Life cycle of the Interstellar Medium: Stellar birth and death. Credit:: Bill Saxton, NRAO/AUI/NSF

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1 National Astronomical Observatories, C.A.S. 6 September, 2013

2 Life cycle of the Interstellar Medium: Stellar birth and death Credit:: Bill Saxton, NRAO/AUI/NSF

3 GAS PHASE INTERSTELLAR/CIRCUMSTELLAR MOLECULES - HIGH RESOLUTION (12/03) H2 KCl HNC NH3 C3S C5 C6H CH 3 HC4CN CH AlCl HCO H3O + CH4 CH3OH C 7 H, C 6 H 2 C 8 H CH + AlF HCO + H2CO SiH4 CH3SH HCOOCH3 CH 3 COOH NH PN HOC + H2CS CH2NH C2H4 CH3C2CN H 2 C 6 (lin) OH SiN HN2 + HCCH H2C3(lin) CH3CN C 6 H 2 H 2 COHCHO C2 SiO HNO HCNH+ c-c3h2 CH3NC C2H5OH (CH3)2O CN SiS HCS + H2CN CH2CN HC2CHO C2H5CN CO CO + C3 C3H(lin) NH2CN NH2CHO CH3C4H CSi SO+ C2O c-c3h CH2CO HC3NH+ HC6CN CO 2 C 4 H 2 (CH 2 OH) 2 CP + H 3 C2S HCCN HCOOH H2C4(lin) (CH3)2CO AlNC CS CH2 SiC2 HNCO C4H C5H CH3C4CN? HF SiCN SiC 3 C 5 N NO NH2 SO2 HOCO+ HC2CN CH3NH2 NH2CH2COOH? NaCN CH 2 CHOH NS H2O OCS HNCS HCCNC CH3CCH HC8CN SO H2S MgNC C2CN HNCCC CH3CHO c-c 6 H 6 HCl C2H MgCN C3O C4Si CH2CHCN HC 10 CN NaCl HCN N 2 O NaCN H 2 COH + c-ch 2 OCH 2 + ISOTOPOMERS c-ch 2 SCH 2

4 Regimes of Molecular Spectroscopy Background Source Hot Stars Embedded Massive Young Stellar Objects Warm Dust Cores (Embedded Protostars) radio HII regions, QSOs, SNRs, CMBR D. J. Paul/

5 Ss THz source Absorption cell Background object Interstellar Cloud cm Lab: n(x) = cm -3 N = cm -2 column density ISM: n(x) = cm -3 N = cm -2

6 Snow & McCall, ARA&A 2006

7 Light Hydrides before Herschel Building blocks of larger molecules For a very long time, optical absorption lines from CH, CH+ and CN have been important probes of diffuse and translucent interstellar clouds CH, CH +, CN ( ) H 2 (UV 1970) HD (UV) Then came radio/mm (1960s/70s) OH (1963), NH 3 (1968), H 2 O (1969), CH (1973), HDO, H2S and (sub)millimeter (since late 1980s) H 2 D +, D 2 H + NH 2 HDO, D 2 O, H 3 O + After 2000: CH 2 (ISO) HF (ISO)

8 H 2 Aerobee 150 Carruthers 1971

9 Interstellar cloud chemistry = ion-molecule chemistry Densities in (even dense ) interstellar molecular clouds are much lower than the best vacuum producable on Earth. Three-body encounters extremely unlikely Low T: Rates of neutral-neutral reactions very low Reactions must be exothermic Reactions must proceed without activation barrier BUT: Cosmic rays provide (some) ionization ( ionization fraction [e/h 2 ] ~ ) Ion-molecule chemistry

10 Cosmic Ray Ionisation H 2 + crp H e - H H 2 H H H 3+ : Proton transfer reactions very efficient Key to synthezising molecules Cosmic ray particles mostly protons Effective in cold dark clouds with no UV penetration. Cosmic rays also heat molecular clouds and maintain a minimum temperature of ca. 10 K. Cosmic rays are also responsible for the ionization level of dark clouds [e - ] ~ 10-7

11 Ion-molecule chemistry Reactions of molecule A with molecular hydrogen are of type: A + + H 2 AH + + H AH + + H 2 AH H Direct evidence for ion-molecule chemistry from observations of HCO +, N 2 H +, HCNH +, Other types of reactions are possible

12 Ion-molecule reactions A B C D Radiative association reactions A B AB * Dissociative recombination reactions Radical-radical reactions: CN AB Radical-stable neutral reactions e AB A B OH HNC O NH CO HCN O NCO H h Increasing exothermity

13 Formation of gaseous water H 2 + cosmic rays H e H H 2 H H H O OH + + H 2 OH n + + H 2 OH n H H 3 O + + e H 2 O + H; or OH + 2H

14 Probing the Diffuse ISM with Submillimeter Absorption Spectroscopy J. Lomberg/NASM

15 Absorption lines N l = 8p c 3 A ul ( 1- e -hn/kt ex ) ò tdv t µn l T ex A ul / Dv ( N u / g ) u / ( N l / g ) l = e - E u -E l kt ex Common assumption: LTE N tot = N u e Eu/kT rot g Q ( T ) rot u T ex = T rot = T kin High density gas = T CMB (= K) low density gas

16 At low densities, the molecular levels are thermalized at the cosmic microwave background temperature: K. A ul µn 3 S ul m 2 ij ~ cm 3 s -1 (D) (GHz) n crit (cm -3 ) CO 0.11 n x (low J) HCO n x 89 few 10 5 (low J) HF 1.83D NH few 10 3

17 CO E rot = 2 2I J(J+1) HF n µ J J = 1 59 K J = mm/345 GHz 0.24 mm/1232 GHz 5.5 K mm/230 GHz 2.6 mm/115 GHz 0

18 For compact sources, large collecting area makes the difference! S L = -h cov S ( C 1- e -t )» -h cov S t C (for t << 1) T L µs C A eff = x 50 = x 35

19 Transmission on a 5000m high site unter good, very good, and extremely good weather conditions 1200 m 250 GHz 450 m 350 m 660 GHz 860 GHz 200 m 1.5 THz average Chile Hawaii

20 14 May April 2013

21 Systems must by completely autonomous

22 HIFI (Heterodyne Instrument for the Far Infrared) GHz, 7 bands Very high resolution heterodyne spectrometer PACS (Photodetector Array Camera and Spectrometer) THz: photom x 3.5 / spec 50 5 Imaging photometer / medium resolution grating spectrometer SPIRE (Spectral and Photometric Imaging Receiver) 0.58, 0.83, 1.2 THz, 4 4 Imaging photometer / imaging Fourier transform spectrometer

23 HIFI Heterodyne Instrument for the Far-Infrared Telescope, primary and secondary mirror Antenna Local Oscillator Mixer Amplifier Bandpass Filter Spectrometer LO Subsystem: LOU Local oscillator unit LCU LO contol unit LSU LO base synthesizer FPU Focal plane unit AOS and autocorrelator

24 HIFI: and GHz seamless coverage

25 Herschel/HIFI Guaranteed Time Key Programmes HEXOS: Herschel/HIFI Observations of EXtraOrdinary Sources Complete line surveys of 5 positions in the Orion- KL and B2 molecular clouds PI: E. Bergin (U. Michigan, Ann Arbor) Sgr PRISMAS: PRobing Interstellar Molecules with Absorption Line Studies (Mostly) rotational ground-state transitions of O-, C-, and N-bearing hydrides toward selected SFRs PI: M. Gerin (LERMA Obs. de Paris/ENS)

26 C. Hieret, Diploma Thesis, MPIfR

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28 VLBA

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30 The BeSSel Team: Mark Reid (PI), Tom Dame, Sato Karl Menten, Andreas Brunthaler, Yoon Kyung Choi, Bo Zhang, Kazi Rygl, Katharina Immer, & Alberto Sanna Xing-Wu Zheng Ye Xu Kazuya Hachisuka Luca Moscadelli George Moellenbrock Anna Bartkiewicz Harvard-Smithsonian Center for Astrophysics, USA Mayumi Max-Planck-Institut für Radioastronomie, Germany Nanjing University, China Purple Mountain Observatory, Nanjing, China Shanghai Astronomical Observatory, China Osservatorio di Arcetri Observatory, Florence, Italy National Radio Observatory, USA Torun Centre for Astronomy, Poland

31 S 252 Parallax: using CH 3 OH masers Maser 2 3 QSOs; Maser 1 Reid et al (2009) p = / mas

32 BeSSeL Parallaxes: Example Parallax for W 49N H 2 O masers P = 90 ± 6 as (D=11.1 ± 0.8 kpc) Zhang et al. 2013

33 The BeSSeL Survey Preliminary results of parallaxes from VLBA, EVN & VERA: ~ 100 sources Arms assigned by CO l-v plot Tracing most spiral arms 4. Inner, bar-region is complicated Background: artist conception by Robert Hurt (NASA: SSC)

34 D = 11.1 ± 0.9 kpc D = 7.8 ± 0.7 kpc D = 2.49 ± 0.19 kpc D = 5.0 ± 0.5 kpc D = 5.4 ± 0.3 kpc D = 1.50 ± 0.08 kpc

35 The Background Sources: Cold or Warm Dust from Protostellar Condensations T D = 32 K Sgr B2 Lis & Goldsmith 1990

36 APEX APEX

37 The Atacama Pathfinder Experiment (APEX) Built and operated by Max-Planck-Institut fur Radioastronomie Onsala Space Observatory European Southern Observatory on Llano de Chajnantor (Chile) Longitude: W Latitude: S Altitude: m 12 m = 200 m 2 mm 15 m rms surface accuracy in full operation sice autumn 2006 PI and facility instruments: GHz heterodyne RX 350 and 870 m bolometer cameras

38 Chajnantor SW from Cerro Chajnantor, 1994 May AUI/NRAO S. Radford

39 average over man l.o.s.

40 APEX

41 How to get H and H 2 column densities Direct determination of HI column density by interferometry (+ emission mapping) of 21 cm line mm absorption interferometry of lines of H 2 column density proxies and other interesting species Complementary: cm absorption interferometry of (near) ground state lines from: OH (1612, 1665, 1667, and 1720 MHz) CH (3264, 3335, and 3349 MHz H 2 CO (4830 and MHz) C 3 H 2 (18343 MHz)

42 τ(hi): measures diffuse gas column Possible dense + diffuse gas H 2 proxy Possible diffuse gas H 2 proxy Menten et al. 2011

43 Determination of HI Column Densities with the Lazareff (1975) Technique delivers τ T s delivers T B ( ) ( v) = T B 1- exp -t v [ ] N ( H cm -2 ) = ò tt s ( K)dv( km s -1 ) Dickey et a. 1983

44 Menten et al. 2011

45 K. G. Jansky Very Large Array (JVLA) Observations An Expanded Very Large Array absorption data for the 1420 MHz HI and the 1612, 1665, 1667, and 1720 MHz OH transitions (21 and 18 cm) of PRISMAS sources G , G , W 51, W 49 N, DR21(OH) Also, an Effelsberg 100 meter HI emission data and OH data

46 Herschel FWHM/500 GHz

47 W 51 HI 21 cm

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49 [H 2 Cl + ]~[HCl]

50 [O(H 2 O)]/[P(H 2 O) = 2.5 Þ T = 27K

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52 The interstellar CH + abundance problem even gets aggravated!

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54 HF in the ISM Fluorine is the only atom that can react exothermically with H 2 to form a diatomic hydride: F + H 2 HF + H +1.4eV HF is destroyed very slowly by means of cosmic ray-induced photodissociation and as a result of reactions with species of low abundances such as He +,H 3+, and C +. HF is expected to be the dominant reservoir of gas-phase fluorine. N(HF)/N(H 2 ) ~ 3.6 x 10-8 HF may be used as a valuable surrogate tracer for molecular hydrogen within the diffuse interstellar medium, both in the Milky Way and other galaxies. R. Monje

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56 + 44 others Strong involvement of laboratory people

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58 Basic Oxygen Chemistry Nagy/Tielens & Hollenbach

