Connecting Warm H - PowerPoint Presentation

Slide1

Connecting Warm H

2 Emission and Active Transformation within Compact Groups

Image Credit: NASA,ESA and the Hubble SM4 ERO Team

Michelle Cluver mcluver@aao.gov.auSlide2

Collaborators

Philip Appleton (NHSC/Caltech)Patrick Ogle (SSC/Caltech)Jesper Rasmussen (Dark Cosmology Centre, Copenhagen)Thomas Jarrett (IPAC/Caltech)

Ute Lisenfeld (Universidad de Granada)Pierre Guillard (SSC/Caltech)

Francois Boulanger (IAS, Orsay)Kevin Xu (NHSC/Caltech)Min Yun (UMass-Amherst)

Lourdes Verdes-Montenegro (IAA, Granada)

Thodoris

Bitsakis (U. Crete)Vassilis Charmandaris (U. Crete)Slide3

Galaxy Evolution

How do galaxies move from the blue sequence to the red cloud?What are the characteristics of galaxies with intermediate colours and what role does environment play?

Credit: T.

GonclavesSlide4

How do Galaxies Transform?

Schiminovich et al. (2007)Slide5

Transformation within Group Environments

S0 evolution significantly more dramatic in groups than in clusters (Wilman et al. 2009; Just et al. 2010); ram pressure stripping not dominant mechanism

Recent simulations show spirals in group environments strongly influenced by repetitive slow encounters, increasing mass of bulges and transforming into S0’s. 10-30% of stars and gas stripped during this process (Bekki and Couch 2011)Slide6

Shapley

supercluster (Haines et al. 2011) quenching in S0/a before they reach dense core  late-types are being transformed; quenching occurs before and after transformation to lenticularHI-deficient, disturbed with inefficient ram-pressure stripping seen in NGC 2563 group (Rasmussen et al. 2012) and Pegasus I

cluster(Rose et al. 2010)Slide7

Why Compact Groups?

Evolution is aggressive, but not too muchCompact Groups are high density environments, galaxies are strongly interacting

Relatively shallow gravitational potential well prolongs gravitational interactions (probe evolution in dense environment)Slide8

Transformation in Compact Groups

Hickson Compact Groups (

HCGs);

Hickson et al. (1982), 4+ members, median z ~ 0.03, median σ

~ 200 km/

s

Galaxies are HI deficient:

tidal interactions and ISM stripping lead to gas-poor systems (Verdes-Montenegro et al. 2001)

Negligible ram-pressure stripping from hot, tenuous medium:

in most HI-deficient groups, diffuse X-rays detected in only 50%, insufficient to remove gas significantly

Galaxies appear to be undergoing rapid evolution onto the red sequence

(Johnson et al. 2007, Walker et al. 2010)Slide9

(also Walker et al. 2012 – 174 galaxies in 37

HCGs)Only similar in distribution to Coma Infall region

Bimodality of dusty/gas-rich and dust-free/gas-poor; suggests rapid evolution

Spitzer

IRAC

colours

show tight trend correlating with evolutionary stageJohnson et al. (2007), Walker et al. (2010)

42 galaxies in 12

HCGs

Transformation in Compact GroupsSlide10

Warm Molecular Hydrogen Emission

Mid-IR emission from pure rotational H2

direct detection of H2

associated with starbursts, (U)LIRGs, AGN Genzel et al. 1998; Rigopoulou et al. 2002; Lutz et al. 2003 Mechanisms:

Far-UV induced pumping and/or

collisional heating (PDRs associated with HII regions) hard X-rays heating regions in molecular clouds, H

2

excited through collisions

collisional

excitation due to acceleration produced by shocksSlide11

Stephan’s Quintet:

An HCG with dramatic H2 Line-Cooling

High velocity (~ 800 km/

s) collision of NGC 7318b with intragroup medium: intergalactic shock wave (~35

kpc

)

17.03μm: 0.3 - 2.1MJy/sr

Powerful, widespread shock-excited H

2

emission

(Cluver et al. 2010a)Slide12

Stephan’s Quintet:

An HCG with dramatic H2 Line-Cooling

Dominates in mid-IR

H

2

fits in gap in HI distribution : implies HI converted into hot plasma + H

2

(Cluver et al. 2010a)Slide13

Optical (CFHT/

Coelum

) + X-ray (NASA/CXC/CfA/E.O’Sullivan)Slide14

Hubble WFC3 (comp) + Spitzer S(1) H

2 (blue) Image credit: Robert Hurt, Michelle Cluver (SSC)Slide15

Origin of H

2 and X-ray emissionHigh-speed collision with a multi-phase medium creates multiple shocks (velocities)

Low density HI  hot plasma (X-rays)

Denser clumps of HI  forms H2Slow MHD shocks (5-20 km/s) excite H

2

Clouds of H

2 are heated by turbulence in the hot gas i.e. the kinetic energy of shock fuels H2 emission.

Molecular gas is continuously excited by supersonic turbulence

See model of

Guillard

et al. (2009)Slide16

Ares I-X – bow shock forms collar of water dropletsSlide17

Is Stephan’s Quintet unusual or just extreme?

