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The EPOS view on IRDCs : The transition from pre- to proto-stellar cores

The EPOS view on IRDCs : The transition from pre- to proto-stellar cores. Hendrik Linz. Oliver Krause Henrik Beuther Sarah Ragan Thomas Henning Amelia Stutz Jürgen Steinacker Markus Nielbock Zoltan Balog Tatiana Vasyunina Bringfried Stecklum (TLS Tautenburg) Randolf Klein (UC Berkeley).

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The EPOS view on IRDCs : The transition from pre- to proto-stellar cores

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  1. The EPOS view on IRDCs :The transition from pre- to proto-stellar cores Hendrik Linz • Oliver Krause • Henrik Beuther • Sarah Ragan • Thomas Henning • Amelia Stutz • Jürgen Steinacker • Markus Nielbock • Zoltan Balog • Tatiana Vasyunina • Bringfried Stecklum (TLS Tautenburg) • Randolf Klein (UC Berkeley) • Göteborg, September 06, 2010

  2. IRDCs with Herschel Outline Star Formation in IRDCs • What are IRDCs? Where do we stand? • Our IRDC sample within EPOS • Selected results: from extinction to emission, from new Herschel detections without MIPS counterparts to brighter proto-clusters • Conclusions

  3. IRDCs with Herschel MIPSGAL 24mm, Gal. Long. 67 to 47 Courtesy Sean Carey and the MIPSGAL team MIPSGAL 70mm, Gal. Long. 67 to 47 Courtesy Sean Carey and the MIPSGAL team GLIMPSE 8mm, Gal. Long. 67 to 47 Courtesy Sean Carey, Ed Churchwell, Marilyn Meade and the GLIMPSE team Infrared look into the Galactic disk

  4. IRDCs with Herschel Infrared Dark Clouds (IRDCs) 8 µm wavelength Ed Churchwell and the GLIMPSE team

  5. What do we know about IRDCs? • Galactic plane surveys by ISO and MSX satellitesin the 1990s: ISOGAL at 7 and 14 micron MSX at 8.3, 12.1, 14.3 and 21.3 µmstrong PAH features especially in the MSX 8.3 µm band → bright extended emission • new class of interstellar clouds: high extinction (>2 mag @ 8µm)apparent in absorption against bright PAH background • Current census: almost 11,000 candidate IRDCs (Simon et al. 2006) with > 12700 identified cores (see also Peretto & Fuller 2009) • Shapes range from filamentary (very often) to compact IRDCs with Herschel

  6. First hints on the properties Initial analysis of a handful of objects by Carey et al. (1998): clouds contain cold gas < 20 K (based on H2CO temperature estimates) – confirmed by NH3 measurements with Effelsberg (Pillai et al. 2006) • SCUBA 850 micron observations: (sub)mm emission followsthe MIR absorption morphology (Carey et al. 2000) • Moderate to high cloud masses: Rathborne et al. 2006:sample of 38 IRDCs with cloud masses of 120 – 16000 Msun(median 940 Msun) and core masses of 10 – 2100 Msun(median 120 Msun) from 1.2 mm emission similar results from Spitzer analysis (Ragan et al. 2009) • Follow-up molecular line studies (e.g., Ragan et al. 2006, Sakai et al. 2008, Jackson et al. 2008, Battersby et al. 2010) IRDCs with Herschel

  7. IRDCs with Herschel Our IRDC sample for EPOS 14 IRDCs selected from target lists of three groups: Carey et al. (1998/2000): MSX objects with subsequent H2CO spectra and SCUBA mappingHennebelle/Teyssier (2001/2002): ISOGAL objects with CO analysisVasyunina et al. (2009): southern MSX objects with SIMBA 1.2 mm mapping, further chemical analysis based on Mopra spectra underway (Vasyunina et al., re-submitted) Our Strategy: Deep medium-sized maps of the objects, PACS-only and SPIRE-only scan maps with medium scan speed to ensure high sensitivity and optimal spatial resolution