59 Basic Carbon Chemistry Nagy/Tielens & Hollenbach

60 Results so far and future developments: Submillimeter observations of rotational ground-state transitions have greatly enhanced our view of diffuse ISM chemistry added missing pieces have extended chemistry studies throughout the Galaxy delivered new HI/H 2 tracers This new information will allow addressing questions on Galactocentric abundance gradients effects of lower metallicity in Outer Galaxy

61 Galactic molecular absorption spectroscopy after Herschel

62 Stratospheric Observatory for For Infrared Astronomy (SOFIA) 2.7 m telescope US/German (NASA/DLR) 80%/20% joint project m ( THz) wavelength/frequency range GREAT und STAR instruments from Bonn/Köln/Berlin-Adlershof First science flight Project duration > 20 years OH 2 P 3/2 J = (2.51 THz) HD J = 1-0 (2.67 THz)

63 German Receiver for Astronomy at THz Frequencies MPIfR KOSMA MPS DLR-Pf ATM 1-5 THz, 14 km altitude

64 GREAT - the Consortium MPIfR KOSMA MPS DLR-Pf GREAT, L#1 & L#2 channels PI-Instrument funded and developed by MPI Radioastronomie (2.7 THz channel) R. Güsten (PI) S. Heyminck (system engineer) B. Klein (FFT spectrometer) I. Camara, T. Klein (2.7 THz LO) Univ. zu Köln, KOSMA (1.4/1.9THz channels) J. Stutzki (Co-PI) U. Graf (1.4 &1.9THz LO, Optics) K. Jacobs (HEB mixers up to 2.7 THz) R. Schieder (array-aos) DLR Planetenforschung (4.7 THz channel) H-W. Hübers (Co-PI: 4.7 THz HEB, IF, cal unit) MPI Sonnensystemforschung P. Hartogh et al. (CO-PI: CTS)

65 Configuration - overview MPIfR KOSMA MPS DLR-Pf Channel Frequencies [THz] Lines of interest low-frequency L1 a,b [NII], CO series, OD, HCN, H 2 D + low-frequency L2 a,b NH 3, OH, CO(16-15), [CII] mid-frequency M a,b 2.5, 2.7 OH( 2 P 3/2 ), HD high-frequency H 4.7 [OI] two out of the 4 cryostats can be operated simultaneously all channel combinations are possible the actual flight configuration is science driven (within our operational limitations) channel availability all of low-frequency channels operational (baseline for Basic Science) have been flown routinely now since April mid frequency channels (just in time delivery for late July flights) successful engineering flights in July high-frequency channel (upgrade foreseen in 2012)

66 Wiesemeyer et al. 2012

67 W49N [H 2 O]/[[OH] ~ W51E Wiesemeyer et al. 2012

68 APEX (Much) more OH + with Wyrowski et al. (in prep.)

69 Use submm results to calibrate data of easily observable, but non-thermally excited cm lines density proxies Palmer et al Liszt & Lucas 1995 H 2 CO 4.8 GHz

70 CH 2 P 1/2 J = 1 2 (3264, 3235, 3349 MHz) Genzel et al Hfs lines are always (weakly) inverted

71 Wiesemeyer et al. 2012

72 OH 2 P 3/2 ground-state transitions satellite lines main lines

73 Han 2009

74 Some Conclusions: Molecular (sub)millimeter absorption spectroscopy has transformed our knowledge of diffuse ISM chemistry Herschel has left a rich heritage on which we can build with SOFIA and high altitude ground based submm observatories and at high redshift with ALMA! The submm data can be used to calibrate cmwavelength data of important molecules that are difficult to interpret on their own, but can provide important information, e.g., on magnetic fields

75 Thanks for your attention

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78 Half-power beamwidth Full width at half maximum (FWHM) 1.22 /D

79 Effelsberg 100m 1.22 /D IRAM 30m APEX 12m B = 44 GHz B = 112 GHz B = 380 GHz (Telescopes are not reproduced on same scale)

80 D Single antenne: = /D Interferometer: = /B B VLA VLBA Largest structure that can be imaged given by telescope diameter zero spacing problem

81