1 / 50

Radio Selected Damped Lyman  Systems

Radio Selected Damped Lyman  Systems. Jeremy Darling (CASA, University of Colorado). Outline: 1. Damped Lya Systems 2. Motivation 3. Intervening Absorption 4. Intrinsic Absorption [5. H 2 CO Absorption] 6. Summary. Damped Lyman  Systems. By definition,

tori
Download Presentation

Radio Selected Damped Lyman  Systems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Radio Selected Damped Lyman  Systems Jeremy Darling (CASA, University of Colorado) Outline: 1. Damped Lya Systems 2. Motivation 3. Intervening Absorption 4. Intrinsic Absorption [5. H2CO Absorption] 6. Summary

  2. Damped Lyman  Systems By definition, For the 21 cm HI line, In practice, we’ll refer to DLAs as any sufficient column, regardless of host or setting. NHI≥2  1020 cm-2 NHI= 1.8  1018 cm-2 (Tspin / )   d

  3. DLAs: Motivation for 21 cm Searches Optical spectroscopic selection: Requires background UV source Redshift into atmospheric window (z > 1.65) Pencil beam (single los, single cloud) DLA studies: Damped/saturated line (very important for EOR studies!) Optical identification of DLAs Molecular absorption: Extremely rare Requires dust Fundamental physics Gastrophysics

  4. DLAs: Motivation for 21 cm Searches Optical spectroscopic selection: Requires background UV source Redshift into atmospheric window (z > 1.65) Pencil beam (single los, single cloud) DLA studies: Damped/saturated line (very important for EOR studies!) Optical identification of DLAs Molecular absorption: Extremely rare Requires dust Fundamental physics Gastrophysics HI 21 cm: Dust! Any z Multiple los, clouds (+ Einstein rings!) 21 cm HI:  = 0.01-0.10 (cf Radio Probes of Reionization, 2007) Optically faint QSOs All molecular absorbers show HI 21 cm absorption

  5. Molecular Absorbers: The Usual Suspects • Molecular Absorbers: • Four known at z > 0.2 • (OH only excluded) • Large searches have produced no new objects • Molecular Absorption • Requires fortuitous alignment • Requires flat or inverted continuum • Detectability is independent of redshift • Gastrophysics • Provides only means to detect unexceptional ISM at z > 0 • Precision Measurements • Can measure fundamental constants at high redshift

  6. Molecular Absorption Systems at z > 0.2 • PKS 1413+135 • z = 0.2467 • AGN in spiral • B3 1504+377 • z = 0.6734 • AGN in spiral • B 0218+357 • z = 0.6847 • Lens (Einstein ring) • PKS 1830-211 • z = 0.8858 • Lens (Einstein ring) • Conjugate OH lines • No “main” lines Wiklind & Combes 1997 Darling (2004) Darling (in prep) Wiklind & Combes 1996 Darling (in prep) Kanekar et al 2003 Wiklind & Combes 1995 Kanekar et al 2003 Wiklind & Combes 1998 Darling (in prep)

  7. Molecular Absorption Systems at z > 0.2 • PKS 1413+135 • z = 0.2467 • AGN in spiral • B3 1504+377 • z = 0.6734 • AGN in spiral • B 0218+357 • z = 0.6847 • Lens (Einstein ring) • PKS 1830-211 • z = 0.8858 • Lens (Einstein ring) • Conjugate OH lines • No “main” lines Wiklind & Combes 1997 Darling (2004) Darling (in prep) Wiklind & Combes 1996 Darling (in prep) Kanekar et al 2003 Wiklind & Combes 1995 Kanekar et al 2003 Wiklind & Combes 1998 Darling (in prep)

  8. 13 km s-1 PKS 1413+135: OH and HI Absorption OH satellite lines: 1612, 1720 MHz (see also Kanekar et al. 2004) Systematic offset from HI Is the offset physical? How to assess offsets?

