june 4, 2015dusty2004 spitzer space telescopecen a elliptical and (other) early-type galaxies t....

April 18, 2023 Dusty2004Spitzer Space TelescopeCen A

Elliptical and (other) early-type galaxies

T. WiklindESA/STScI

April 18, 2023 Dusty2004Spitzer Space TelescopeCen A

1. Cold gas in elliptical/S0 galaxies• What we know today

2. What are the issues?• Origin of early-type galaxies?• Relation between AGN and dense gas?• Connection with cooling flows• Cold dust

3. Observations needed for progress• Herschel• ALMA

April 18, 2023 Dusty2004

The gas content of elliptical galaxies

Elliptical galaxies are gas-rich objects

Type of gas

Temp

K

Density

cm-3

Mass

Mo

Fraction

Hot 107 0.1 1010 >0.8

Warm 104 102 104 - 105 >0.5

Cool 102 102 - 103 107 - 1010 0.1 - 0.2

Dust <102 >103 105 - 107 ~0.8

April 18, 2023 Dusty2004

Cold ISM in lenticular galaxies:

Atomic hydrogen:

Molecular hydrogen:

Dust emission:

30-40% of far-infrared selected S0’s

25% of far-infrared selected S0’s

40-60% at 100m (IRAS)Optical features (?)

Main problem: no unbiased (or with biased controlled) survey hasbeen done to date.

Needed: survey with well-defined mass limitpreferably without far-infrared bias

One study has been done with a volume limited sample: S0, <20 Mpc, non-peculiar,non-Virgo Detection rate ~80% for CO emission (Welch & Sage 2003).No correlation between molecular mass and blue luminosity.

April 18, 2023 Dusty2004

Oosterloo et al. 2002

HI in dust-lane ellipticals:

Regular HI disks, extended well outside the optical boundary.Well-behaved kinematics.Long-lived features.

April 18, 2023 Dusty2004

NGC759 CO(1-0)observed with PdB(Wiklind et al. 1997)

Unresolved CO emission, implying > 109 Mo

of molecular gas gas ring with r~3” inferredand confirmed optically (B-I image)(Vlasyuk & Sil’chenko 2000)

April 18, 2023 Dusty2004

NGC759 observed with Plateau de Bure(Wiklind et al. 1997)

Unresolved CO emission, implying > 109 Mo

of molecular gas gas ring with r~3” inferredand confirmed optically (B-I image)(Vlasyuk & Sil’chenko 2000)

April 18, 2023 Dusty2004

Gas in lenticulars(Pogge & Eskridge 1998)

Molecular gas has the samedistribution as the ionized gaswhile HI can be extended.

Some lenticulars with atomicgas show no evidence of starformation (Pogge & Eskridge 1998)

April 18, 2023 Dusty2004Blue cores in early-types(de Mello et al. 2004)

GOODS/ACS I

zphot ~ 0.6

April 18, 2023 Dusty2004

GOODS/ACS I + B + WFPC2 U

Blue cores in early-types(de Mello et al. 2004)

zphot ~ 0.6

April 18, 2023 Dusty2004

The origin of elliptical galaxies

• Elliptical galaxies contain an old stellar population, necessarilyformed at high z

• Two formation scenarios:(1) monolithic collapse at early times, followed by passive evolution(2) hierarchical merging, with rather late formation epoch

• Very luminous galaxies with extreme star formation rates arefound in submm surveys at redshifts 2-3

April 18, 2023 Dusty2004

Cimatti et al. 2004

Four elliptical galaxies at z = 1.6 - 1.9Spectroscopically confirmedAges ~1-1.7 Gyr (zf ~ 3)M* ~ 1-3 1011 Mo

Too few such systems arepredicted in hierarchical models

April 18, 2023 Dusty2004

Chandra Deep Field Southincluding parts of GOODS-Sand UDF

SIMBA observation =1200mrms ~0.5 mJy/beam

Bergström et al. 2004

April 18, 2023 Dusty2004

Excellent fit:Starburst galaxy at z>7, SFR ~ 500 Mo/yr; M* ~ 1012 Mo

Age ~ 0.5 Gyr

Not so good fit:Evolved elliptical at z~3Passive evolution, no star formationAge ~ 1-2 Gyr (zf ~ 5-7)

A proto-elliptical at z>7?