Spitzer

IRS

low res spectroscopy (and photometry) of 23 HCGsIntermediate HI depletion with visible signs of tidal interaction in 2+ galaxies  dynamically activeProbe evolutionary sequence + connection of SQ

Sample covers 74 group members

HCG 40

Cluver et al. (2012, in prep)Slide18

IRAC

Colour Evolution74 galaxies in 23 groups

H2 enhanced (above star formation) -- 13

Star Forming

Early TypesSlide19

Molecular Hydrogen Emission Galaxies (

MOHEGs) defined using H2 divided by star formation indicator (Ogle et al. 2010)

9/13 are S0 (pec

) type, 2 Sab (pec), 1 SmSlide20

HCG 57A (

Sb)– Disk spectrumSlide21

H

2 Relative to Warm Dust Emission (24mm)

Trend confirms H2/PAH result and indicates limited AGN contaminationSlide22

What is exciting H2

?Star formation – ruled outX-rays – ruled outCosmic Rays – ruled outShocks

What produces shock excitation?AGN jets? Stochastic collisions:Accretion?

Viscous Stripping? Slide23

Recent GBT + VLA observations reveal

extended, faint emission; galaxies with largest HI deficiencies have more massive, diffuse HI component (Borthakur et al. 2010) Protracted gravitational interactions

sea of material + disrupted disks Galaxies pass through debris

stochastic heating + viscous stripping Enhanced, excited H2 could be result of shock excitation as ISM interacts with tidal material – less energetic version of what we see in Stephan’s Quintet

Death by Debris?Slide24

Specific Star Formation

H

2-enhancement occurs at intermediate/low specific star formation

IRAC colour acts as proxy for sSFR Slide25

A Green Valley Connection

In dynamically “old” groups

~40% of late-type and

~50% of early-type lie in so-called “green valley”Bitsakis et al. (2010)

In “dynamically old” groups

>70% of early-types are

S0’sSlide26

How do you make an S0?

Ram Pressure Stripping (e.g. Gunn and Gott 1972)Truncation of gas replenishment (e.g. Bekki

2002)Tidal Encounters (e.g. Icke 1985)

Minor merging (e.g. Bekki 1998)Slow encounters in groups  builds bulge mass

+

gas

stripping (Bekki and Couch 2011)Slide27

Compact Groups may be key

To what extent are galaxies pre-processed in a group environment through:

Building bulge-dominated disksIntragroup HI stripping/heatingSlide28

Group Environment

Other H

2-enhanced show similar location in mid-IR

colourInteracting pair, triple, cluster or compact group shown as hollow circles

SINGSSlide29

Intragroup

HI interacting with group galaxies could be common mechanism

Disrupted star formation/accretion could produce accelerated evolution

(seen in colour-colour plane)Similar to ESO 137-001 in Norma Cluster?

H

2

tail due to ram-pressure stripping (Sivanandam et al. 2010)Slide30

GAMA

ASKAP -- WALLABY

The tidal and dynamical processes influencing the evolution of galaxies in a group environment will likely be key to understanding the role of environment in driving the evolution of galaxies since

z > 1.

K.

BekkiSlide31

K.

BekkiSlide32

25B (Sa)

6B (

Sab

)

15D (S0) Slide33

Morphology, Activity

9/13 are S0 (pec) type, 2 Sab (pec), 1 Sm

1 SF spectrum with SF colours (68C) 1 AGN-dominated spectrum (56B)

Cluver et al. (2012)

68% HCG galaxies host AGN (Martinez et al. 2010)

BUT, low power low-luminosity LINERs or Sy2 (Coziol et al. 2004)

~3% broad-to-narrow-line AGNSlide34

Shock excitation could be from gas falling back onto galaxies

Velocity dispersion of gas/galaxies? No enhancement in SFR

(Iglesias-Paramo+ Vilchez 1999) overall relatively low (Bitsakis

et al. 2011)

Truncation of SF in early-types

(de la Rosa et al. 2007) Slide35

H

2 in the IGM

HCG 40

HCG 91Slide36

Significant Cooling Pathway!

Power in shock-driven molecular hydrogen line cooling has implications for models of galaxy mergersgas accretion onto galaxiesaccretion onto massive halos in early structure formation

starburst driven winds (outflows) SNR(U)LIRGSAGN (jet interactions with ISM)Slide37

Strong warm H

2 emission systems+/- 30% local 3CR radio galaxies have dominant MIR H2 (often coupled with weak thermal continuum) - MOHEGS. Mechanical heating driven by jet interaction with host ISM (Ogle et al. 2007, 2010)

Seen in central cluster galaxies (Egami et al. 2006, Donahue et al. 2011)Also in filaments in clusters (Johnstone

et al. 2007) – “cooling flows”Elliptical galaxies (Kaneda et al. 2008)Taffy Galaxies (Peterson et al., ApJ in press)Slide38

LVL: Dale et al. (2009) < 11

Mpc 258 galaxies (dominated by spiral and irregular) HCG: Bitsakis

et al. (2011) 135 galaxies in 32 HCGsSlide39

HCG 56

HCG 40

HCG 68

HCG 57

HCG 25

HCG 95