We investigate the co-evolution of the black hole accretion rate (BHAR) and the star formation rate (SFR) in $1.5lt zlt 2.5$ galaxies displaying a greater diversity of star-forming properties compared to previous studies. We combine X-ray stacking and far-IR photometry of stellar mass-limited samples of normal star-forming, starburst, and quiescent/quenched galaxies in the COSMOS field. We corroborate the existence of a strong correlation between BHAR (i.e., the X-ray luminosity, LX) and stellar mass (M*) for normal star-forming galaxies, though we find a steeper relation than previously reported. We find that starbursts show a factor of three enhancement in BHAR compared to normal SF galaxies (against a factor of six excess in SFR), while quiescents show a deficit of a factor times 5.5 at a given mass. One possible interpretation of this is that the starburst phase does not coincide with cosmologically relevant BH growth, or that starburst-inducing mergers are more efficient at boosting SFR than BHAR. Contrary to studies based on smaller samples, we find that the BHAR/SFR ratio of main-sequence (MS) galaxies is not mass invariant, but scales weakly as $M_{*}^{0.43pm 0.09}$, implying faster BH growth in more massive galaxies at $zsim 2$. Furthermore, BHAR/SFR during the starburst is a factor of two lower than in MS galaxies, at odds with the predictions of hydrodynamical simulations of merger galaxies that foresee a sudden enhancement of LX/SFR during the merger. Finally, we estimate that the bulk of the accretion density of the universe at $zsim 2$ is associated with normal star-forming systems, with only $sim 6(pm 1)%$ and $sim 11(pm 1)%$ associated with starburst and quiescent galaxies, respectively.
Rodighiero, G., Brusa, M., Daddi, E., Negrello, M., Mullaney, J.R., Delvecchio, I., et al. (2015). RELATIONSHIP BETWEEN STAR FORMATION RATE AND BLACK HOLE ACCRETION AT Z=2: THE DIFFERENT CONTRIBUTIONS IN QUIESCENT, NORMAL AND STARBUST GALAXIES. THE ASTROPHYSICAL JOURNAL LETTERS, 800(1), 1-5 [10.1088/2041-8205/800/1/L10].
RELATIONSHIP BETWEEN STAR FORMATION RATE AND BLACK HOLE ACCRETION AT Z=2: THE DIFFERENT CONTRIBUTIONS IN QUIESCENT, NORMAL AND STARBUST GALAXIES
BRUSA, MARCELLA;DELVECCHIO, IVAN;POZZI, FRANCESCA;CIMATTI, ANDREA;
2015
Abstract
We investigate the co-evolution of the black hole accretion rate (BHAR) and the star formation rate (SFR) in $1.5lt zlt 2.5$ galaxies displaying a greater diversity of star-forming properties compared to previous studies. We combine X-ray stacking and far-IR photometry of stellar mass-limited samples of normal star-forming, starburst, and quiescent/quenched galaxies in the COSMOS field. We corroborate the existence of a strong correlation between BHAR (i.e., the X-ray luminosity, LX) and stellar mass (M*) for normal star-forming galaxies, though we find a steeper relation than previously reported. We find that starbursts show a factor of three enhancement in BHAR compared to normal SF galaxies (against a factor of six excess in SFR), while quiescents show a deficit of a factor times 5.5 at a given mass. One possible interpretation of this is that the starburst phase does not coincide with cosmologically relevant BH growth, or that starburst-inducing mergers are more efficient at boosting SFR than BHAR. Contrary to studies based on smaller samples, we find that the BHAR/SFR ratio of main-sequence (MS) galaxies is not mass invariant, but scales weakly as $M_{*}^{0.43pm 0.09}$, implying faster BH growth in more massive galaxies at $zsim 2$. Furthermore, BHAR/SFR during the starburst is a factor of two lower than in MS galaxies, at odds with the predictions of hydrodynamical simulations of merger galaxies that foresee a sudden enhancement of LX/SFR during the merger. Finally, we estimate that the bulk of the accretion density of the universe at $zsim 2$ is associated with normal star-forming systems, with only $sim 6(pm 1)%$ and $sim 11(pm 1)%$ associated with starburst and quiescent galaxies, respectively.File | Dimensione | Formato | |
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