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Deeply Embedded Protostellar Population in the Central Molecular Zone Suggested by H2O Masers and Dense Cores

Published online by Cambridge University Press:  09 February 2017

Xing Lu
Affiliation:
School of Astronomy and Space Science, Nanjing University, Nanjing, Jiangsu 210023, China Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
Qizhou Zhang
Affiliation:
Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
Jens Kauffmann
Affiliation:
Max Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
Thushara Pillai
Affiliation:
Max Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
Steven N. Longmore
Affiliation:
Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK
J. M. Diederik Kruijssen
Affiliation:
Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstraße 12-14, D-69120 Heidelberg, Germany
Cara Battersby
Affiliation:
Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
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Abstract

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The Central Molecular Zone (CMZ), usually referring to the inner 500 pc of the Galaxy, contains a dozen of massive (~105M) molecular clouds. Are these clouds going to actively form stars like Sgr B2? How are they affected by the extreme physical conditions in the CMZ, such as strong turbulence? Here we present a first step towards answering these questions. Using high-sensitivity, high angular resolution radio and (sub)millimeter observations, we studied deeply embedded star formation in six massive clouds in the CMZ, including the 20 and 50 km s−1 clouds, Sgr B1 off (as known as dust ridge clouds e/f), Sgr C, Sgr D, and G0.253 – 0.016. The VLA water maser observations suggest a population of deeply embedded protostellar candidates, many of which are new detections. The SMA 1.3 mm continuum observations reveal peaks in dust emission associated with the masers, suggesting the existence of dense cores. While our findings confirm that clouds such as G0.253 – 0.016 lack internal compact substructures and are quiescent in terms of star formation, two clouds (the 20 km s−1 cloud and Sgr C) stand out with clusters of water masers with associated dense cores which may suggest a population of deeply embedded protostars at early evolutionary phases. Follow-up observations with VLA and ALMA are necessary to confirm their protostellar nature.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2017 

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