Uncovering the Beast: Discovery of Embedded Massive Stellar Clusters in W49A

Author(s)

J. Alves, N. Homeier

Abstract

We present subarcsecond J, H, and Ks images (FWHM~0.5") of an

unbiased 5'×5' (16×16 pc) survey of

the densest region of the W49 giant molecular cloud. The observations

reveal four massive stellar clusters (with stars as massive as ~120

Msolar), the largest (cluster 1) about 3 pc east of the

well-known Welch ring of ultracompact H II regions. Cluster 1 is (i)

extincted by at least AV>20 mag of foreground (unrelated

and local) extinction, (ii) has more than 30 mag of internal

inhomogeneous extinction, implying that it is still deeply buried in its

parental molecular cloud, and (iii) is powering a 6 pc diameter giant H

II region seen at both the near-infrared and the radio continuum. We

also identify the exciting sources of several ultracompact H II regions.

The census of massive stars in W49A agrees or is slightly overabundant

when compared with the number of Lyman continuum photons derived from

radio observations. We argue that although the formation of the Welch

ring could have been triggered by cluster 1, the entire W49A starburst

region seems to have been multiseeded instead of resulting from a

coherent trigger.

Based on observations collected at the European Southern Observatory, La

Silla, Chile.

Organisation(s)

Department of Astrophysics

External organisation(s)

European Southern Observatory (Germany)

Journal

The Astrophysical journal Letters

Volume

589

Pages

L45-L49

ISSN

2041-8205

DOI

https://doi.org/10.1086/375801

Publication date

05-2003

Peer reviewed

Yes

Keywords

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