Main-sequence stars masquerading as Young Stellar Objects in the central molecular zone

Abstract

In contrast to most other galaxies, star-formation rates in the Milky Way can be estimated directly from Young Stellar Objects (YSOs). In the Central Molecular Zone (CMZ) the star-formation rate calculated from the number of YSOs with 24 microns emission is up to order of magnitude higher than the value estimated from methods based on diffuse emission (such as free-free emission). Whether this effect is real or whether it indicates problems with either or both star formation rate measures is not currently known. In this paper, we investigate whether estimates based on YSOs could be heavily contaminated by more evolved objects such as main-sequence stars. We present radiative transfer models of YSOs and of main-sequence stars in a constant ambient medium which show that the main-sequence objects can indeed mimic YSOs at 24 microns. However, we show that in some cases the main-sequence models can be marginally resolved at 24 microns, whereas the YSO models are always unresolved. Based on the fraction of resolved MIPS 24 microns sources in the sample of YSOs previously used to compute the star formation rate, we estimate the fraction of misclassified "YSOs" to be at least 63%, which suggests that the star-formation rate previously determined from YSOs is likely to be at least a factor of three too high.

Accepted by ApJ, 11 pages, 9 figures

References in corpus (7)

• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• The UKIDSS Galactic Plane Survey
• The present-day star formation rate of the Milky-Way determined from Spitzer detected young stellar objects
• Star Formation in the Central 400 pc of the Milky Way: Evidence for a Population of Massive YSOs
• Point Sources from a Spitzer IRAC Survey of the Galactic Center
• A self-consistent model of Galactic stellar and dust infrared emission and the abundance of polycyclic aromatic hydrocarbons
• A Catalog of 24um Sources Toward the Galactic Center

Cited by in corpus (6)

• A modular set of synthetic spectral energy distributions for young stellar objects
• The FluxCompensator: Making Radiative Transfer Models of hydrodynamical Simulations Directly Comparable to Real Observations
• Does the SN rate explain the very high energy cosmic rays in the central 200 pc of our Galaxy?
• The Milky Way's Central Molecular Zone
• Star Formation in the Galactic Center
• Star formation rates on global and cloud scales within the Galactic Centre