A methodology to select galaxies just after the quenching of star formation
Date Issued
2017
Author(s)
Abstract
We propose a new methodology aimed at finding star-forming galaxies in the phase which immediately follows the star-formation (SF) quenching, based on the use of high- to low-ionization emission line ratios. These ratios rapidly disappear after the SF halt, due to the softening of the UV ionizing radiation. We focus on [O III] λ5007/Hα and [Ne III] λ3869/[O II] λ3727, studying them with simulations obtained with the cloudy photoionization code. If a sharp quenching is assumed, we find that the two ratios are very sensitive tracers as they drop by a factor of ∼ 10 within ∼10 Myr from the interruption of the SF; instead, if a smoother and slower SF decline is assumed (I.e. an exponentially declining SF history with e-folding time τ = 200 Myr), they decrease by a factor of ∼2 within ∼80 Myr. We mitigate the ionization-metallicity degeneracy affecting our methodology using pairs of emission line ratios separately related to metallicity and ionization, adopting the [N II] λ6584/[O II] λ3727 ratio as metallicity diagnostic. Using a Sloan Digital Sky Survey galaxy sample, we identify 10 examples among the most extreme quenching candidates within the [O III] λ5007/Hα versus [N II] λ6584/[O II] λ3727 plane, characterized by low [O III] λ5007/Hα, faint [Ne III] λ3869, and by blue dust-corrected spectra and (u - r) colours, as expected if the SF quenching has occurred in the very recent past. Our results also suggest that the observed fractions of quenching candidates can be used to constrain the quenching mechanism at work and its time-scales.
Volume
469
Issue
3
Start page
3108
Issn Identifier
0035-8711
Ads BibCode
2017MNRAS.469.3108C
Rights
open.access
File(s)![Thumbnail Image]()
![Thumbnail Image]()
Loading...
Name
Citro17.pdf
Description
pdf editoriale
Size
11.29 MB
Format
Adobe PDF
Checksum (MD5)
ca71de460211ae323c882358758fbf7c
Loading...
Name
28936-Citro17_P01.pdf
Description
Miur
Size
7.85 MB
Format
Adobe PDF
Checksum (MD5)
7e01fcfdd39af123c5711dcc249c067d