TOWARD A UNIFICATION OF STAR FORMATION RATE DETERMINATIONS IN THE MILKY WAY AND OTHER GALAXIES

By L. Chomiuk, M. Povich. 2011

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The star formation rate (SFR) of the Milky Way remains poorly known, with often-quoted values ranging from 1 to 10 M☉ yr−1. This situation persists despite the potential for the Milky Way to serve as the ultimate SFR calibrator for external galaxies. We show that various estimates for the Galactic SFR are consistent with one another once they have been normalized to the same initial mass function (IMF) and massive star models, converging to 1.9 ± 0.4 M☉ yr−1. However, standard SFR diagnostics are vulnerable to systematics founded in the use of indirect observational tracers sensitive only to high-mass stars. We find that absolute SFRs measured using resolved low/intermediate-mass stellar populations in Galactic H ii regions are systematically higher by factors of ∼2–3 compared with calibrations for SFRs measured from mid-IR and radio emission. We discuss some potential explanations for this discrepancy and conclude that it could be allayed if (1) the power-law slope of the IMF for intermediate-mass (1.5 M☉ < m < 5M☉) stars were steeper than the Salpeter slope or (2) a correction factor was applied to the extragalactic 24 μm SFR calibrations to account for the duration of star formation in individual mid-IR–bright H ii regions relative to the lifetimes of O stars. Finally, we present some approaches for testing whether a Galactic SFR of ∼2 M☉ yr−1 is consistent with what we would measure if we could view the Milky Way as external observers. Using luminous radio supernova remnants and X-ray point sources, we find that the Milky Way deviates from expectations at the 1σ–3σ level, hinting that perhaps the Galactic SFR is overestimated or extragalactic SFRs need to be revised upward.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/6a14cb24030805f23355e9b73c78e70348d9e626

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Citations in the corpus

IMPROVED ESTIMATES OF THE MILKY WAY’S STELLAR MASS AND STAR FORMATION RATE FROM HIERARCHICAL BAYESIAN META-ANALYSIS (2014, methodology): “The incorporated studies use a heterogeneous mixture of assumptions and models for the Galaxy; we follow the basic model of Chomiuk & Povich (2011) and attempt to place them on a uniform basis here.”
OBSERVING THE NEXT GALACTIC SUPERNOVA (2013, methodology): “This SFR is consistent with direct estimates of the SFR, which range from 1 to 4 M yr−1 (e.g., McKee & Williams 1997; Murray & Rahman 2010; Robitaille & Whitney 2010; Chomiuk & Povich 2011; Davies et al. 2011).”
Gaseous Galaxy Halos (2012, background): “…ongoing accretion is required for galaxies at a range of redshifts (Erb, 2008; Putman et al., 2009c; Hopkins et al., 2008); the Milky Way is no exception with only ∼ 5× 109 M of fuel in the disk and a current SFR of 1-3 M /yr (Chomiuk & Povich, 2011; Smith et al., 1978; Robitaille & Whitney, 2010).”
The ATLASGAL survey: a catalog of dust condensations in the Galactic plane (2013, background): “Comparing these different tracers in a homogenous way Chomiuk & Povich (2011) arrive to an estimate of 2 M⊙ yr−1.”
A HIGHLY CONSISTENT FRAMEWORK FOR THE EVOLUTION OF THE STAR-FORMING “MAIN SEQUENCE” FROM z ∼ 0–6 (2014, result): “For additional discussion on the nature of SFR indicators and the assumptions used to derive them, see Hao et al. (2011), Murphy et al. (2011), Murphy et al. (2012), KE12.”
Star Formation in the Milky Way and Nearby Galaxies (2012, methodology): “Chomiuk & Povich (2011) have recently reviewed all methods of computing Ṁ∗ for the MW and conclude that they are consistent with Ṁ∗ = 1.9 ± 0.4 M⊙ yr −1.”
Dusty Star Forming Galaxies at High Redshift (2014, background): “These DSFGs are the most intense stellar nurseries in the Universe, and have inferred star formation rates (SFRs) of as much as a few thousand solar masses per year (compared to the MilkyWay’s paltry ∼2M⊙ yr−1 Robitaille andWhitney, 2010; Chomiuk and Povich, 2011).”
Inefficient star formation through turbulence, magnetic fields and feedback (2015, background): “For example, our entire home galaxy—the Milky Way—only produces about 2M⊙ yr −1 (Chomiuk & Povich 2011), while there is plenty of gas available to form hundreds of stars per year (Zuckerman & Palmer 1974; Zuckerman & Evans 1974).”
CHARACTERIZING THE CIRCUMGALACTIC MEDIUM OF NEARBY GALAXIES WITH HST/COS AND HST/STIS ABSORPTION-LINE SPECTROSCOPY (2012, background): “The theoretical case for a massive CGM is demonstrated by the continuing high star formation rate (SFR) in spiral galaxies (Binney & Tremaine 1987; Chomiuk & Povich 2011) as well as the detailed metallicity history in galaxies (e.g., the “G dwarf problem”; Larson 1972; Binney & Tremaine 1987;…”
The big problems in star formation: The star formation rate, stellar clustering, and the initial mass function (2014, result): “However, this method depends on uncertain estimates of the premain sequence lifetimes, and tends to give results that differ from those based on integrated light at the factor of ∼ 2 level (Chomiuk & Povich 2011; Vutisalchavakul & Evans 2013).”
The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, background): “Chomiuk & Povich (2011) present an exhaustive study across many wave bands and techniques to arrive at a global SFR ṁ for the Galaxy.”
THE STAR FORMATION RATE OF TURBULENT MAGNETIZED CLOUDS: COMPARING THEORY, SIMULATIONS, AND OBSERVATIONS (2012, background): “2, 69120 Heidelberg, Germany did, the average Galactic SFR in the Milky Way, SFRMW ≈ 1–2M yr−1 (Robitaille & Whitney 2010; Chomiuk & Povich 2011) would be about two orders of magnitude higher than the observed value (Zuckerman & Palmer 1974; Zuckerman & Evans 1974).”