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- study z<0.5 environmental star-formation quenching
- test strangulation scenario of Maier, Kuchner, Ziegler
et al. (2016, A&A, 590, A108) using metallicity O/H of
cluster galaxies as a quenching tracer
- constrain quenching timescales by comparing the
observed fraction of star-forming galaxies as a function
of cluster-centric radius with simulations
Cluster star formation quenching probed by gas metallicity
Christian Maier1, B. L. Ziegler1, C. P. Haines2 & G. P. Smith3 Contact: [email protected] 1University of Vienna, Department of Astrophysics 2Osservatorio Astronomico Brera 3University of Birmingham
Goals
Z(M,SFR) observed vs. theory
Mass-metallicity relation (MZR) Phase-space diagram
- LoCuSS: Local Cluster Substructure Survey, Smith et
al. (2010, MNRAS, 409, 169)
- Seven selected clusters at 0.15<z<0.26
- 2700 spectroscopic members ACReS Hectospec/MMT
- [OII]λ3727, Hβ, [OIII]λ5007, Hα, [NII]λ6584 lines
- derived SFRs from extinction-corrected Hα
- derived O/Hs from emission lines with the O3N2
method used in Maier et al. (2016, A&A, 590, A108)
Observations
Quenching timescales
Slow-then-rapid quenching
Star-forming, with
O/H measured, non-
star forming galaxies
in seven LoCuSS
clusters
Mlow:
10≤log(M/Msun)<10.5
Mhigh:
10.5≤log(M/Msun)≤11
- Mlow median O/H higher at R<R200 than field & R>R200
Difference
between measured
O/Hs and expected
O/HLi13 at measured
(SFR, mass) from
bathtub model of
Lilly et al. (2013,
ApJ, 772, 119)
O/H ~ SFR/Ф * yield
If inflow Ф
decreases or stops
(strangulation),
O/H increases
Amendment of the Wetzel et al. (2013, MNRAS, 432, 336)
delayed-then-rapid scenario:
- slow quenching (strangulation) initiated when galaxies
first pass R200
- SFRs are hardly affected (slowly decline) during a “delay”
time of 1-2 Gyrs, but metallicities increase
- after the “delay” time: galaxies have travelled to more
inner and denser regions of cluster --> rapid decline in star
formation possibly intensified by ram-pressure stripping
- SSFR-mass median values (Mlow, Mhigh) similar for
star-forming field & cluster galaxies with O/H measured
- Higher metallicities of R<R200 galaxies indicate
strangulation (gas inflow stops, no dillution with
pristine gas of the ISM, higher O/H) when they pass R200
- Lower [OIII]/Hβ ratios (corresponding to higher O/Hs)
of R<R200 galaxies indicate they are in the act of being
quenched (Quai et al. 2018, MNRAS, 478, 3335)
Strangulation scenario
Observed fraction of SF galaxies vs. Millennium
simulation (curves): quenching times (delays) ~1-2Gyrs