Observations of the initial formation and evolution of spiral galaxies at 1 < z < 3 in the CANDELS fields. Issue 1 (28th January 2022)

• Record Type: Journal Article
• Authors: Margalef-Bentabol, Berta; Conselice, Christopher J; Haeussler, Boris; Casteels, Kevin; Lintott, Chris; Masters, Karen; Simmons, Brooke
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 511:Issue 1(2022)
• Page Start: 1502
• Page End: 1517
• Publication Date: 2022-01-28
• Subjects: galaxies: evolution -- galaxies: high redshift -- galaxies: spiral -- galaxies: structure; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac080
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Many aspects concerning the formation of spiral and disc galaxies remain unresolved, despite their discovery and detailed study over the past 150 yr. As such, we present the results of an observational search for proto-spiral galaxies and their earliest formation, including the discovery of a significant population of spiral-like and clumpy galaxies at z &gt; 1 in deep Hubble Space Telescope CANDELS imaging. We carry out a detailed analysis of this population, characterizing their number density evolution, masses, star formation rates (SFR), and sizes. Overall, we find a surprisingly high overall number density of massive $M_{*} \gt 10^{10}\, \mathrm{M}_{\odot }$ spiral-like galaxies (including clumpy spirals) at z &gt; 1 of $0.18\, {\rm per}\, \mathrm{arcmin}^{-2}$ . We measure and characterize the decline in the number of these systems at higher redshift using simulations to correct for redshift effects in identifications, finding that the true fraction of spiral-like galaxies grows at lower redshifts as ∼ (1 + z ) −1.1 . This is such that the absolute numbers of spirals increases by a factor of ∼10 between z = 2.5 and z = 0.5. We also demonstrate that these spiral-like systems have large sizes at z &gt; 2, and high SFRs, above the main-sequence, These galaxies represent a major mode of galaxy formation in the early Universe, perhaps driven by the spiral structure itself. We finally discuss the origin of these systems, including their likely formation through gas accretion and minor mergers, but conclude that major mergers are an unlikely cause.