Near-infrared Spectroscopy of Ultracompact H ii Regions in W51A with NIFS/ALTAIR*

Autor(es)

Barbosa, Cassio L. ; Navarete, Felipe ; Blum, Robert D. ; Damineli, Augusto ; Conti, Peter S.

• Tipo de documento: Artigo Científico
• Fonte: ASTROPHYSICAL JOURNAL; v. 941, n. 1, p. 13-pg., 2022-12-01.

Resumo

W51A is the most active star formation region of the giant H ii region W51. It harbors the two massive protoclusters W51e and W51 IRS2, which are very rare in the Galaxy. We aim to identify the newborn massive stars and ultracompact H ii regions to derive its distance and age. We performed Integral Field Unit observations with NIFS+ALTAIR of nine targets in the W51A subregion. The distance modulus was obtained using the spectral classification in the K band and a reddening law appropriate to the inner Galactic plane. We derived the distance and the spectral types for five of the targets, ranging from O8 to O9.5, similar to those derived from radio continuum data, except for two sources to which we assigned a somewhat later spectral type. We included another seven objects with precise spectral classification from other works, which allowed us to better constrain the distance estimate. Our spectrophotometric distance d = 4.80 +/- 1.27 kpc is in good agreement with those derived from the Galactic rotation model and trigonometric parallaxes, placing the region near the tangent point of the Sagittarius arm. We conclude that the stars studied in this work have an age spread of 1.5-4 Myr, substantially older than thought to date. (AU)

• Processo FAPESP: 18/06695-4 - Ciência e Evolução do Observatório Gemini
• Beneficiário: Cássio Leandro Dal Ri Barbosa
• Modalidade de apoio: Auxílio à Pesquisa - Reunião - Exterior
• Processo FAPESP: 11/51680-6 - Explorando o universo: da formação de galáxias aos planetas tipo-Terra, com o Telescópio Gigante Magellan
• Beneficiário: Laerte Sodré Junior
• Modalidade de apoio: Auxílio à Pesquisa - Projetos Especiais
• Processo FAPESP: 06/02467-0 - A formação de estrelas de alta massa
• Beneficiário: Cássio Leandro Dal Ri Barbosa
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores