First high-resolution 3D inversion of the dust emission in Galactic ISM with Spitzer/Herschel. The case region [l,b]=[30,0] A. Traficante, R. Paladini, A. Noriega-Crespo, M. Compiegne, S. Molinari, P. Natoli et al.

Outline 1.The contest and the inversion model overview 2. New data capabilities 3. The selected region 4. Results and emissivities interpretation 1. Conclusions A. Traficante et al. Tor Vergata/Caltech MW /09/11

The contest Dust is a fundamental ISM component dust grains re-radiate stellar photons UV IR - mm tracer of star formation activity, radiation field intensity, … A. Traficante et al. Tor Vergata/Caltech MW /09/11 Infrared maps are a blending of dust emission associated with gas in different phases along the line of sight (LOS) = ++

Inversion dust model Atomic, Molecular Ionized hydrogen constant dust-to-gas ratio one dust temperature in each gas phase as a function of Galactocentric distance Uncorrelated regions along LOS A. Traficante et al. Tor Vergata/Caltech MW /09/11 Infrared maps are a blending of dust emission associated with gas in different phases along the LOS Bloemen et al. 1990

A. Traficante et al. Tor Vergata/Caltech MW /09/11 Inversion history Data availability (H + ) Bloemen et al. 1990; Giard et al. 1994; Sodroski et al. 1997; Paladini et al. 2007; Planck Coll. et al Gas phaseRadio Tracer HI21 cm line H2H2 12 CO H+H+ free-free continuum – if considered! ( e.g., Giard et al. 1994) “the spatial correlation between the ionized medium and the molecular hydrogen along the LOS has to be separated” (Sodroski et al. 1989, Paladini et al. 2007) Requirements:  ring selection  statistical approach  Column density estimation Limits: Results:average Galactic dust properties Data Resolution:0.7° - 1° AIM: Recovery of Galactic dust properties over the full sky (or a big chunk of it)

A. Traficante et al. Tor Vergata/Caltech MW /09/11 New data capabilities Spitzer Legacy surveys GLIMPSE 8 μ m\MIPSGAL 24 μ m Band (μm) Angular Res. (arcsec) Benjamin et al Carey et al Molinari et al Traficante et al Herschel Galactic Plane survey Hi-GAL μ m Hi-PASS ZOA survey 6 cm Angular Resolution 900” Staveley-Smith et al Alves et al Radio Recombination Lines (RRLs) Velocity Res km/s IRIR RADIORADIO

A. Traficante et al. Tor Vergata/Caltech MW /09/11 Local ISM study AIM: Requirements: Testing inversion method on high resolution data using a selected region of the Galactic Plane (2° x 2°): Hi-GAL tile centered on (l,b)=(30,0). We want to take into account the specific physical content of this region. We want also to test the limits of this approach.  ring selection  column density estimation Gas phaseRadio Tracer HI21 cm line H2H2 12 CO & 13 CO H+H+ RRLs Data Resolution: 15’ spatial resolution

A. Traficante et al. Tor Vergata/Caltech MW /09/11 The region Hi-GAL l=30° 2° x 2° degrees Hi-GAL tile centered on (l,b)=(30,0) 30 HII regions (Paladini et al. 2003) the brightest: W43 (Bally et al. 2010) ~75 molecular clouds (Rathborne et al. 2009) ~ 340 IRDC (Peretto et al. 2010) HI cold features (Gibson et al. 2004) Diffuse emission properties (Bernard et al. 2010, Paradis et al. 2010) Difficulties due to the confusion along the LOS W43

A. Traficante et al. Tor Vergata/Caltech MW /09/11 Requirements: rings selection Tangent point: ≈4.25 Kpc Scutum-Crux arm intersection 4.25 ≤ R ≤ 5.6 Kpc 5.6 ≤ R ≤ 7.4 Kpc 7.4 ≤ R ≤ 8.5 Kpc 8.5 ≤ R ≤ 16.0 Kpc Russeil, D. 2003

A. Traficante et al. Tor Vergata/Caltech MW /09/11 Requirements: HI and H 2 column densities VGPS survey Stil et al Angular Res. 60” Velocity Res. 1.3 Km/s T s highest T b along the LOS T s = 140 K Strasser et al e.g. Binney & Merrifiled 1998 HI H2H2 12 CO UMSB survey Sanders et al Angular Res. 44”(180”) Vel. Res. 1 Km/s 13 CO GRS survey Jackson et al Angular Res. 46” Vel. Res Km/s 12 CO only regions X CO = 1.8 Abdo et al CO + 13 CO regions Excitation temperature 12 CO & 13 CO Optical depth 12 CO & 13 CO Column density estimation Pineda et al. 2010; Duval et al. 2010

