Extragalactic Absorption – The Promise of the EVLA

Karl M. Menten Max-Planck-Institute for Radio Astronomy

with Christian Henkel (MPIfR),Christian Henkel (MPIfR), Chris Carilli (NRAO), Mark Reid (CfA) & many others

The EVLA Vision: Galaxies through Cosmic Time December 18, 2008

Extragalactic Molecules (other than CO)Since the late 1980s (mostly) Henkel & Mauersberger and their collaborators have detected a large number of molecules toward the nuclei of local galaxies• Species include:

CH3OH, CN, C2H, HCN, HNC, HCO+, HC3N, CS, N2H+, SiO, HNCO, CH3CCH, CH3CN, SO2, NS, NO (in addition to CO, H2CO, OH, H2O, C3H2, and CH)• Sources include:

NGC 253, IC 342, NGC 6946, M82, NGC 4945, NGC 6946, Maffei 2, Arp 220, Mrk 231

• mostly starbursts, some ULIRGs• For many species rare isotopes are detected• For many species multi-transition studies afford excitation analyses

Fx=160 erg cm-2 s-1

The interstellar medium in the Central Molecular Zone of our Galaxy

The Central Molecular Zone (CMZ) • huge Giant Molecular Cloud (GMC) complex:

• ~0.3º broad band around the center of our Galaxy from l = +1.9º to -1.1º.

• GMCs in CMZ have properties that are quite different from "normal" (i.e. spiral arm) clouds: they are much • denser (n ~ 104 cm-3 vs. 102 cm-3), • much warmer (60 K < T < 120 K vs. 10 – 20 K), • and much more turbulent (v ~ 10 – 20 km/s vs. a few km/s).

HNCO 505 – 404 El = 54 K Dahmen et al. 1997

300 pc

100 pc

HNCO 505 – 404 Dahmen et al. 1997

Ott et al. 2005

ATCA – Ott, Weiss, Henkel, & Walter (2005)

NH3 in NGC 253 ~ 24 GHz

The allure of absorption spectroscopy

CCL SeSS covcov 1

1 effAS

Impellizzeri et al. 2008

CH3OH 51 – 40 A+

CH3OH

OH

1667 1665 MHz

Impellizzeri et al. 2008

Hagiwara et al. 2004

Formaldehyde 6 cm line GBT Mangum, Darling, Menten, & Henkel 2008

EVLA: Can all be observed

simultaneously with the 6.7

GHz CH3OH + 7 OH lines + …

NH3(3,3)23870.1 GHz

NH3(1,1)23.6945 GHz

NH3(2,2)23.7226 GHz

OH 23/2J=9/223817.6/26.6 GHz

23 K

64 K123 K

511 K!Arp 220

ATCA – Ott, Henkel, Weiss, & Walter (2005)

1343 MHz

6731 MHz

4488 MHz

9423 MHz

Arp 220

Salter et al. 2008

Vibrationally Excited HCN

HCN l-type transitions (GHz) E(K)/1.44 J

448.9430 715 1 1346.7652 721 2 2693.3388 730 3 4488.4723 742 4 6731.9105 756 5 9423.3348 774 6 12562.3629 795 7 16148.5495 818 8 20181.3862 845 9 24660.3100 875 10 29584.6600 907 11 34953.7600 942 12 40766.9000 981 13 47023.2000 1022 14 53721.7150 1067 15

Thorwirth et al. 2003

l-type doublet vibrationally excited HCN lines need

• 14 m radiation for their excitation and, thus

• probe mid-IR radiation field unaccessible by other means (due to high opactity)

Cesaroni & Walmsley 1991

4765 MHz

4660 MHz

4750 MHz

6017/6030/ 6035/6049 MHz

7761 MHz

7820 MHz

Rotationally Excited OH Absorption toward Arp 200

Salter et al. 2008

Can all be observed

simultaneously with the EVLA

Henkel et al. 1987

Henkel et al. 1986

Methanimine CH2NH

110 – 111

5290 MHz

Arp 220

Salter et al. 2008

EVLA 1 10 min, 1 polz’n

Detected in Galactic center

region by Godfrey et al. (1973)

Chemical Diversity in Hot Molecular Cores

(Wyrowski et al. 1999)

Hot Cores

• hot (>150 K)

• dense (>106 cm-3)

• compact (a few thousand AU)

• 104 – 105 LThe starburst region

inside Arp 220

resembles one

gigantic hot core

Intermediate Redshift Molecular Absorption

Toward Radio-loud (and preferably mm-loud)

• “Red” QSOs

• Gravitational lens systems

MERLIN 5 GHz Patnaik et al. 1993Subrahmanyan et al. 1990

VLA 15 GHz

B0218+357 PKS 1830–211

B0218+357

Wiklind & Combes 199568466.0z(from HI absorption, Carilli et al. 1993)

HST ACS F814W

York et al. 2005

B-image 70 mas from galaxy center (~500 pc) A-image 330 mas from galaxy center (~2.3 kpc)

B0218+357

Similar picture in PKS 1830–211

CASTLES

Menten et al. 1999 (VLA)

PKS 1830-211

88582.0z

VLA: Menten, Carilli, & Reid 1999

PKS 1830–211 z = 0.88582

• So far (mostly) Q-band

• Note the abyssmal spectral resolution

• Very many lines can be observed

simultaneously with the EVLA in all its

frequency bands

Energy level diagram

NH3

Metastable levels (J = K)

The versatile ammonia molecule – molecular cloud thermometer

R rot

R46.4 inv

ep mm /

NH3 toward B0218+357

|/| < 1.8 10-6

Murphy, Flambaum, Muller, & Henkel 2008

15.17 GHz

12.56 GHz E = 23 K

E = 1036 K

NH3 toward PKS 1830-211

Henkel, Braatz, Menten, & Ott 2008

Can all be observed

simultaneously with the EVLA

Background continuum between 6.5 and 8 Jy

Apparent optical depths between 0.03 and 0.0008

NH3

Tkin ~ 70 K for 80-90% of the ammonia column

Tkin> 600 K for the remaining 10-20%

Weird! This is supposed to

be a normal molecular cloud

in a random spiral arm location!

APEX - The Atacama Pathfinder ExperimentAPEX - The Atacama Pathfinder Experiment

APEX - The Atacama Pathfinder ExperimentAPEX - The Atacama Pathfinder Experiment

H2O

NH3

APEX Observations of the Ortho-Ground State Lines of H2O and NH3

Menten et al. 2008

Comparison of redshifts of NH3 inversion

lines and NH3 rotation line will yield

excellent limit on /

CASTLESCfA-Arizona Space Telescope LEns Survey of gravitational lenses

The EVLA’s improved continuum sensitivity

will allow self calibration on weak sources

and, thus, allow long integrations.

This, combined with the wide

bandwidths/many channels, will make blind

searches for redshifted absorption feasible.

Covering the whole redshift range with the EVLA

Current Frequency Coverage

Additional EVLA Coverage

©Rick Perley@NRAO

BUT: Will not improve on

present VLA for < 1 GHz,

i.e, z > 0.6 for OH lines

Low frequency capability

Multi molecule/multi transition observations with the EVLA will

• probe the hot, dense molecular gas in (even the most extreme) starburst environments

• allow fascinating studies of the (alien) interstellar media of normal, gas-rich distant galaxies, incl. magnetic field strength measurements

• provide ever more stringent limits on the evolution of fundamental constants over cosmic history

Thanks for your attention