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Young massive stars in the ISOGAL survey. I. VLA observations of the ISOGAL l = +45 field

Testi, L. and Felli, M. and Taylor, G. B. (1999) Young massive stars in the ISOGAL survey. I. VLA observations of the ISOGAL l = +45 field. Astronomy and Astrophysics Supplement Series, 138 (1). pp. 71-85. ISSN 0365-0138. doi:10.1051/aas:1999498.

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We present VLA radio continuum observations at 3.6 and 6 cm of a ~0.65 sq. deg. field in the galactic plane at l = +45°. These observations are meant to be used in a comparison with ISO observations at 7 and 15 μm of the same region. In this paper we compare the radio results with other radio surveys and with the IRAS-PSC. At 3.6 and/or 6 cm we detect a total of 34 discrete sources, 13 of which are found in five separate extended complexes. These are all multiple or single extended thermal ultra-compact HII (UCHII) regions. While for each of these complexes an IRAS counterpart could be reliably found, no IRAS counterpart could be reliably identified for any of the remaining 21 sources. Of these 21 compact sources, six are candidate UCHII regions, and the other 15 are most probably background extragalactic non-thermal sources. The five IRAS sources associated with the radio continuum complexes all satisfy the [Wood & Churchwell (1989a]WC89; WC89) color criteria for UCHII. None of the other 38 IRAS point sources present in our surveyed field show the same colors. This fraction of WC89 type to total IRAS sources is consistent with what is found over the entire galactic plane. The fact that, when observed with a compact VLA configuration, the IRAS sources with “UCHII colors” are found to be associated with arcminute-scale extended sources, rather than with compact or unresolved radio sources, may have important implications on the estimated lifetime of UCHII regions.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Testi, L.0000-0003-1859-3070
Taylor, G. B.0000-0001-6495-7731
Additional Information:© European Southern Observatory (ESO), 1999. Received March 22; accepted May 19, 1999. Support from CNR-NATO Advanced Fellowship program and from NASA's Origins of Solar Systems program (through grant NAGW-4030) is gratefully acknowledged.
Funding AgencyGrant Number
Consiglio Nazionale delle Ricerche (CNR)UNSPECIFIED
North Atlantic Treaty Organization (NATO)UNSPECIFIED
Subject Keywords:HII regions / galaxy: stellar content / stars: early-type / stars: formation / radio continuum: ISM
Issue or Number:1
Record Number:CaltechAUTHORS:20180413-132853847
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Official Citation:Young massive stars in the ISOGAL survey - I. VLA observations of the ISOGAL Formula field L. Testi, M. Felli and G. B. Taylor Astron. Astrophys. Suppl. Ser., 138 1 (1999) 71-85 DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85839
Deposited By: George Porter
Deposited On:13 Apr 2018 20:45
Last Modified:15 Nov 2021 20:32

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