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Title: AN OBJECTIVE DEFINITION FOR THE MAIN SEQUENCE OF STAR-FORMING GALAXIES

The main sequence (MS) of star-forming (SF) galaxies plays a fundamental role in driving galaxy evolution and our efforts to understand it. However, different studies find significant differences in the normalization, slope, and shape of the MS. These discrepancies arise mainly from the different selection criteria adopted to isolate SF galaxies, which may include or exclude galaxies with a specific star formation rate (SFR) substantially below the MS value. To obviate this limitation of all current criteria, we propose an objective definition of the MS that does not rely at all on a pre-selection of SF galaxies. Constructing the 3D SFR–mass–number plot, the MS is then defined as the ridge line of the SF peak, as illustrated with various figures. The advantages of such a definition are manifold. If generally adopted, it will facilitate the inter-comparison of results from different groups using the same SFR and stellar mass diagnostics, or it will highlight the relative systematics of different diagnostics. All of this could help to understand MS galaxies as systems in a quasi-steady state equilibrium and would also provide a more objective criterion for identifying quenching galaxies.
Authors:
 [1] ;  [2]
  1. INAF—Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova (Italy)
  2. Cavendish Laboratory, University of Cambridge, 19 J. J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom)
Publication Date:
OSTI Identifier:
22518466
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 801; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPARATIVE EVALUATIONS; EQUILIBRIUM; GALAXIES; MAIN SEQUENCE STARS; MASS; RED SHIFT; STAR EVOLUTION; STEADY-STATE CONDITIONS