On the influence of environment on star-forming galaxies

Transcription

1 On the influence of environment on star-forming galaxies Lizhi Xie 谢利智 Tianjin Normal University; INAF-OATS Collaborators: G. De Lucia; F. Fontanot; D. Wilman; M. Fossati

2 Galaxy properties correlate with their environment Galaxies in dense region compared to those in lowdense field are: quiescent: redder; lower SFR; Dressler 2002; Poggianti 1999; Peng 2010; less gas: HI-deficient; Giovanelli & Haynes 1985; truncated HI/CO/dust/Ha profiles; Cayatte 1990; Boselli 2014; Cortese 2010; Kenny 2004

3 Galaxy property correlates with host halo assembly history Central galaxy gas-poor galaxies, halo assemble at early time, form most stars at early time, acquire most of their angular momentum at early time, gas-poor gas-rich log M*~[9.6,10.2] Zoldan et al. 2018

4 How to distinguish the nature/nurture effect? accretion z=0 Central Central Central satellite assembly history environmental effects

5 How to distinguish the nature/nurture effect? accretion z=0 Central Central Central satellite Select central and satellite in same environment at accretion time

6 Semi-analytic model GAEA Dark Matter merger tree + Sub-grid physics = galaxy evolution history GAEA reproduces the galaxy stellar mass function at redshfit 0<z<3, as well as the measured galaxy stellar mass - gas metallicity relation from z=0 up to z~0.7. Predictions for other scaling relations including HI - stellar mass, H2 - stellar mass, stellar size - stellar mass, and SFR size - stellar mass are also i n g o o d a g r e e m e n t w i t h observations. De Lucia et al. 2015; Hirschmann et al. 2016; Xie et al SAM STRENGTH: self-consistent, computational efficient. APPLICATION: analyse galaxies statistically on cosmological scale, connect the galaxy evolution with large scale environment, test hypothetical theories, etc. hot gas re-incorporation Infall SN outflow ejected gas star cooling recycling SN, AGN reheating radio mode star formation cold gas quasar mode black hole

7 Model recipes Xie et al Multi-phase cold gas Cold Gas Stars SF law: Blitz & Rosolowsky 2006 Partition cold gas into HI and H 2 Form stars from H 2 Environmental effects on satellites A galaxy lose its hot gas reservoir once it is accreted. The removal of cold gas is not included.

8 Model HI vs. observations H2 SFR

9 Selection of model galaxies Selection: star forming satellite galaxies and central galaxies in similar environments z=0 log SFR > SFR_MS -1 dex accretion satellite satellite progenitor Central Central progenitor

10 Difference between central and satellite cen-sat HI H2 SFR Model Observation ~0.2 ~0.1 ~0.2

11 Differences between central and satellite galaxies 0.3 dex 0.5 dex 0.5 dex The difference between central galaxies and their satellite counterparts at accretion time and z=0.

12 Inconsistency between model and observation Satellite galaxies in the model deplete H2 more efficiently than HI Median evolution of satellites in cluster haloes from the model of Xie et al Preliminary results

13 Inconsistency between model and observation Satellite galaxies deplete H2 more efficiently than HI possible solution > ram-pressure stripping Considering the ram-pressure stripping of cold gas for satellite galaxies: Preliminary results

14 How the environment affect disc sizes Theoretical deduction: Removal of hot gas => no cooling gas => cold gas density decrease at all radii => gas size not change => star-forming radii might slowly decrease ram-pressure stripping of cold gas => remove gas from the disk edge => smaller HI disk radii => smaller SF radii

15 How the environment affect disc sizes Cortese et al Cortese et al SFR size/ stellar size ratio correlates with HI deficiency. HI-deficient galaxies have smaller SF size.

16 model prediction vs. observation size half SF radii, half stellar mass radii half light radii of Ha and r-band

17 Differences between central and satellite galaxies size 0.1 dex

18 Conclusion Including only strangulation, our model reproduces well the median observed HI mass, SF radii, and stellar radii for both central and satellite main sequence galaxies. For HI, SF size and stellar size, the model predicted differences between central and satellite galaxies are 0.2 dex, 0.1 dex, and 0, consistent with observational data. While for H2 and SFR, the model predictions are significantly larger than data. The over-predicted depletion of H2 could be solved by implementing a proper treatment of ram-pressure stripping of cold gas.

19 Questions It is improtant to consider removal of cold gas in a model to reproduce the gas proeprities for satellite galaxies. 1, How strong the ram-pressure stripping is? 2, What is the time-scale? tail? truncated profile? 3, When gas is removel from satellite, and the gas is consumed in star formation, what mechanism can keep enough molecular gas in the galaxy center?

20 Selection bias? Size correlates with DM halo assembly history; (figure) Gas fraction correlates with DM halo assembly history HI ratio depends on gas density;

21 How these mechanisms affect disc sizes Perspective from the model: Cold gas disc size is affected by cooling, recycling, feedback, and mergers The stellar disc size is affected by star formation, recycling, disk instability and mergers