The Ionizing Stars of the Galactic Ultra-Compact HII Region G45.45+0.06

TL;DR

This study uses near-infrared spectroscopy with adaptive optics to identify and classify the massive stars ionizing the Galactic Ultra-Compact HII region G45.45+0.06, revealing their spectral types and surrounding features.

Contribution

First near-infrared integral-field spectroscopic identification and classification of ionizing stars in G45.45+0.06, including detection of nebular lines and circumstellar features.

Findings

Identification of hot, massive O-type stars responsible for ionization.

Detection of nebular lines typically seen in planetary nebulae.

Evidence of circumstellar disks and young stellar objects.

Abstract

Using the NIFS near-infrared integral-field spectrograph behind the facility adaptive optics module, ALTAIR, on Gemini North, we have identified several massive O-type stars that are responsible for the ionization of the Galactic Ultra-Compact HII region G45.45+0.06. The sources ``m'' and ``n'' from the imaging study of Feldt et a. 1998 are classified as hot, massive O-type stars based on their K-band spectra. Other bright point sources show red and/or nebular spectra and one appears to have cool star features that we suggest are due to a young, low-mass pre-main sequence component. Still two other embedded sources (``k'' and ``o'' from Feldt et al.) exhibit CO bandhead emission that may arise in circumstellar disks which are possibly still accreting. Finally, nebular lines previously identified only in higher excitation planetary nebulae and associated with KrIII and SeIV ions are detected in G45.45+0.06.