ProFit: Bayesian profile fitting of galaxy images

Monthly Notices of the Royal Astronomical Society

et al. 2020

We use our catalogue of structural decomposition measurements for the extended GALEX Arecibo SDSS Survey (xGASS) to study the role of bulges both along and across the galaxy star-forming main sequence (SFMS). We show that the slope in the sSF R-M relation flattens by ∼0.1 dex per decade in M when re-normalising sSF R by disc stellar mass instead of total stellar mass. However, recasting the sSF R-M relation into the framework of only disc-specific quantities shows that a residual trend remains against disc stellar mass with equivalent slope and comparable scatter to that of the total galaxy relation. This suggests that the residual declining slope of the SFMS is intrinsic to the disc components of galaxies. We further investigate the distribution of bulge-to-total ratios (B/T) as a function of distance from the SFMS (∆SF R M S ). At all stellar masses, the average B/T of local galaxies decreases monotonically with increasing ∆SF R M S . Contrary to previous works, we find that the upper-envelope of the SFMS is not dominated by objects with a significant bulge component. This rules out a scenario in which, in the local Universe, objects with increased star formation activity are simultaneously experiencing a significant bulge growth. We suggest that much of the discrepancies between different works studying the role of bulges originates from differences in the methodology of structurally decomposing galaxies.

Section: Sample and Summary Of Datamentioning

confidence: 99%

xGASS: the role of bulges along and across the local star-forming main sequence

Monthly Notices of the Royal Astronomical Society

et al. 2020

“…Lastly, to isolate disk-dominated galaxies we take advantage of the bulge-to-disk decomposition of xGASS galaxies recently presented by Cook et al (2019). This has been derived from g, r and i SDSS imaging data using the Bayesian code ProFIT (Robotham et al 2017). Stellar mass bulge-to-total (B/T) ratios are then determined from the rband profile and the g − i color gradients using the empirical recipes presented in Zibetti et al (2009).…”

Section: Datamentioning

confidence: 99%

xGASS: passive discs do not host unexpectedly large reservoirs of cold atomic hydrogen

Monthly Notices of the Royal Astronomical Society: Letters

et al. 2020

We use the extended GALEX Arecibo SDSS Survey (xGASS) to quantify the relationship between atomic hydrogen (Hi) reservoir and current star formation rate (SFR) for central disk galaxies. This is primarily motivated by recent claims for the existence, in this sample, of a large population of passive disks harbouring Hi reservoirs as large as those observed in main sequence galaxies. Across the stellar mass range 10 9

“…In this section, we describe our usage of the two-dimensional structural decomposition code ProFit 1 (Robotham et al 2017) that has been designed to robustly decompose galaxy images into their separate bulge and disc components.…”

Section: Structural Decomposition Of Galaxiesmentioning

confidence: 99%

xGASS: The impact of photometric bulges on the scatter of HI scaling relations

Monthly Notices of the Royal Astronomical Society

et al. 2019

We present a structural decomposition analysis of the galaxies in the extended GALEX Arecibo SDSS Survey (xGASS) using (gri ) images from the Sloan Digital Sky Survey. Utilising the 2D Bayesian light profile fitting code ProFit, we fit single-and double-component models taking advantage of a robust Markov chain Monte Carlo optimisation algorithm in which we assume a Sérsic profile for single-component models and a combination of a Sérsic bulge and near -exponential disc (0.5 n 1.5) for double-component models. We investigate the effect of bulges on the atomic hydrogen (H I) content in galaxies by revisiting the H I-to-stellar mass scaling relations with the bulge-to-total ratio measured in the ProFit decompositions. We show that, at both fixed total and disc stellar mass, more bulge-dominated galaxies have systematically lower H I masses, implying that bulge-dominated galaxies with large H I reservoirs are rare in the local Universe. We see similar trends when separating galaxies by a bulgeto-total ratio based either on luminosity or stellar mass, however, the trends are more evident with luminosity. Importantly, when controlling for both stellar mass and star formation rate, the separation of atomic gas content reduces to within 0.3 dex between galaxies of different bulge-to-total ratios. Our findings suggest that the presence of a photometric bulge has little effect on the global H I gas reservoirs of local galaxies.