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 (26)

• Astropy: A Community Python Package for Astronomy
• On the variation of the Initial Mass Function
• Dust Grain Size Distributions and Extinction in the Milky Way, LMC, and SMC
• Interstellar Dust Grains
• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• The Spitzer c2d Legacy Results: Star Formation Rates and Efficiencies; Evolution and Lifetimes
• GLIMPSE: I. A SIRTF Legacy Project to Map the Inner Galaxy
• Interpreting Spectral Energy Distributions from Young Stellar Objects. II. Fitting observed SEDs using a large grid of pre-computed models
• Interpreting Spectral Energy Distributions from Young Stellar Objects. I. A grid of 200,000 YSO model SEDs
• The UKIRT Infrared Deep Sky Survey ZYJHK Photometric System: Passbands and Synthetic Colours
• Hi-GAL: the Herschel infrared Galactic Plane Survey
• The UKIDSS Galactic Plane Survey
• Common-Resolution Convolution Kernels for Space- and Ground-Based Telescopes
• A 100-parsec elliptical and twisted ring of cold and dense molecular clouds revealed by Herschel around the Galactic Center
• Variations in the Galactic star formation rate and density thresholds for star formation
• Toward a Unification of Star Formation Rate Determinations in the Milky Way and Other Galaxies
• The present-day star formation rate of the Milky-Way determined from Spitzer detected young stellar objects
• HYPERION: An open-source parallelized three-dimensional dust continuum radiative transfer code
• Star Formation in the Central 400 pc of the Milky Way: Evidence for a Population of Massive YSOs
• Rotation Curve and Mass Distribution in the Galactic Center --- From Black Hole to Entire Galaxy ---
• Three-Dimensional Radiation Transfer in Young Stellar Objects
• Infrared Diffuse Interstellar Bands in the Galactic Centre Region
• 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
• Massive Young Stellar Objects in the Galactic Center. I. Spectroscopic Identification from Spitzer/IRS Observations
• A Catalog of 24um Sources Toward the Galactic Center

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• Star formation rates and efficiencies in the Galactic Centre
• A Dynamical Model for the Formation of Gas Rings and Episodic Starbursts Near Galactic Centres
• The Galactic Center Molecular Cloud Survey. I. A Steep Linewidth-Size Relation & Suppression of Star Formation
• A modular set of synthetic spectral energy distributions for young stellar objects
• A Dynamical Model for Gas Flows, Star Formation, and Nuclear Winds in Galactic Centres
• 'The Brick' is not a brick: A comprehensive study of the structure and dynamics of the Central Molecular Zone cloud G0.253+0.016
• On the duration of the embedded phase of star formation
• Strong Evidence that the Galactic Bulge is Shining in Gamma Rays
• Effects of Gas on Formation and Evolution of Stellar Bars and Nuclear Rings in Disk Galaxies
• The Star Formation Rate of the Milky Way as seen by Herschel
• CMZoom: Survey Overview and First Data Release
• The Dense Gas Fraction in Galactic Center Clouds
• Comparing simulations of ionisation triggered star formation and observations in RCW 120
• A Census of Early Phase High-Mass Star Formation in the Central Molecular Zone
• PHANGS-JWST First Results: Duration of the early phase of massive star formation in NGC628
• Synthetic observations of star formation and the interstellar medium
• TRUST I: A 3D externally illuminated slab benchmark for dust radiative transfer
• Multi-scale Magnetic Fields in the Central Molecular Zone: Inference from the Gradient Technique
• Possible connection between the asymmetry of North Polar Spur and Loop I with Fermi Bubbles
• CMZoom II: Catalog of Compact Submillimeter Dust Continuum Sources in the Milky Way's Central Molecular Zone
• Star Formation in Nuclear Rings with the TIGRESS Framework
• Signatures of Young Star Formation Activity Within Two Parsecs of Sgr A*
• Near-infrared spectroscopic observations of massive young stellar object candidates in the Central Molecular Zone
• A network of filaments detected by Herschel in the Serpens Core: A laboratory to test simulations of low-mass star formation
• 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
• Insights from Synthetic Star-forming Regions: III. Calibration of Measurement Techniques of Star-formation Rates
• Disc-halo gas outflows driven by stellar clusters as seen in multiwavelength tracers
• Star formation rates on global and cloud scales within the Galactic Centre
• Star Formation in the Galactic Center