  9. (1×10-5 ~ 10 km s-1) PKS 1413+135: OH, HI & CO HI, CO redshifts exceptionally well measured (< 10-6);systematics dominate (Carilli et al. 1998) OH:Systematic offset from HI, CO OH-only measure consistent with zero Δν/HI:systematics can account forallΔα/αo HI: Darling 2004 OH: Darling 2004 CO: Wiklind & Combes 1997

  10. PKS 1413+135: OH, HI & CO HI, CO redshifts exceptionally well measured (< 10-6);systematics dominate OH:Systematic offset from HI, CO OH-only measure consistent with zero Δν/HI:systematics can account forallΔα/αo

  11. Intervening 21 cm Absorption: A “blind” survey at Green Bank Goals: Conduct a DLA search analogous to optical surveys (large ∆z). Minimize DLA selection biases (z, dust). Requires: Large instantaneous z coverage Good velocity resolution (∆v < 10 km s-1) Sensitivity to all DLAs in short integrations Bonus: Simultaneous search for OH lines Two Surveys: 1. 100 continuum sources (S > 0.8 Jy) in 0.6 < z < 1.1 (Darling & Giovanelli) 2. 182 flat-spectrum sources from z = 0 to z = zsys(Bolatto & Darling)

  12. Green Bank Blind HI Survey: Observe 200 MHz at 800 MHz with 6 kHz (~2 km s-1) resolution λ /Δλ = 132,000 BW/λ = 0.25 Radio Freq Interference (RFI) is problematic and reduces z coverage Feed Resonance RFI z = 1.1 tl = 8.1 Gyr tU = 5.6 Gyr z = 0.63 tl = 5.9 Gyr tU = 7.8 Gyr 2.2 Gyr, 1.2 Gpc

  13. Chengalur, deBruyn, & Narasimha 1999 Patnaik et al. 1994 Nair et al. 1993 PKS 1830-211 FWHM = 57 km s-1 τc = 0.22 NHI = 24.3 x 1018 (Ts/f) cm-2 Green Bank Blind HI Survey Pure radio HI absorption detection! Proof-of-concept for blind searches. • Molecules? • Lens?

  14. Chengalur, deBruyn, & Narasimha 1999 Patnaik et al. 1994 Nair et al. 1993 FWHM = 57 km s-1 τc = 0.22 NHI = 24.3 x 1018 (Ts/f) cm-2 Green Bank Blind HI Survey BIMA (Bolatto) Pure radio HI absorption detection! Proof-of-concept for blind searches. PKS 1830-211 • Molecules? • Lens?

  15. Intervening 21 cm Absorption: A “blind” survey at Green Bank Goals: Conduct a DLA search analogous to optical surveys (large ∆z). Minimize DLA selection biases (z, dust). Requires: Large instantaneous z coverage Good velocity resolution (∆v < 10 km s-1) Sensitivity to all DLAs in short integrations Proof of Concept: Detection of 2351+456 at z = 0.78 (no a priori knowledge of this DLA) Recovery of known absorbers Expectations: ∆z ~ 150 (including RFI losses) Estimate of ΩHI(but depends on Tspin)

  16. Intrinsic 21 cm Absorption: CSOs Compact Symmetric Objects: Compact (< 1 kpc) Symmetric (jets) Post-Mergers Inside-out virialization (t ~ 108 yr, Perlman et al 2001) Jet advance shows radio source turn-on Crossing time of nucleus « jet lifetime  nucleus at birth of RL AGN Dust and gas still in cores (yet to be expelled) Peck & Taylor 2002

  17. Intrinsic Absorption: Survey Expectations Observe: 71 sources 0.5 < z < 4 CSOs GPS sources CSS sources Expect: Detect all DLAs in 1-2 hours Bonus: OH lines  DLAs 

  18. Intrinsic Absorption Expected HI

  19. Intrinsic Absorption Expected HI PKS 0500+019 z = 0.58 Flux Density (Jy) Previous detection: Carilli et al 1998 Barycentric Frequency (MHz)

  20. Intrinsic Absorption: Survey Results (so far…) z < 0.7 redetections

  21. Intrinsic Absorption: Survey Results (so far…) No new detections Previous surveys have 30-50% detection rate atz < 0.7 (Vermeulen et al 2003) Sub-DLAs detectable Adequate sensitivity to z ~ 3, including RFI losses Work continues… z < 0.7 redetections

  22. NGC 2264 Darling & Goldsmith (in prep) H2CO: The Swiss Army Knife Molecule Galactic Extragalactic Gastrophysics Galaxy Evolution (Cosmology ?)

  23. 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)

  24. 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.

  25. 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)

  26. 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

  27. Darling & Wiklind Ortho-H2CO Toward B0218+357 • 4.8 GHz (110-111) line detected at Arecibo • Two gaussian components • app = 0.013 ± 0.003 • ∆v = 12.6 ± 0.6 km s-1 • Previous Detections: • 14.5 GHz (211-212) (VLA; Menten & Reid 1996) • 150.5 GHz (211-110) (IRAM; Wiklind & Combes) Wiklind & Combes

  28. H2CO Toward B0218+357: Summary • Similar to Galactic Dark Clouds (but scaled to CMB at z = 0.67) • Centimeter lines (4.8, 14.5 GHz) are anti-inverted • T4.8 ~ 2.3 K • T14.5 ~ 3.4 K (TCMB = 4.6 K) • Millimeter lines (150.5, 140.8 GHz) have Tex ~ TCMB • N(ortho-H2CO) = 1.5  1013 cm-2 • N(H2) = 1.5  1021-22 cm-2 • n(H2) = 104-5 cm-3 • Future Prospects: • Ortho:para at z > 0 • Prediction: H2CO can be observed in absorption against CMB in extragalactic ISM • - How does T decrement scale with z? • - What is H2CO filling factor?

  29. H2CO Absorption Against the CMB

  30. 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 probe of dense molecular gas, independent of redshift!

  31. H2CO Against the CMB: Prospects • Step 1:Local Calibration • Survey local galaxies, from spirals to ULIRGs • Include sample with CO and HCN measurements • What is the filling factor on kpc scales? • What is the total H2CO mass? M(H2CO)  M(dense) • GBT: large survey in 14.5 and 4.8 GHz lines • (Darling, Mangum, Menten, & Henkel) • Step 2:Submm Galaxies • How does anti-inversion scale with redshift? • What is dense gas fraction? • VLA: deep integrations in 312 - 313 line at z ~ 2.5 (Darling & Baker)

  32. Radio-Selected Damped Lyman  Systems • New Radio Facilities Allow Optical-Style Surveys • Intervening absorption, independent of dust • Proof of concept detection of DLA • ∆z ~ 150 • Intrinsic Absorption • Expect high detection rates • Sensitivie to DLAs to z = 4 • OH search for free • Stimulated Absorption by H2CO (DASARs) • Uses CMB as illumination source • Traces gastrophysics in detail • Potentially very large pool of objects to observe • (still much foundational/calibration work to be done…)

  33. The End

  34. Conjugate OH: Anti-masing Conjugate OH lines: Selection rules: ΔF = ± 1,0 Intra-ladder transitions overpopulate F = 2: 1720 emission 1612 absorption Inter-ladder transitions overpopulate F = 1: 1720 absorption 1612 emission 1720 1612

  35. Conjugate lines in NGC 253 Frayer, Seaquist & Frail (1998) Conjugate OH lines show changing structure along line of sight: 1720 emission  N(OH)/V < 1015 cm-2 km-1 s  N(H2) < 1022 cm-2 1612 emission  N(OH)/V > 1015 cm-2 km-1 s  N(H2) > 1022 cm-2 Note: Conjugate lines weakly amplify background continuum  Detectability follows rules of absorption, not emission

  36. H2CO Absorption in Dark Clouds “Anomalous absorption” in Galactic dark clouds (Palmer et al 1969)  Tex < TCMB • 2 cm lines also observed in absorption against CMB • “Anti-inversion” due to collisional pumping (Evans et al 1975) • cm line ratio proxy for n(H2) 2 mm emission observed in Galactic dark clouds (Evans & Kutner 1976)  gastrophysics

  37. H2CO: The Swiss Army Knife Molecule Anti-inverted (cm) line ratios yield n(H2), nearly independent of Tkin • Line ratios between species give ortho:para ratio • H2CO formation channel (hot/cold; gas/dust) Line ratios from different Ka ladders of a given species (ortho/para) yield Tkin ∆J = ±1 line ratios within a Ka ladder yield Trot

  38. Baan, Guesten, & Haschick (1986) 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 Darling & Henkel

  39. 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 Darling & Henkel (in prep) NGC 660, 8.4 GHz Filho, Barthel, & Ho (2002)

  40. 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 Darling & Henkel (in prep) ~375 km/s NGC 660, 8.4 GHz ~350 pc Mencl = 1.4109 M Filho, Barthel, & Ho (2002)

  41. H2CO: A Planar Asymmetric Top Molecule Wiklind & Combes

  42. H2CO: Anti-Inversion in Centimeter Lines Allow 4 excitation temps: No physical solution with Tcm > TCMB No solution with Tmm= Tcm No solution with Tmm= T4.8 If T14.5 = T4.8 then all lines have Tex < TCMB If Tmm ≥ TCMB then TCMB > T14.5 > T4.8

  43. Chengalur, deBruyn, & Narasimha 1999 Patnaik et al. 1994 Nair et al. 1993 Extended Illumination: PKS 1830-211 PKS 1830-211: - Einstein ring at z = 0.89 - HI and OH absorption - CO, HCN, HCO+,… absorption - Moleculear isotope absorption - H2CO absorption PKS 1830-211 Menten et al. 1999 300 km/s Darling (in prep)

  44. Scaling Relations • Detection of cm H2CO Lines vs z Depends on: • (Anti) Inversion vs z • How does Tcm - TCMB scale vs z? • (TCMB = 2.73 (1+z) K) • Filling factor on kpc scales • Filling factor vs z • Angular size vs z

  45. Scaling Relations • Detection of cm H2CO Lines vs z Depends on: • (Anti) Inversion vs z • How does Tcm - TCMB scale vs z? • Tcm - TCMB (1+z) • Filling factor on kpc scales • Filling factor vs z • Angular size vs z

  46. Scaling Relations • Detection of cm H2CO Lines vs z Depends on: • (Anti) Inversion vs z • How does Tcm - TCMB scale vs z? • Tcm - TCMB (1+z) • Filling factor on kpc scales • Filling factor vs z • Angular size vs z

  47. Scaling Relations • Detection of cm H2CO Lines vs z Depends on: • (Anti) Inversion vs z • How does Tcm - TCMB scale vs z? • Tcm - TCMB (1+z) • Filling factor on kpc scales • Filling factor vs z • Angular size vs z • - CMB power in small beams Rayleigh-Jeans Law  CMB power scales as beam arcmin:arcsec  3600:1 ~100 mJy  ~30 µJy

  48. H2CO Against the CMB: Prospects The Future: - Molecule of choice for studies of star formation, molecular gas from present day to arbitrary redshift EVLA ALMA High Sensitivity Array Ortho:Para H2CO gives astrochemistry channel (dust vs gas, hot vs cold) H2CO mm + cm lines yield gastrophysics Tkin n(H2) Tx TCMB No redshift limit to detection (in fact, angular size grows at high z)

  49. H2CO as z-Machine • If H2CO can be observed against the CMB, • Anti-inversion obviates need for chance alignments • Unique probe of gastrophysics of dense molecular ISM • Much foundational work yet to be done… • Scaling relations • Filling factor on kpc scales • Total H2CO mass in galaxies: M(H2CO)  M(dense) • Regardless, H2CO should be observable with ALMA: • Absorption and emission • Similar abundance, line luminosity to HCN (~10%) • Ortho:para H2CO at z > 0 • Line Tex floor set by CMB, scales with z

  50. Pathologies as Probes • Masers provide exceptional Tb • Precision positions (H2O in NGC 4258) • Probes of intervening gas (scintillation) • Signposts at cosmological distances • Tunneling • NH3 is a maser and molecular ISM thermometer • Conjugate Lines • Local H2 density indicator • Probe of fundamental physical constants • Stimulated Absorption (DASARs) • Uses CMB as illumination source • Traces gastrophysics in detail • Potentially very large pool of objects to observe • (still much foundational/calibration work to be done…)

More Related