Masers as Probes of Massive Star Formation in the Nuclear Disk

Abstract

OH(1720 MHz) and methanol masers are now recognized to be excellent probes of the interactions of supernova remnants with molecular clouds and tracers of massive star formation, respectively. To better understand the nature of star formation activity in the central region of the Galaxy, we have used these two classes of masers combined with the IRAC and MIPS data to study prominent sites of ongoing star formation in the nuclear disk. The nuclear disk is characterized by massive GMCs with elevated gas temperatures, compared to their dust temperatures. We note an association between methanol masers and a class of mid-infrared ``green sources''. These highly embedded YSOs show enhanced 4.5micron emission due to excited molecular lines. The distribution of methanol masers and supernova remnants suggest a low efficiency of star formation (with the exception of Sgr B2), which we believe is due to an enhanced flux of cosmic ray electrons impacting molecular clouds in the nuclear disk. We also highlight the importance of cosmic rays in their ability to heat molecular clouds, and thus increase the gas temperature.

arXiv comment8 pages, 3 figures, IAU 242 on "Astrophysical Masers and Their Environments", editors: J. Chapman and W. Baan

References in corpus (17)

• Interpreting Spectral Energy Distributions from Young Stellar Objects. I. A grid of 200,000 YSO model SEDs
• The First Measurement of Spectral Lines in a Short-Period Star Bound to the Galaxy's Central Black Hole: A Paradox of Youth
• The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics and Formation
• Stellar dynamics in the central arcsecond of our galaxy
• A Spitzer Space Telescope Infrared Survey of Supernova Remnants in the Inner Galaxy
• Hot and Diffuse Clouds near the Galactic Center Probed by Metastable H3+
• A deep submillimetre survey of the Galactic Centre
• A $\lambda$20cm Survey of the Galactic Center Region I: Detection of Numerous Linear Filaments
• The Mouse That Soared: High Resolution X-ray Imaging of the Pulsar-Powered Bow Shock G359.23-0.82
• OH 1720 MHz Masers in Supernova Remnants --- C-Shock Indicators
• The Origin of Diffuse X-ray and $\gamma$-ray Emission from the Galactic Center Region: Cosmic Ray Particles
• Evidence for a Weak Galactic Center Magnetic Field from Diffuse Low Frequency Nonthermal Radio Emission
• Enhanced OH in C-type shock waves in molecular clouds
• High-Resolution, Wide-Field Imaging of the Galactic Center Region at 330 MHz
• Outflows from Massive YSOs as Seen with the Infrared Array Camera
• Observations of Massive Star Forming Regions with Water Masers: Mid-Infrared Imaging
• High-resolution Observations of OH(1720 MHz) Masers Toward the Galactic Center

Cited by in corpus (4)

• The 1st Fermi Lat Supernova Remnant Catalog
• Star Formation in the Central 400 pc of the Milky Way: Evidence for a Population of Massive YSOs
• A Survey of Hydroxyl Toward Supernova Remnants: Evidence for Extended 1720 MHz Maser Emission
• Star Formation Sites toward the Galactic Center Region: The Correlation of CH3OH Masers, H2O Masers, and Near-IR Green Sources