Return to [Log-]Normalcy: Rethinking Quenching, The Star Formation Main Sequence, and Perhaps Much More

Journal
Date Issued
2016
Author(s)
Abramson, Louis E.
•
Gladders, Michael D.
•
Dressler, Alan
•
Oemler, Augustus, Jr.
•
•
DOI
Abstract
Knowledge of galaxy evolution rests on cross-sectional observations of different objects at different times. Understanding of galaxy evolution rests on longitudinal interpretations of how these data relate to individual objects moving through time. The connection between the two is often assumed to be clear, but we use a simple “physics-free” model to show that it is not and that exploring its nuances can yield new insights. Comprising nothing more than 2094 loosely constrained lognormal star formation histories (SFHs), the model faithfully reproduces the following data it was not designed to match: stellar mass functions at z≤slant 8; the slope of the star formation rate/stellar mass relation (the SFR “Main Sequence”) at z≤slant 6; the mean {sSFR}(\equiv {SFR}/{M}* ) of low-mass galaxies at z≤slant 7; “fast-” and “slow-track” quenching; downsizing; and a correlation between formation timescale and {sSFR}({M}* ,t) similar to results from simulations that provides a natural connection to bulge growth. We take these findings—which suggest that quenching is the natural downturn of all SFHs affecting galaxies at rates/times correlated with their densities—to mean that: (1) models in which galaxies are diversified on Hubble timescales by something like initial conditions rival the dominant grow-and-quench framework as good descriptions of the data; or (2) absent spatial information, many metrics of galaxy evolution are too undiscriminating—if not inherently misleading—to confirm a unique explanation. We outline future tests of our model but stress that, even if ultimately incorrect, it illustrates how exploring different paradigms can aid learning and, we hope, more detailed modeling efforts.
Volume
832
Issue
1
Start page
7
Uri
Url
Issn Identifier
0004-637X
Ads BibCode
2016ApJ...832....7A
Rights
open.access
File(s)
Loading...
Thumbnail Image
Name

Abramson_2016_ApJ_832_7.pdf

Description
PDF editoriale
Size

2.76 MB

Format

Adobe PDF

Checksum (MD5)

c85cf1d7163e43a1b0b5dd9db16ee528