This week at Astro 3303

Transcription

1 This week at Astro 3303 HW #8-10 deal with your final project! (HW#8 is posted already) The project counts 20% of the grade and is expected to be a significant piece of work. HW#8 for next Wed: prepare a first outline. copies to both Dominik and me; print a paper copy to hand in. 2 nd 30min test is Nov 11. Covers material through TODAY! (emphasis on material since Oct 7 th but some background might have been introduced earlier) Today: Galaxy environments: evidence of interactions Quantifying large scale structure The Millennium Simulation Lambda-CDM Reading: Chapter 7

2 HW#8-10 & final project Today Wednesday HW #8 Be prepared to give a 3 minute oral report in class: what is your project about No slides

3 Morphological alteration mechanisms Gravitational mechanisms Galaxy-galaxy interactions Direct collisions Tidal encounters Mergers Galaxy-cluster interactions Harassment (multiple rapid tidal encounters) GRAVITY Galaxy-intracluster medium interactions Thermal evaporation Ram pressure sweeping INTRACLUSTER GAS

4 Evidence of environmental effects: Morphological disturbance => clear evidence As a kinematic tracer, HI is very useful! Gross features in HI can be reproduced by slow encounter of the 3 galaxies. M81/M82/NGC3077 Movie by Min Yun

5 Evidence of environmental effects: Morphological disturbance => clear evidence As a kinematic tracer, HI is very useful! M81/M82/NGC3077 Movie by Min Yun Starburst triggered in M82

6 TDG formation in Compact Groups De Mello MNRAS 426, 2441 Gemini spectra of 14 objects found in tails of HCGs Metallicities close to solar Very young ages (< 100 Myr)

7 HI deficiency Evidence of environmental effects: Virgo cluster Davies and Lewis 1973, MNRAS 165, 231 Chamaraux, Balkowski & Gerard 1980, A&A 83, 38 Early works noted differences between Virgo and field spirals and residual dependence of M HI /L on luminosity Comparative HI content relative to isolated galaxies Use linear diameter and include morphological type dependence Define deficiency as difference between the difference, on a logarithmic scale, between the observed HI mass and that expected for a "normal" galaxy of similar linear size and optical morphology. <DEF> = <log M HI (D lin,t) - log M HI,obs Haynes & Giovanelli 1984, AJ 89, 758

8 Solanes AJ 124, spiral galaxies HI deficiency measured as logarithmic difference between the HI mass of a Virgo galaxy of given linear diameter and morpholgical type and that expected for a field galaxy (Haynes & Giovanelli 1984!) HI Deficiency in Virgo Grayscale: ROSAT Contours: HI Def

9 VCC/M49 Arrigoni Battaia A&Ap 543, 112 Sancisi+ (1987) found HI cloud displaced from VCC1249 towards M49 McNamara+ (1994) showed trail of debris offset from HI gas GUViCS, NGVS and new Hα imaging Both ram-pressure stipping and tidal interaction with M49

10 VCC 2062: Strong CO High O/H Low M dyn NGC 4694/VCC 2062: a tidal dwarf Duc+ 2007, A&A 475, 187 => Tidal dwarf

11 HI deficient galaxies in center HI deficient galaxies=> truncated HI disks Tails point away from M87 VIVA: VLA Virgo HI survey Chung+ 2009, AJ 138, 1741

12 Truncated Hα disks Koopmann & Kenney 1998, ApJ 497, L75 Koopmann & Kenney 2004, ApJ 613, 866 Virgo galaxies have reduced SFR compared to the field SF disks are truncated relative to field spirals Strong correlation between HI deficiency & normalized Hα flux

13 The Millennium Simulation project: PE#15

14 The Millennium Simulation project: PE#15

15 The Millennium Simulation project: PE#15

16 Large Scale Structure

17 Different models yield different structure

18 Characterizing structure: On what scales do galaxies cluster?

19 Characterizing structure:

20 The spatial correlation function ξ(r)

21 Observations of the correlation function

22 Morphological segregation in another guise

23 Observing different populations

24 Low-cost: Angular Correlation Function

25 The Power Spectrum

26 The Initial Power Spectrum P o (k)

27 The Initial Power Spectrum

28 Do galaxies trace the dark matter: Bias

29 The bias factor

30 Simulations SCDM: simple CDM+baryons τcdm: + extra radiation OCDM: open+cdm

31 Evolution with time

32 The ΛCDM model The Concordance Model Large number of fundamentally different observations explained with same model. No other theory except the BB that can explain all these observations Nevertheless, there are some unresolved issues

33 ΛCMD & the Missing Satellite Problem Numerical simulations based on colddark matter models predict that dark matter halos hosting galaxies like the Milky Way should be surrounded by hundreds of small dark matter halos. Over the last decade, the number of known satellites of the MW has nearly doubled. But, it is still not enough. Where are the missing satellites? CDM is wrong The low mass DM halos host no baryons ( feedback, reionization)

34 Where are the dwarfs? Papastergis+ ApJ (2013) Bolshoi Are the low mass DM halos just missing baryons?

35 Ultra-faint dwarfs in the SDSS Only 11 Milky Way dwarfs known through 2004 Since 2005, SDSS has discovered: 8 new dsphs 1 dirr 3??? dsph/gcs? Belokurov et al. (2006)

36 Transition dwarfs: Phoenix + Leo T 1.6x10 5 M D = 420 kpc M HI ~ 2.8x10 5 M M/L > 50 D = 420 kpc Ryan-Weber et al Young et al Members of the LG Is Leo T a minihalo?

37 Discovering Leo P

38 Leo T and Leo P Leo T Leo P

39 Leo P: A new LG galaxy found by its gas Giovanelli+ 2013; Rhode Skillman+ 2013; McQuinn+2013 Left: EVLA-C HI contours superposed on WIYN image Right: Original ALFALFA HI spectrum, LBW spectrum and EVLA-C spectrum