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

Hendrik Linz

Göteborg, September 06, 2010

Oliver KrauseHenrik BeutherSarah Ragan

Thomas HenningAmelia Stutz

Jürgen SteinackerMarkus Nielbock

Zoltan BalogTatiana Vasyunina

Bringfried Stecklum (TLS Tautenburg)Randolf Klein (UC Berkeley)

IRDCs with Herschel

Outline

Star Formation in IRDCsStar 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

IRDCs with Herschel

Infrared look into the Galactic disk

MIPSGAL 24m, Gal. Long. 67 to 47Courtesy Sean Carey and the MIPSGAL team

MIPSGAL 70m, Gal. Long. 67 to 47Courtesy Sean Carey and the MIPSGAL team

GLIMPSE 8m, Gal. Long. 67 to 47Courtesy Sean Carey, Ed Churchwell, Marilyn Meade and the GLIMPSE team

IRDCs with Herschel

Ed Churchwell and the GLIMPSE team

Infrared Dark Clouds Infrared Dark Clouds (IRDCs)(IRDCs)

8 µm wavelength8 µm wavelength

IRDCs with Herschel

What do we know about IRDCs?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

First hints on the propertiesFirst 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

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 mapping

Hennebelle/Teyssier (2001/2002): ISOGAL objects with CO analysis

Vasyunina 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

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

IRDCs with Herschel

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

IRDCs with Herschel

IRDC004.36-0.06: A quiescent IRDC with newlyIRDC004.36-0.06: A quiescent IRDC with newly revealed compact sources revealed compact sources

MIPS 24 micron PACS 70 micronMIPS 24 micron PACS 70 micron

Distance ~ 3.5 kpcGreen crosses: column density peaks at 850 µmBlue circles: location of 70 µm sources not detected at 24 µm

IRDCs with Herschel

IRDC079.31+0.36 : An IRDC with many embedded HerschelIRDC079.31+0.36 : An IRDC with many embedded Herschel point sources in a complex environmentpoint sources in a complex environment

0.5 pc0.5 pc

Distance ~ 1 kpc Distance ~ 1 kpc

Carey et al. (1998) sourceCarey et al. (1998) source

Spitzer 3.6-8.0-24 micron com-Spitzer 3.6-8.0-24 micron com- posite by Kraemer et al. 2010posite by Kraemer et al. 2010

Special note: LBV in the Special note: LBV in the background (at 1.7 – 2.0 kpc),background (at 1.7 – 2.0 kpc), in target list of Herschel KP in target list of Herschel KP (PI: M. Groenewegen)(PI: M. Groenewegen)

PACS PACS 7070--100100--160160micron compositemicron composite

IRDCs with Herschel

70 µm + 850 µm contours70 µm + 850 µm contours 70 µm + N70 µm + N22HH++(1-0) contours(1-0) contours

IRDCs with Herschel

IRDC316.72+0.07 : A southern filamentary IRDC affected byIRDC316.72+0.07 : A southern filamentary IRDC affected by sequential star formation?sequential star formation?

Distance ~ 2.9 kpc Distance ~ 2.9 kpc

Filamentary IRDC at the tip ofFilamentary IRDC at the tip of a massive SF complexa massive SF complex

Spitzer 3.6-to-8.0 micron inverse Spitzer 3.6-to-8.0 micron inverse grey-scale image withgrey-scale image with SEST/Simba 1.2 mm contoursSEST/Simba 1.2 mm contours

Title page for the proceedingsTitle page for the proceedings of the MSF07 conference inof the MSF07 conference in Heidelberg (ASP Conf. Ser.Heidelberg (ASP Conf. Ser. 387, eds. Beuther, Linz, 387, eds. Beuther, Linz, Henning)Henning)

IRDCs with Herschel

1 pc

Herschel/PACS view on IRDC316.72+0.07Herschel/PACS view on IRDC316.72+0.07 (observed end of August 2010)(observed end of August 2010)

IRDCs with Herschel

Our Parkes 64-m observations Our Parkes 64-m observations of NHof NH33 (1,1) and (2,2): (1,1) and (2,2):

TTkinkin ~ 20 – 21 K ~ 20 – 21 K

1 pc

Herschel/PACS view on IRDC316.72+0.07:Herschel/PACS view on IRDC316.72+0.07:Circumstantial evidence for elevated temperaturesCircumstantial evidence for elevated temperatures

IRDCs with Herschel

IRDC321.73+0.27: Does Spitzer already have all the answers?IRDC321.73+0.27: Does Spitzer already have all the answers?

3.6 – 8.0 µm Distance ~ 2.1 kpc Distance ~ 2.1 kpc

Mass of P1 is around Mass of P1 is around 150 M150 Msunsun

(from 1.2 mm emission (from 1.2 mm emission with O&H94 opacities)with O&H94 opacities)

Very faint Very faint „„green fuzzygreen fuzzy““ emission at 4.5 µm in P1emission at 4.5 µm in P1

Faint 24 µm point Faint 24 µm point sources inside P1sources inside P1

P1P1P2P2

1 pc1 pc

IRDCs with Herschel

MIPSGAL 24 µmMIPSGAL 24 µmMIPSGAL 24 µm + PACS 70 and 160 µmMIPSGAL 24 µm + PACS 70 and 160 µmHCO+(1-0) contoursHCO+(1-0) contoursSiO(2-1) contoursSiO(2-1) contours

IRDC321.73+0.27: Does Spitzer already have all the answers?IRDC321.73+0.27: Does Spitzer already have all the answers?

IRDCs with Herschel

Resumee

Herschel as the ideal tool to reveal the genuine seeds of star Herschel as the ideal tool to reveal the genuine seeds of star formationformation

EPOS observing mode (PACS and SPIRE separately, with EPOS observing mode (PACS and SPIRE separately, with medium scan speeds) proves successful for the science casemedium scan speeds) proves successful for the science case

Single-dish molecular line observations bring important Single-dish molecular line observations bring important complementary information complementary information

Future prospects:Future prospects:

More sophisticated modelling of continuum and molecular line More sophisticated modelling of continuum and molecular line datadata

Subsequent interferometric data to trace gas dynamics andSubsequent interferometric data to trace gas dynamics andenergetics on the core size scale energetics on the core size scale

IRDCs with Herschel

45 km/s50 km/s

50 km/s + 45 km/s50 km/s + 45 km/s

IRDC18223-1243-south: Molecular line data reveal IRDC18223-1243-south: Molecular line data reveal complementary structure informationcomplementary structure information

Based on HCO+ mapping with IRAM 30-m

IRDCs with Herschel

Intermediate-mass star-forming core UYSO1: The boon of spatial resolution and more ...

Herschel/PACS70 – 100 – 160 µm

PACS 70 µm +SMA contours

Distance ~ 1 kpc,

Luminosity ~ 240 Lsun

Strong molecular outflow and shocked H2

Core not detected for < 70 µm

Previous MIPS 70 µm data ambiguous

Linz et al. 2010, A&A Special Issue

0.5 pc

IRDCs with Herschel

A first preliminary comparison of the two modes

EPOS view: PACS 70 µm20“/s, PACS-only mode

Hi-Gal view: PACS 70 µm60“/s, parallel mode

EPOS data: SPIRE 250 µm30“/s, SPIRE-only