Submm galaxies at high redshift :

• High star formation rates ~103 Mo/yr (or more)• Massive systems with gas masses ~1010-1011 Mo (CO observations)• If SFR sustained ~108 yrs they will form ~1011 Mo in stars

For more info:Mobasher et al. 2004

Submm galaxies could be proto-ellipticals forming througheither monolithic collapse or major merger events

April 18, 2023 Dusty2004

Images from John Hibbard’sweb pagehttp://www.cv.nrao.edu/~jhibbard/

Central 7” of NGC 7252 with HST/WFPC2Whitmore et al. 1992

April 18, 2023 Dusty2004

• About 15% of radio galaxies contain a coldISM (molecular gas+dust). Same as FIRselected E (Lima et al 2000; Leon et al. 2002)

• Both centrally concentrated and extended gasdistributions with masses from ~108 - 1010 Mo

• Despite large gas masses RG fall on theFundamental Plane

• No clear correlation with LB.

• Correlation with AGN activity? Most RG’sdo not have significant amounts of cold gas…

• Six high redshift radio galaxies have beenfound to contain molecular gas (z=0.2 - 3.8)(Papadopoulos et al. 2000; de Breuck et al 2003; Greve et al. 2004).

• HzRG may be starburst galaxies: largemolecular gas mass (1011 Mo) and highLFIR (>1012 Lo)

Radio galaxies

Low redshift High redshift

April 18, 2023 Dusty2004

• NGC1275 (Per A) contains >109 Mo of molecular gas, but unknownif connected to cooling flow or on-going merger (Lazareff et al. 1989)

• Molecular gas has recently been detected in 16+ cooling flow galaxies(Edge et al. 2001; Salome & Combes 2003, 2004)

• Molecular gas masses are 108 - 1010 Mo, too small to account for totalcooling flow deposition

• Strong correlation between moleculargas and H emission (Salome &Combes 2003)

• Less strong correlation betweenmolecular gas mass and massdeposition rates (but only thecentral part observed)

Molecular gas in cooling flow galaxies

Salome & Combes 2003

April 18, 2023 Dusty2004

• Dust emission is detected in many cooling flow (e.g. Edge et al. 1999)

• Heating by AGN or star formation?

• IRAM PdB images show extended CO(1-0) and CO(2-1) emissionin A1795. Apparently along the radio jet (Salome & Combes 2004).

Molecular gas in cooling flow galaxies contd.

Salome & Combes 2004

April 18, 2023 Dusty2004

• IRAS detected emission in ~40% of elliptical galaxies (Knapp et al. 1986)Md ~ 105 - 107 Mo, Td ~ 30K

• ISO sample of 54 early-type galaxies (39 E’s) with detection rate ~50%(Temi et al. 2004). ISO + SCUBA gives similar result (Leeuw et al. 2004)

• FIR luminosity not well correlated with optical luminosities (same as IRAS results)

• Two dust components:(1) A warm component with Td ~ 40 K(2) A cool component with Td ~ 17-20 K

• Total dust mass 10x larger than inferred from IRAS data

• With ~constant gas-to-dust mass ratio, more cold molecular gas is implied

Dust in elliptical galaxies

April 18, 2023 Dusty2004

Leeuw et al. 2002

April 18, 2023 Dusty2004

What can Herschel and ALMA do?

ALMA

Distribution and kinematics of molecular gas in ellipticals(study the structure of E potential)

- Radio galaxies: is the molecular gas Necessary for activity?

- Cooling flows: How is the gas related to the hot gas? Is it forming stars? Where does it form?

Molecular gas in ellipticals as a functionof redshift. Merger rate?(need HST/JWST for morphology)

Herschel

Complete and unbiased surveys of coldISM in ellipticals / radio galaxies

Detailed SEDs (+ long bolometers) toderive dust components/mass

Fine-structure lines to study the physicsof the cool ISM/star formation (Malhotraet al. 2000)

Occurance of hot/cold dust in cooling flowsdistribution / heating agent