The Formation of Bulges, Discs and Two Component Galaxies in the CANDELS Survey at z < 3

Abstract

We examine a sample of 1495 galaxies in the CANDELS fields to determine the evolution of two component galaxies, including bulges and discs, within massive galaxies at the epoch 1 < z < 3 when the Hubble sequence forms. We fit all of our galaxies' light profiles with a single Sérsic fit, as well as with a combination of exponential and Sérsic profiles. The latter is done in order to describe a galaxy with an inner and an outer component, or bulge and disc component. We develop and use three classification methods (visual, F-test and the RFF) to separate our sample into 1-component galaxies (disc/spheroids-like galaxies) and 2-component galaxies (galaxies formed by an 'inner part' or bulge and an 'outer part' or disc). We then compare the results from using these three different ways to classify our galaxies. We find that the fraction of galaxies selected as 2-component galaxies increases on average 50 per cent from the lowest mass bin to the most massive galaxies, and decreases with redshift by a factor of four from z = 1 to z = 3. We find that single Sérsic 'disc-like' galaxies have the highest relative number densities at all redshifts, and that 2-component galaxies have the greatest increase and become at par with Sérsic discs by z = 1. We also find that the systems we classify as 2-component galaxies have an increase in the sizes of their outer components, or 'discs', by about a factor of three from z = 3 to z = 1.5, while the inner components or 'bulges' stay roughly the same size. This suggests that these systems are growing from the inside out, whilst the bulges or protobulges are in place early in the history of these galaxies. This is also seen to a lesser degree in the growth of single 'disc-like' galaxies vs. 'spheroid-like' galaxies over the same epoch.

MNRAS accepted

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Cited by in corpus (11)

• Galaxy And Mass Assembly (GAMA): ${\mathcal{M}}_{\star }-R_{\mathrm{e}}$ relations of $z=0$ bulges, discs and spheroids
• SDSS-IV MaNGA: Effects of Morphology in the global and local Star Formation Main Sequences
• The mass, colour, and structural evolution of today's massive galaxies since z~5
• The colors and sizes of recently quenched galaxies: a result of compact starburst before quenching
• Unbiased Differential Size Evolution and the Inside-Out Growth of Galaxies in the Deep CANDELS GOODS Fields at $1\le z\le 7$
• Disky elliptical galaxies and the allegedly over-massive black hole in the compact massive `ES' galaxy NGC 1271
• The continuous rise of bulges out of galactic disks
• Indications of the invalidity of the exponentiality of the disk within bulges of spiral galaxies
• Stellar populations, stellar masses and the formation of galaxy bulges and discs at $z<3$ in CANDELS
• Formation of disc galaxies around z~2
• The Chandra Deep Field South as a test case for Global Multi Conjugate Adaptive Optics