Letter to the Editor

The youngest massive protostars in the Large Magellanic Cloud ^*,**

¹ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA e-mail: mmsewilo@stsci.edu
² Department of Astronomy, University of Virginia, PO Box 3818, Charlottesville, VA 22903, USA
³ Johns Hopkins University, Department of Physics and Astronomy, Homewood Campus, Baltimore, MD 21218, USA
⁴ Space Science Institute, 4750 Walnut St. Suite 205, Boulder, CO 80301, USA
⁵ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138, USA
⁶ School of Physical & Geographical Sciences, Lennard-Jones Laboratories, Keele University, Staffordshire ST5 5BG, UK
⁷ Department of Astronomy, 475 North Charter St., University of Wisconsin, Madison, WI 53706, USA
⁸ Observatories of the Carnegie Institution of Washington, 813 Santa Barbara St., Pasadena, CA, 91101 USA
⁹ CEA, Laboratoire AIM, Irfu/SAp, Orme des Merisiers, 91191 Gif-sur-Yvette, France
¹⁰ Steward Observatory, University of Arizona, 933 North Cherry Ave., Tucson, AZ 85721, USA
¹¹ Jodrell Bank Centre for Astrophysics, Alan Turing Building, School of Physics & Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK

Received: 31 March 2010
Accepted: 22 April 2010

Abstract

We demonstrate the unique capabilities of Herschel to study very young luminous extragalactic young stellar objects (YSOs) by analyzing a central strip of the Large Magellanic Cloud obtained through the HERITAGE science demonstration program. We combine PACS 100 and 160, and SPIRE 250, 350, and 500 μm photometry with 2MASS (1.25-2.17 μm) and Spitzer IRAC and MIPS (3.6-70 μm) to construct complete spectral energy distributions (SEDs) of compact sources. From these, we identify 207 candidate embedded YSOs in the observed region, ~40% never-before identified. We discuss their position in far-infrared color-magnitude space, comparing with previously studied, spectroscopically confirmed YSOs and maser emission. All have red colors indicating massive cool envelopes and great youth. We analyze four example YSOs, determining their physical properties by fitting their SEDs with radiative transfer models. Fitting full SEDs including the Herschel data requires us to increase the size and mass of envelopes included in the models. This implies higher accretion rates (≳10^-4 yr^-1), in agreement with previous outflow studies of high-mass protostars. Our results show that Herschel provides reliable longwave SEDs of large samples of high-mass YSOs; discovers the youngest YSOs whose SEDs peak in Herschel bands; and constrains the physical properties and evolutionary stages of YSOs more precisely than was previously possible.