and possible high-z galaxy analogue. The warm dense gas traced by CO(3--2) is found in clumpy filaments that are kinematically and spatially distinct. The filaments have no preferred orientation or direction; this may indicate that the galaxy is not evolving into a disk galaxy. Filaments appear to be feeding the active starburst; the velocity field in one filament suggests acceleration onto an embedded star cluster. The relative strengths of CO(3-2) and radio continuum vary strongly on decaparsec scales in the starburst. There is no CO(3--2) clump coincident with the non-thermal radio source that has been suggested to be an AGN, nor unusual kinematics. The kinematics of the molecular gas show significant activity apparently unrelated to the current starburst. The longest filament, east of the starburst, has a pronounced shear of FWHM $sim40$~kms across its $sim$50~pc width over its entire $approx 0.5$ kpc length. The cause of the shear is not clear. This filament is close in projection to a `dynamically distinct CO feature previously seen in CO(1--0). The most complex region and the most highly disturbed gas velocities are in a region 200~pc south of the starburst. The CO(3--2) emission there reveals a molecular outflow, of linewidth FWZI $sim$ 120-140 kms, requiring an energy $gtrsim 10^{53} rm~ erg/s$. There is at present {it no} candidate for the driving source of this outflow.
Feedback from AGN is thought to be key in shaping the life cycle of their host galaxies by regulating star-formation activity. Therefore, to understand the impact of AGN on star formation, it is essential to trace the molecular gas out of which stars form. In this paper we present the first systematic study of the CO properties of AGN hosts at z~2 for a sample of 27 X-ray selected AGN spanning two orders of magnitude in AGN bolometric luminosity (Lbol= 10^44.7-10^46.9 erg/s) by using ALMA Band 3 observations of the CO(3-2) transition (~1 angular resolution). To search for evidence of AGN feedback on the CO properties of the host galaxies, we compared our AGN with a sample of inactive (i.e., non-AGN) galaxies from the PHIBSS survey with similar redshift, stellar masses, and SFRs. We used the same CO transition as a consistent proxy for the gas mass for the two samples in order to avoid systematics involved when assuming conversion factors. By adopting a Bayesian approach to take upper limits into account, we analyzed CO luminosities as a function of stellar masses and SFRs, as well as the ratio LCO(3-2)/M* (proxy for the gas fraction). The two samples show statistically consistent trends in the LCO(3-2)-Lfir and LCO(3-2)-M* planes. However, there are indications that AGN feature lower CO(3-2) luminosities (0.4-0.7 dex) than inactive galaxies at the 2-3sigma level when we focus on the subset of parameters where the results are better constrained and on the distribution of the mean LCO(3-2)/M*. Therefore, even by conservatively assuming the same excitation factor r31, we would find lower molecular gas masses in AGN, and assuming higher r31 would exacerbate this difference. We interpret our result as a hint of the potential effect of AGN activity (e.g., radiation and outflows), which may be able to heat, excite, dissociate, and/or deplete the gas reservoir of the host galaxies. (abridged)
We present PHANGS-ALMA, the first survey to map CO J=2-1 line emission at ~1 ~ 100pc spatial resolution from a representative sample of 90 nearby (d<~20 Mpc) galaxies that lie on or near the z=0 main sequence of star-forming galaxies. CO line emission traces the bulk distribution of molecular gas, which is the cold, star-forming phase of the interstellar medium. At the resolution achieved by PHANGS-ALMA, each beam reaches the size of a typical individual giant molecular cloud (GMC), so that these data can be used to measure the demographics, life-cycle, and physical state of molecular clouds across the population of galaxies where the majority of stars form at z=0. This paper describes the scientific motivation and background for the survey, sample selection, global properties of the targets, ALMA observations, and characteristics of the delivered ALMA data and derived data products. As the ALMA sample serves as the parent sample for parallel surveys with VLT/MUSE, HST, AstroSat, VLA, and other facilities, we include a detailed discussion of the sample selection. We detail the estimation of galaxy mass, size, star formation rate, CO luminosity, and other properties, compare estimates using different systems and provide best-estimate integrated measurements for each target. We also report the design and execution of the ALMA observations, which combine a Cycle~5 Large Program, a series of smaller programs, and archival observations. Finally, we present the first 1 resolution atlas of CO emission from nearby galaxies and describe the properties and contents of the first PHANGS-ALMA public data release.
We report millimeter/submillimeter continuum and molecular line observations of the Galactic super star cluster RCW 38, obtained from the Atacama Large Millimeter/Submillimeter Array with a minimum angular resolution of $0.17times0.15$ ($simeq289,{rm AU}times255,{rm AU}$). The C$^{18}$O image reveal many massive condensations embedded within filamentary structures extending along the northwest-southeast direction in the center of cluster. The condensations have sizes of 0.01-0.02 pc, H$_2$ column densities of $10^{23}$-$10^{24}$ cm$^{-2}$, and H$_2$ masses of 10-130 $M_odot$. In addition, the 233-GHz continuum image reveals two dense, small millimeter-sources with radii of 460 and 200 AU (Source A and Source B). Source A is embedded within the most massive C$^{18}$O condensation, whereas no counterpart is seen for Source B. The masses of Source A and Source B are estimated as 13 and 3 $M_odot$ at the optically-thin limit, respectively. The C$^{18}$O emission shows a velocity gradient of 2 km s$^{-1}$ at the central 2000 AU of Source A, which could be interpreted as a Keplerian rotation with a central mass of a few $M_odot$ or infall motion of gas. Further, the ALMA $^{12}$CO data reveal that Source A and Source B are associated with molecular outflows exhibiting maximum velocities of $sim$30-70 km s$^{-1}$. The outflows have short dynamical timescales of $<$1000 yr and high mass outflow rates of $sim10^{-4}$-$10^{-3}$ $M_odot$ yr$^{-1}$. These observational signatures suggest an early evolutionary phase of the massive star formation in Source A and Source B.
We investigate the properties of a sample of 35 galaxies, detected with ALMA at 1.1 mm in the GOODS-ALMA field (area of 69 arcmin$^2$, resolution = 0.60, RMS $simeq$ 0.18 mJy beam$^{-1}$). Using the UV-to-radio deep multiwavelength coverage of the GOODS-South field, we fit the spectral energy distributions of these galaxies to derive their key physical properties. The galaxies detected by ALMA are among the most massive at $z$ = 2-4 (M$_{star,med}$ = 8.5$ times$ 10$^{10}$ M$_odot$) and are either starburst or located in the upper part of the galaxy star-forming main sequence. A significant portion of our galaxy population ($sim$ 40%), located at $zsim$ 2.5-3, exhibits abnormally low gas fractions. The sizes of these galaxies, measured with ALMA, are compatible with the trend between $H$-band size and stellar mass observed for $zsim2$ elliptical galaxies suggesting that they are building compact bulges. We show that there is a strong link between star formation surface density (at 1.1 mm) and gas depletion time: the more compact a galaxys star-forming region is, the shorter its lifetime will be (without gas replenishment). The identified compact sources associated with relatively short depletion timescales ($sim$100 Myr), are the ideal candidates to be the progenitors of compact elliptical galaxies at $z$ $sim$ 2.
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