Sub-galactic scaling relations between X-ray luminosity, star-formation rate, and stellar mass

Konstantinos Kouroumpatzakis; Andreas Zezas; Paul Sell; Konstantinos Kovlakas; Paolo Bonfini; Steven Willner; Matthew Ashby; Alexandros Maragkoudakis; Thomas Jarrett

doi:10.1093/mnras/staa1063

paper

Sub-galactic scaling relations between X-ray luminosity, star-formation rate, and stellar mass

arXiv:2004.09873 · doi:10.1093/mnras/staa1063

Abstract

X-ray luminosity ( $L_{X}$ ) originating from high-mass X-ray binaries (HMXBs) is tightly correlated with the host galaxy's star-formation rate (SFR). We explore this connection at sub-galactic scales spanning $\sim$ 7 dex in SFR and $\sim$ 8 dex in specific SFR (sSFR). There is good agreement with established relations down to $SFR ≃ 1 0^{- 3} M_{⊙} y r^{- 1}$ , below which an excess of X-ray luminosity emerges. This excess likely arises from low mass X-ray binaries. The intrinsic scatter of the $L_{X}$ -SFR relation is constant, not correlated with SFR. Different star formation indicators scale with $L_{X}$ in different ways, and we attribute the differences to the effect of star formation history. The SFR derived from H $α$ shows the tightest correlation with X-ray luminosity because H $α$ emission probes stellar populations with ages similar to HMXB formation timescales, but the H $α$ -based SFR is reliable only for $sSFR > 1 0^{- 12} M_{⊙} y r^{- 1} / M_{⊙}$ .

19 pages, 13 figures, accepted for publication in MNRAS (2020-04-19)

Sub-galactic scaling relations between X-ray luminosity, star-formation rate, and stellar mass

Abstract

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