First detection of HCO+ absorption in the magellanic system

We present the first detection of HCO+ absorption in the Magellanic System. Using the ATCA, we observed nine extragalactic radio continuum sources behind the Magellanic System and detected HCO+ absorption toward one source located behind the leading edge of the Magellanic Bridge. The detection is located at an LSR velocity of v 214.0 0.4 km s = -1 , with an FWHM of v 4.5 1.0 km s D = -1 , and an optical depth of t (HCO ) 0.10 0.0 = 2 + . Although there is abundant neutral hydrogen (H I) surrounding the sight line in position–velocity space, at the exact location of the absorber the H I column density is low, <10 cm 20 2 - , and there is little evidence for dust or CO emission from Planck observations. While the origin and survival of molecules in such a diffuse environment remain unclear, dynamical events such as H I flows and cloud collisions in this interacting system likely play an important role

The GALFA-HI Survey: Data Release 1

We present the Galactic Arecibo L-Band Feed Array HI (GALFA-HI) survey, and its first full data release (DR1). GALFA-HI is a high resolution (~ 4'), large area (13000 deg^2), high spectral resolution (0.18 km/s), wide band (-700 < v_LSR < +700 km/s) survey of the Galactic interstellar medium in the 21-cm line hyperfine transition of neutral hydrogen conducted at Arecibo Observatory. Typical noise levels are 80 mK RMS in an integrated 1 km/s channel. GALFA-HI is a dramatic step forward in high-resolution, large-area Galactic HI surveys, and we compare GALFA-HI to past, present, and future Galactic HI surveys. We describe in detail new techniques we have developed to reduce these data in the presence of fixed pattern noise, gain variation, and inconsistent beam shapes, and we show how we have largely mitigated these effects. We present our first full data release, covering 7520 square degrees of sky and representing 3046 hours of integration time, and discuss the details of these data.Comment: Accepted to the ApJ

Cold gas outflows from the Small Magellanic Cloud traced with ASKAP

Feedback from massive stars plays a critical part in the evolution of the Universe by driving powerful outflows from galaxies that enrich the intergalactic medium and regulate star formation'. An important source of outflows may be the most numerous galaxies in the Universe: dwarf galaxies. With small gravitational potential wells, these galaxies easily lose their star-forming material in the presence of intense stellar feedback(1,2). Here, we show that a nearby dwarf galaxy-the Small Magellanic Cloud-has atomic hydrogen outflows extending at least 2 kiloparsecs from the star-forming bar of the galaxy. The outflows are cold (<400 K) and may have formed during a period of active star formation 25-60 Myr ago(3,4). The total mass of atomic gas in the outflow is about 10(7) solar masses (that is, about 3 per cent of the total atomic gas of the galaxy). The inferred mass flux in atomic gas alone, M-H1 approximate to 0.2-1.0 solar masses per year, is up to one order of magnitude greater than the star-formation rate. We suggest that most of the observed outflow will be stripped from the Small Magellanic Cloud through its interaction with its companion, the Large Magellanic Cloud, and the Milky Way, feeding the Magellanic Stream of hydrogen encircling the Milky Way.The MCELS project has been supported in part by NSF grants AST-9540747 and AST-0307613, and through the generous support of the Dean B. McLaughlin Fund at the University of Michigan—a bequest from the family of D. B. McLaughlin in memory of his lasting impact on astronomy. Parts of this research were conducted by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions, through project number CE170100013. N.M.M.-G. acknowledges funding from the Australian Research Council via grant FT150100024. We gratefully acknowledge contributions by W. Raja and K. Bannister to ASKAP commissionin