Redshifted Extragalactic Molecular Lines

1. Redshifted Extragalactic Molecular Lines Mechanisms 1. Thermal 2. Masers 3. Dasars Science A. High Redshift B. Galaxy Evolution C. Star Formation/ISM D. Massive Black Holes E. Cosmology F. Physical Constants Jeremy Darling (CASA, University of Colorado)

2. Redshifted Molecular Lines

3. Redshifted Molecular Lines Out of reach (Existence of molecules?)

4. Redshifted Molecular Lines • z = 0.9 gravitational lens (e.g. Muller et al. 2006) • high dipole moment • expect detections in submm galaxies soon! • dense gas tracer • star formation (akin to HCN, HCO+)

5. Chengalur, deBruyn, & Narasimha 1999 Patnaik et al. 1994 Nair et al. 1993 Redshifted Molecular Lines • z = 0.7, 0.9 gravitational lenses (Henkel et al. 2005, Menten et al. in prep) • Tunneling transitions (many) • Thermometer • Constancy of me/mp (Flambaum & Kozlov 2007)

6. Ammonia (NH3): “Umbrella” Tunneling Ammonia (NH3) Symmetric top molecule Electrostatic repulsion between N and H3 plane “Umbrella” inversion possible via tunneling (for low vibration states) Each rotation ladder has inversion splitting Inversion transitions can be masers (first maser was NH3 24 GHz!) Rohlfs & Wilson 1996

7. Ammonia (NH3): “Umbrella” Tunneling Ammonia (NH3) Symmetric top molecule Electrostatic repulsion between N and H3 plane “Umbrella” inversion possible via tunneling (for low vibration states) Each rotation ladder has inversion splitting Gastrophysics Multiple inversion lines give Trot B0218+357: z = 0.67; Trot = 35 K PKS 1830-211: z = 0.89; up to (J,K) = (10,10) detected! (Menten et al in prep) (Henkel et al 2005)

8. Redshifted Molecular Lines • z = 0.66 maser(Barvanis & Antonucci 2005) • 5 mJy line • Acceleration search (disks) • HSN targets • Cosmology

9. H2O Megamasers • Associated with Type 2 nuclei • Highly beamed • NGC 4258: • - VLBI proper motions • of maser spots • - Line accelerations • Geometric distance 7.2  0.5 Mpc • (Herrnstein et al. 1999) Herrnstein et al. 1999 NGC 4258 (H2O masers can also occur in jets and outflows)

10. Redshifted Molecular Lines • No megamasers (Phillips et al 1998, Darling et al 2003) * Menten predicts broad shallow absorption akin to Galactic Center

11. Biggs et al 2001 Redshifted Molecular Lines z = 0.7,0.9 gravitational lenses (Menten & Reid 1996, Menten et al. 1999)

12. Galactic H2CO • Dark Clouds: • - “Anomalous” H2CO absorption • (e.g. Palmer et al. 1969) • - Absorption in multiple cm lines • - No radio continuum source! Barnard 227 Darling & Goldsmith (in prep) NGC 2264 Darling & Goldsmith (in prep)

13. H2CO: The DASAR L ight A mplification by S timulated E mission of R adiation Inversion: “Heating” of lines Tx >> Tkin Pumprequired: Chemical, collisional, radiative D arkness* A mplification** by S timulated A bsorption of R adiation Townes et al(1953) Anti-Inversion: “Cooling” of lines Tx < TCMB Pumprequired: Collisions with H2 *Not really dark. **Not a true amplification.

14. Galactic H2CO • Dark Clouds: • - “Anomalous” H2CO absorption • (e.g. Palmer et al. 1969) • - Absorption in multiple cm lines • - No radio continuum source! • Can H2CO be observed in other galaxies? 2. Can “anomalous” H2CO absorption be observed in galaxy-scale analogs of Dark Clouds? Barnard 227 Darling & Goldsmith (in prep) NGC 2264 Darling & Goldsmith (in prep)

15. H2CO Absorption Against the CMB

16. H2CO: The DASAR • The CMB is the ultimate illumination source: • Behind everything • Everywhere • Uniform on arcsec scales • H2CO absorption against the CMB offers an unrivaled, extinction-free, mass-limited probe of dense (star-forming) molecular gas, independent of redshift!

17. Baan, Guesten, & Haschick (1986) Extragalactic H2CO Emission in (U)LIRGs (OH Megamasers) Arp 220 III Zw 35 Absorption in starbursts (OH absorbers) NGC 520 NGC 660 Henkel & Darling (in prep)

18. Extragalactic H2CO Emission in (U)LIRGs (OH Megamasers) Arp 220 III Zw 35 Absorption in starbursts (OH absorbers) NGC 520 NGC 660 Henkel & Darling (in prep) NGC 660, 8.4 GHz Filho, Barthel, & Ho (2002)

19. 2 cm 2 cm Arp 220 6 cm 6 cm M 82 Extragalactic H2CO • So far… • All OHMs show 6 cm emission in H2CO • All OH absorbers show 6 cm absorption • H2CO 6 cm line flip at n(H2) ~ 105.6 cm-3 • A critical density threshold for OH megamasers? • (there must also be a density upper limit where inversion is quenched… n(H2) ~ 106 cm-3) H2CO Survey of Local Star-Forming Galaxies (Mangum, Darling, Menten, & Henkel, 2007)

20. Extragalactic H2CO (Mangum et al. 2007) • So far… • All OHMs show 6 cm emission in H2CO • All OH absorbers show 6 cm absorption • H2CO 6 cm line flip at n(H2) ~ 105.6 cm-3 • A critical density threshold for OH megamasers? • (there is also an upper density where 2 cm line flips… n(H2) ~ 105.8 cm-3) 2 cm (kilomaser) 6 cm OHMs