  8. IRDCs with Herschel Cold high-density core appearance 7 µm 15 µm 175 µm 1300 µm Appearance of a young, close-to-collapse core against an artificial background: From absorption to emission … Image raytracing performed by J. Steinacker, Based on 3-D SPH core simulations of B. Lang & A. Burkert

  9. IRDCs with Herschel G11.11-0.12: Peeking into the Big Snake (Henning et al. 2010 ... See also Sarah Ragan‘s poster for details)

  10. IRDCs with Herschel IRDC004.36-0.06: A quiescent IRDC with newly revealed compact sources MIPS 24 micron PACS 70 micron Distance ~ 3.5 kpc Green crosses: column density peaks at 850 µm Blue circles: location of 70 µm sources not detected at 24 µm

  11. IRDCs with Herschel IRDC079.31+0.36 : An IRDC with many embedded Herschel point sources in a complex environment Distance ~ 1 kpc Carey et al. (1998) source Spitzer 3.6-8.0-24 micron com- posite by Kraemer et al. 2010 Special note: LBV in the background (at 1.7 – 2.0 kpc), in target list of Herschel KP (PI: M. Groenewegen) 0.5 pc PACS 70-100-160 micron composite

  12. IRDCs with Herschel 70 µm + 850 µm contours 70 µm + N2H+(1-0) contours

  13. IRDCs with Herschel IRDC316.72+0.07 : A southern filamentary IRDC affected by sequential star formation? Distance ~ 2.9 kpc Filamentary IRDC at the tip of a massive SF complex Spitzer 3.6-to-8.0 micron inverse grey-scale image with SEST/Simba 1.2 mm contours Title page for the proceedings of the MSF07 conference in Heidelberg (ASP Conf. Ser. 387, eds. Beuther, Linz, Henning)

  14. IRDCs with Herschel Herschel/PACS view on IRDC316.72+0.07 (observed end of August 2010) 1 pc

  15. IRDCs with Herschel Herschel/PACS view on IRDC316.72+0.07: Circumstantial evidence for elevated temperatures Our Parkes 64-m observations of NH3 (1,1) and (2,2): Tkin ~ 20 – 21 K 1 pc

  16. IRDCs with Herschel IRDC321.73+0.27: Does Spitzer already have all the answers? Distance ~ 2.1 kpc Mass of P1 is around 150 Msun (from 1.2 mm emission with O&H94 opacities) Very faint „green fuzzy“ emission at 4.5 µm in P1 Faint 24 µm point sources inside P1 3.6 – 8.0 µm 1 pc P2 P1

  17. IRDCs with Herschel IRDC321.73+0.27: Does Spitzer already have all the answers? MIPSGAL 24 µm MIPSGAL 24 µm + PACS 70 and 160 µm HCO+(1-0) contours SiO(2-1) contours

  18. IRDCs with Herschel Resumee • Herschel as the ideal tool to reveal the genuine seeds of star formation • EPOS observing mode (PACS and SPIRE separately, with medium scan speeds) proves successful for the science case • Single-dish molecular line observations bring important complementary information Future prospects: • More sophisticated modelling of continuum and molecular line data • Subsequent interferometric data to trace gas dynamics andenergetics on the core size scale

  19. IRDCs with Herschel IRDC18223-1243-south: Molecular line data reveal complementary structure information 50 km/s 45 km/s Based on HCO+ mapping with IRAM 30-m 50 km/s + 45 km/s

  20. IRDCs with Herschel Intermediate-mass star-forming core UYSO1: The boon of spatial resolution and more ... Linz et al. 2010, A&A Special Issue Distance ~ 1 kpc, Luminosity ~ 240 Lsun Strong molecular outflow and shocked H2 Core not detected for l < 70 µm Previous MIPS 70 µm data ambiguous Herschel/PACS 70 – 100 – 160 µm PACS 70 µm + SMA contours 0.5 pc

  21. IRDCs with Herschel A first preliminary comparison of the two modes EPOS view: PACS 70 µm 20“/s, PACS-only mode Hi-Gal view: PACS 70 µm 60“/s, parallel mode EPOS data: SPIRE 250 µm 30“/s, SPIRE-only

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