Extragalactic Absorption – The Promise of the EVLA Karl M. Menten Max-Planck-Institute for Radio Astronomy Christian Henkel (MPIfR), with 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: CH 3 OH, CN, C 2 H, HCN, HNC, HCO +, HC 3 N, CS, N 2 H +, SiO, HNCO, CH 3 CCH, CH 3 CN, SO 2, NS, NO (in addition to CO, H 2 CO, OH, H 2 O, C 3 H 2, 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

F x =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 ~ 10 4 cm -3 vs 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 5 05 – 4 04 E l = 54 K Dahmen et al pc

100 pc HNCO 5 05 – 4 04 Dahmen et al. 1997

Ott et al ATCA – Ott, Weiss, Henkel, & Walter (2005) NH 3 in NGC 253 ~ 24 GHz

The allure of absorption spectroscopy

Impellizzeri et al CH 3 OH 5 1 – 4 0 A +

CH 3 OH OH MHz Impellizzeri et al 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 CH 3 OH + 7 OH lines + …

NH 3 (3,3) GHz NH 3 (1,1) GHz NH 3 (2,2) GHz OH 2  3/2 J=9/ /26.6 GHz 23 K 64 K 123 K 511 K! Arp 220 ATCA – Ott, Henkel, Weiss, & Walter (2005)

1343 MHz 6731 MHz 4488 MHz 9423 MHz Arp 220 Salter et al Vibrationally Excited HCN

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

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 Can all be observed simultaneously with the EVLA Henkel et al Henkel et al. 1986

Methanimine CH 2 NH 1 10 – MHz Arp 220 Salter et al 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 (>10 6 cm -3 ) compact (a few thousand AU) 10 4 – 10 5 L  The 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 GHzPatnaik et al Subrahmanyan et al VLA 15 GHz B PKS 1830–211

B Wiklind & Combes 1995 (from HI absorption, Carilli et al. 1993)

HST ACS F814W York et al B-image 70 mas from galaxy center (~500 pc) A-image 330 mas from galaxy center (~2.3 kpc) B Similar picture in PKS 1830–211

CASTLES Menten et al (VLA) PKS

VLA: Menten, Carilli, & Reid 1999 PKS 1830–211 z = 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 NH 3 Metastable levels (J = K) The versatile ammonia molecule – molecular cloud thermometer

NH 3 toward B |  /  | < Murphy, Flambaum, Muller, & Henkel 2008

15.17 GHz GHz E = 23 K E = 1036 K NH 3 toward PKS 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

NH 3 T kin ~ 70 K for 80-90% of the ammonia column T kin > 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 Experiment APEX - The Atacama Pathfinder Experiment

H2OH2O NH 3 APEX Observations of the Ortho-Ground State Lines of H 2 O and NH 3 Menten et al Comparison of redshifts of NH 3 inversion lines and NH 3 rotation line will yield excellent limit on  / 

CASTLES CfA-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 BUT: Will not improve on present VLA for 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