Satellite Galaxies (Observation) Open Questions No answers

1. Michael Balogh Department of Physics and Astronomy University of Waterloo Satellite Galaxies (Observation)Open QuestionsNo answers

2. High-level Outstanding Questions • Why are we spending two days talking about satellite galaxies? -- PvD • (How) does galaxy formation depend on “environment”? (phenomenological question) • What are the physical processes driving satellite galaxy evolution (physical question)?

3. High-level Outstanding Questions • (How) does galaxy formation depend on “environment” • Quenched fraction depends on Mstar, Mhalo, DR. • The qualitatively holds for any reasonable proxy (?) • Is Mstar the right thing to use? Vc? Mstar/r2? (Cheung et al. 2012) Woo et al. (2013)

4. High-level Outstanding Questions • What are the physical processes driving satellite galaxy evolution • Strangulation, ram-pressure, harassment, assembly bias, tidal stripping • All certainly occur – proportion will depend on halo mass, epoch, Mstar, etc.

5. High-level Outstanding Questions • (How) does galaxy formation depend on “environment” • SFH depends on host halo mass and DR. • Older stellar populations in denser regions • What are the physical processes driving satellite galaxy evolution • Strangulation, ram-pressure, harassment, assembly bias, tidal stripping • All certainly occur – proportion will depend on halo mass, epoch, Mstar, etc. • There. The basic questions are answered. All that’s left are details.

6. High-level Outstanding Questions • Do the details matter? • Probably. • Very difficult to explain why quenching is not 100% efficient at z=0 • Maybe difficult to explain why it is equally efficient at z=1! • Could indicate a problem with fundamental understanding of SF/feedback laws Weinmann et al. (2010)

7. Outstanding Questions(Details) • What do the established correlations at z=0 look like at higher redshift? • What is the SFH of satellite galaxies? Does this depend on anything? • What role is played by dynamics, of galaxy or halo? • What other quantities are relevant: HI and molecular gas? Morphology?

8. What do the established correlations at z=0 look like at higher redshift?

9. The Local Universe Centrals Wetzel et al. (2012) Woo et al. (2013) • Note the range of fq is only 0.4-0.8 over most of the parameter space. • Is there any difference between central/satellite for the same Mstar and Mhalo?

10. z=1 clusters • GCLASS: 10 z~1 clusters from SpARCs • Deep GMOS spectroscopy: complete for M>2x1010MSun

11. z=1 clusters • GCLASS: 10 z~1 clusters from SpARCs • Deep GMOS spectroscopy: complete for M>2x1010MSun

12. z=1 groups • GEEC2 sample: X-ray groups (M~6x1013) in COSMOS • Suggestive of steep mass function for passive galaxies Mok et al. (2013)

13. Redshift evolution log(Mstar) ~ 10.5 • Quiescent fractions are high out to z=1 ICBS, zCOSMOS, GEEC/GEEC2, GCLASS Woo et al. (2013) Massive clusters (>1014) Large Groups (0.5-1 x 1014) Small groups (<5x1013) Field

14. What do the established correlations at z=0 look like at higher redshift? • We have only begun to sparsely sample the parameter space at z>0.5

15. What is the SFH of satellite galaxies? • What are the relevant timescales for “environment quenching”?

16. Ages of Quiescent galaxies • High s/n spectral analysis of Coma galaxies shows dwarf galaxies of fixed s are older near the cluster centre. • Can be matched with infall models if quenching is relatively slow (t~1Gyr) • No strong constraint on when the quenching occurred Smith et al. (2012)

17. Ages of transition galaxies: Red disks • Disks in NFPS are redder near cluster centre • Gradient can be matched with slow (t~2.5 Gyr) strangulation model if quenching initiates at large radius • A delay results in a gradient somewhat too steep Taranu et al. (2013)

18. SFR distribution Wetzel et al. (2013) • Matching detailed SFR distribution and quenched fraction simultaneously is difficult • Success here with a delay+rapid quenching model • Requires understanding the SF calibration at <0.1 Msun/year Salim et al. (2007)

19. Quiescent galaxies at z=1 • Average D4000 in GCLASS quiescent galaxies shows no dependence on environment at z=1 • Requires environment-quenching rate to evolve similarly to mass-quenching rate Muzzin et al. (2012)

20. Transition galaxies at z=1? • GEEC approach is to use colours rather than SFR • Is there a population of “green” galaxies between the two sequences? Mok et al. (2013)

21. Infall models at z=1 • High red fraction at z=1 seems to require shorter delay, consistent with (1+z)-1.5 tdelay=3Gyr tdelay=3(1+z)-1.5 Mok et al. (in prep)

22. Infall models at z=1 • Fairly short quenching timescale, t<0.25Gyr, needed to match the transition population Transition Passive Mok et al. (in prep)

23. Spectral line analysis • But Hd absorption is weak: any quenching model predicts it to be stronger quenching frosting • Requires ~10 bursts per Gyr • Makes limit on quenching timescale even tighter Mok et al. (in prep)

24. What are the relevant timescales for “environment quenching”? • I don’t know. • We can probably still do a better job at z=0, carefully measuring SFR and ages, more sophisticated modeling • Potentially a lot of constraining power in doing the same tests at z>0.5, with much more data

25. What is the role of dynamics? Galaxy or halo.

26. Galaxy dynamics • Would like to use velocity information to identify galaxy orbits. e.g. Balogh et al. (1999); Nobel et al. (2013) Oman et al. (2013)

27. Galaxy orbits Radial velocity vs position for galaxies with different infall ages. Oman et al. (2013)

28. Galaxy orbits Radial velocity vs position for galaxies with different infall ages. With projection, most of the information is lost Oman et al. (2013)

29. Group Dynamics • Do properties of the halo other than its mass matter? • From SDSS, any scatter in passive fraction appears to be small Balogh & McGee (2010)

30. Global Group dynamics • No evidence for strong dependence on group dynamical state Hou et al. (2013)

31. What are the correlations with other key quantities: HI, molecular gas, morphology?

32. Morphology • Several studies have indicated that any transformation requires bulge growth • e.g. from 116 X-ray groups (photoz membership) in COSMOS: George et al. (2013)

33. Is HI a more sensitive probe? • Gavazzi et al.: Ha imaging + ALFALFA in Virgo • Galaxies become HI deficient faster than their sSFR declines • Tracking the change in molecular and neutral gas relative to SFR could be very powerful Gavazzi et al. (2013)

34. Progress? • Important to add the cosmic time variable into the detailed z=0 correlations. • Greatest scope for advance is in SDSS-like surveys covering 0.5<z<2 • Need high spatial completeness of mass-selected samples • Requires multiobjectspectrographs on wide-field, large aperture telescopes

35. ngCFHT • Concept introduced to the CFHT community at the 2010 Users Meeting in Taipei • Followed up with workshop in March 2013, over 100 participants from Canada, France, China, Taiwan, Japan, India, Korea, Brzil, Australia, USA Create a new and expanded partnership to • replace the 3.6m telescope with a 10m-class telescope, mounted on the existing pier and within the volume of the current dome. • install a dedicated wide-field (1.5 deg2) multi-object spectrograph that can simultaneously collect spectra for more than ~3000 sources. • do this by the early 2020s and immediately begin spectroscopic surveys.

36. Existing: ngCFHT