21. Extragalactic H2CO • H2CO dasar effect spans 3 orders of magnitude in density • cm line ratio is sensitive to n(H2) Darling & Zeiger

22. Extragalactic H2CO • H2CO dasar effect is insensitive to TCMB • The effect likely becomes easier to detect with increasing redshift! Darling & Zeiger

23. Biggs et al 2001 Darling & Wiklind Extragalactic H2CO Maser Emission in (U)LIRGs (OH Megamasers) Arp 220 III Zw 35 Absorption in starbursts (OH absorbers) NGC 520 NGC 660 Absorption in dense clouds B0218+357 PKS 1830-211

24. Redshifted Molecular Lines IRAS 02524+2046 z = 0.18 OH PKS 1830-211 HI z = 0.89 z = 0.26 megamaser z = 0.9 gravitational lens

25. Merging Galaxies:

26. OH Megamasers: Tracers of Major Mergers, Star Formation, and Massive Black Holes • OH  FIR and favors dusty • environments • OHMs seem to indicate massive • black holes (small sample) • OHMs seem to favor a specific • stage of merging, star formation • Sampling a specific stage of • merging •  BH binary formation rate •  long-period GW background • There are many approaches to these • problems; no single method will be • a panacea.

27. OH Megamasers: Tracers of Major Mergers, Star Formation, and Massive Black Holes (CSOs?) • OH  FIR and favors dusty • environments • OHMs seem to indicate massive • black holes (small sample) • OHMs seem to favor a specific • stage of merging, star formation • Sampling a specific stage of • merging •  BH binary formation rate •  long-period GW background • There are many approaches to these • problems; no single method will be • a panacea. OHMs GWs Begelman, Blandford & Rees 1980

28. OH Megamasers in HI Surveys OH Megamasers: Power-law LF Increasing Merger Rate Increasing Star Formation Briggs (1998): The deeper the HI survey, the more confusion with OH megamasers At z ~ 0.1 the OH line > HI line (but remains rare) At z ~ 1 there is ~ 1 OHM per deg2 Briggs (1988) 0.2 mJy 1 mJy 5 mJy 20 mJy

29. OH Megamaser Surveys:High(er) Redshift Barriers • RFI • Receivers • Rarity Boons • Half of OH megamasers are QSO-like • Current sensitivity is adequate for z ~ 1 • More merging in past

30. Submm Galaxies Detecting OH Megamasers at High Redshift

31. 13 km s-1 PKS 1413+135: OH and HI Absorption Conjugate OH satellite lines: 1612, 1720 MHz (see also Kanekar et al. 2004) Systematic offset from HI Is the offset physical? How to assess offsets?

32. Variability in OH Megamasers: Super-VLBI Resolution Multiple independent variable features with different timescales: Segregates sizescales May segregate positions  Offers sub- milliarcsecond resolution  Sensitivity is key

33. 02524+2046 • Observations: • Day-to-day (and intraday) variation • Multiple narrow variable components • 1665 MHz line varies, often (but not always) with 1667 • Components often (but not always) correspond to peaks Darling (in prep)

34. 02524+2046 Darling (in prep) • Observations: • Unprecedented matching between 1665 and 1667 MHz lines in average and variable fits, including flaring lines • Variation envelope shows proportional 1667:1665 modulation of ~20% (~30% expected for point source) • Size scales < 1 pc (0.3 milliarcsec) • Tb > 81011 K (!) • (What is line separation in sky?)

35. Variability Studies: A Super-VLBI Single Dish Telescope • Variability studies can segregate size scales and on-sky projections of OH megamaser components with super-VLBI resolution (~pc at z = 0.2). • Roughly half of luminous OMHs at z > 0.1 are variable/compact. • We have identified compact 1665 MHz emission coincident with compact 1667 MHz lines. • Observed phenomena are consistent with strong refractive ISS (and detailed tests are possible) • ISS predictions are consistent with VLBI observations • Long-term monitoring can identify small accelerations

36. Characterizing Variability • 10% modulation • 4.5 day timescale • Assuming ISS • Variable features: • < 1.2 parsec • Quiescent features: • > 4 parsec

37. Characterizing Variability • 10% modulation • 4.5 day timescale • Assuming ISS • Variable features: • < 1.2 parsec • Quiescent features: • > 4 parsec Robishaw, Heiles, & Quataert z = 0.217

38. Magnetic Fields in OH Megamasers Robishaw, Heiles, & Quataert have detected Zeeman splitting in multiple OH megamaser galaxies! Prediction: Zeeman splitting will also be observable in OH conjugate lines and OH in molecular absorption systems (detectable at arbitrary redshift).

39. Discussion Questions: High Frequency What can be done to improve 5-10 GHz sensitivity? • Has double position switching been evaluated at high frequency? • What bandwidths can be correlated? • How good are baselines across 100 MHz? 1 GHz? • The H2CO “densitometer” offers tremendous promise • H2O surveys and studies (cosmology) • NH3 tunneling lines • High redshift CS How high in frequency can Arecibo still work with the HSA? • What is the impact of strong continuum on Arecibo within the HSA? • Any hope for observations of molecular absorption systems? Is there an irreducible noise floor? • How low can we go? • Can we have certainty when observing weak lines?

40. Discussion Questions: Low Frequency Is 800 MHz feasible? • OH (megamasers, conjugate lines, absorption) at z~1 • HI absorption (intrinsic, gravitational lenses, damped Ly systems) • Changing physical constants, peak of star formation, merging, BH growth • Interferometer with GBT, possibly WSRT Are polarization observations possible with double position switching? • B fields in single clouds at high z via OH conjugate lines, absorption Is there an irreducible noise floor in L-band or below? • (How low can we go?)