HOPS + MALT90 + Hi-GAL: Probing star formation on a Galactic scale through mm molecular line and far-IR continuum Galactic plane surveys

Author(s)

Steven N. Longmore, Jill Rathborne, Nate Bastian, Joao Alves, Joana Ascenso, John Bally, Leonardo Testi, Andy Longmore, Cara Battersby, Eli Bressert, Cormac Purcell, Andrew Walsh, James Jackson, Jonathan Foster, Sergio Molinari, Stefan Meingast, A. Amorim, J. Lima, R. Marques, A. Moitinho, J. Pinhao, J. Rebordao, F. D. Santos

Abstract

With the HOPS and MALT90 Galactic plane surveys we are mapping a

significant fraction of the dense molecular gas in the Galaxy in over 20

dense-gas-tracing transitions (e.g. from H2O, NH3, HC3N, HC5N, N2H+,

HCN, HNC, HCO+, CH3CN, SiO, C2H, ...). Combining this with the far-IR

continuum emission from Hi-GAL we can derive the

physical/chemical/kinematic properties and evolutionary state of much of

the molecular gas in the Galaxy destined to form stars. I will present

results from three science projects based on this combined dataset,

namely: i) looking for variations in the star formation rate across the

Galaxy as a function of environment, in particular, comparing the CMZ

with the rest of the Galactic disk -- we find the rate of star formation

per unit mass of dense gas in the CMZ may be an order of magnitude lower

than that in the disk; ii) seeing if Galactic dense molecular clouds

follow the empirical relations observed in extragalactic systems (e.g.

the Kennicutt-Schmidt and Gao & Solomon relations) and what this

implies for interpretating the extragalactic relations; iii) searching

for molecular cloud progenitors of the most extreme (massive and dense)

stellar clusters. I will present one cloud we have studied as part of

project iii) which lies close to the Galactic center and which is

clearly extreme compared to the rest of the Galactic molecular cloud

population. With a mass of 10^5 Msun, a radius of only ~3pc and almost

no signs of star formation it appears to be the progenitor of an

Arches-like stellar cluster. As such, we speculate this molecular cloud

may be a local-universe-analogue of the initial conditions of a super

star cluster or potentially even a small globular cluster. From our

Galactic plane survey data this object appears to be unique in the

Galaxy, making it extremely important for testing massive cluster

formation models. We have been awarded 6 hours of ALMA Cycle 0 observing

time to study this object in detail and I hope to show preliminary

results from this data at the meeting.

Organisation(s)

Department of Astrophysics

External organisation(s)

Harvard-Smithsonian Center for Astrophysics, Boston University, European Southern Observatory (Germany), Commonwealth Scientific and Industrial Research Organisation (CSIRO), Excellence Cluster Universe, University of Colorado, Boulder, UK Astronomy Technology Centre, University of Exeter, University of Leeds, The University of Sydney, James Cook University, INAF - Osservatorio Astronomico di Roma, Universidade Técnica de Lisboa, Universidade de Coimbra, Universidade de Lisboa

Pages

14

Publication date

03-2012

Austrian Fields of Science 2012

103004 Astrophysics, 103003 Astronomy

Portal url

https://ucrisportal.univie.ac.at/en/publications/4d419946-bfd9-474b-8c1f-8a090b765afe