A. Traficante et al. Tor Vergata/Caltech MW /09/11 Requirements: H + column density Hi-PASS ZOA survey Staveley-Smith et al Angular Res. 900” Velocity Res km/s Radio Recombination Lines (RRL) H166α H167α H168α H+H+ Alves et al Sodroski et al cm -3 W43 peak 0.39 cm -3 diffuse T e = 5500 K Alves et al. 2010

A. Traficante et al. Tor Vergata/Caltech MW /09/11 Results: Scutum-Crux ring Atomic phase Ionized phase Molecular phase DustEM fit, Compiegne et al. 2011

A. Traficante et al. Tor Vergata/Caltech MW /09/11 Results: Scutum-Crux ring GAS phasesDust temperature (K) Atomic19.52 ± 0.71 Molecular19.91 ± 1.51 Ionized23.15 ± 1.02 Atomic phase Molecular phase DustEM fit, Compiegne et al GAS phasesY PAH Atomic1.83 ± 0.35 Molecular0.97 ± 0.31 Ionized0.72 ± 0.25

A. Traficante et al. Tor Vergata/Caltech MW /09/11 Discussion: other rings Q: The model does not fully converge. Why? A: If the gas is not entirely traced (dark gas, Grenier et al )  the column densities are underestimated  the model calculates wrong emissivities Missing column density  less correlation column density maps – infrared maps: Pearson’s correlation coefficients Hi-GAL 250 μm Ring 1Ring 2Ring 3Ring 4 HI H2H H+H

A. Traficante et al. Tor Vergata/Caltech MW /09/11 Discussion: other rings Hi-GAL 250 μm Ring 1Ring 2Ring 3Ring 4 HI H2H H+H Q: The model does not fully converge. Why? A: If the gas is not entirely traced (dark gas, Grenier et al )  the column densities are underestimated  the model calculates wrong emissivities Missing column density  less correlation column density maps – infrared maps: Pearson’s correlation coefficients

A. Traficante et al. Tor Vergata/Caltech MW /09/11 Gibson et al Hi-GAL 250μm HI: 7.4 < R < 8.5 Kpc W43 Discussion: HI ring 3 Pearson’s coeff. =

A. Traficante et al. Tor Vergata/Caltech MW /09/11 Gibson et al Hi-GAL 250μm HI: 7.4 < R < 8.5 Kpc W43 Discussion: HI ring 3 Wrong column density estimation Negative Emissivities Absorption features Anticorrelated region

A. Traficante et al. Tor Vergata/Caltech MW /09/11 The model with no H + Without considering ionized hydrogen component the model distributes the excess in particular to the most correlated component Dust associated with ionized hydrogen was a matter of debate in the past(Sodroski et al. 1989, Paladini et al. 2007, …) SPIRE 250 μm Ring 1 HI0.49 H2H H+H T(H 2 ) > T(HI) !?!

A. Traficante et al. Tor Vergata/Caltech MW /09/11 The model with no H + Without considering ionized hydrogen component the model distributes the excess in particular to the most correlated component Dust associated with ionized hydrogen was a matter of debate in the past(Sodroski et al. 1989, Paladini et al. 2007, …) SPIRE 250 μm Ring 1 HI0.49 H2H H+H T(H 2 ) > T(HI) !?!

A. Traficante et al. Tor Vergata/Caltech MW /09/11 Conclusion We have tested the inversion method taking into account the specific physical properties of a selected region of the Plane. We have modeled the dust emissivities associated to each phase of the gas (DustEM, Compiegne et al. 2010). T(H + ) > T(H 2 ) > T(HI) Indication of PAH depletion in a diffuse region of the Galactic Plane Evidence of HI and H 2 not traced with standard tracers. The analysis of the Pearson’s coefficient allows us to identify regions of absorption (cold HI). Traficante et al. 2011, in preparation

21 Alessio Traficante Tor Vergata / Caltech Analysis: molecular hydrogen Isolate the region where both 12 CO and 13 CO were observed Evaluate Tex using 12 CO map Stahler & Palla 2005 Pineda et al. 2010, Duval et al Measure 13 τ assuming 13 T ex = 12 T ex Estimate N( 13 CO) Estimate N(H 2 )

A. Traficante et al. Tor Vergata/Caltech MW /09/11 n eff diffuse(cm -3 )n eff W43 peak (cm -3 ) From the continuum ? 1. Diffuse 2. Compact HII 1.5 Gaussian Alves et al Parkes 6cm, Filipovic et al. 1995