J. C. Muñoz Mateos, A. Gil de Paz, S. Boissier, J. Zamorano,

J. C. Muñoz Mateos, A. Gil de Paz, S. Boissier, J. Zamorano,

D. A. Dale, P. G. Pérez González, J. Gallego, B. F. Madore,

G. Bendo, M. Thornley, B. T. Draine, A. Boselli, V. Buat,

D. Calzetti, J. Moustakas & R. C. Kennicutt

MPIA, Heidelberg Feb. 22-24 2010

Radial distribution of stars, dust and

gas in the SINGS galaxies.

Correcting for internal extinction is essential to derive physical properties of galaxies: SFR Age Metallicity …

Scientific motivation


Dust is also a key ingredient in chemical evolution. Some properties correlate with metallicity: Dust-to-gas ratio PAH abundance



Dust is also a key ingredient in chemical evolution. Some properties correlate with metallicity: Dust-to-gas ratio PAH abundance

Do these trends hold at subgalactic scales?How do these properties change with radius?


The Spitzer Infrared Nearby Galaxies Survey (SINGS, Kennicutt et al. 2003) is a sample of 75 nearby galaxies, spanning all morphological types. Mid-IR data (IRAC). Far-IR data (MIPS). Optical data (ground-based).

GALEX FUV & NUV data available for 73 of them.

Additional data: HI profiles from the The HI Nearby

Galaxies Survey (THINGS, Walter et al. 2008).

CO profiles. Metallicity gradients

(Moustakas et al. 2010, in prep.)

The sample

Dust absorbs UV light and reemits it in the IR. The TIR/UV can be used to estimate the internal extinction.

It depends weakly on the dust/stars geometry, extinction curve…

young starsUV

dust

Extinction profiles

IR

young starsUV

old stars

dust



Extinction profiles

Dust heating by old stars must be taken into account (Cortese et al. 2008) IR

young starsUV

IR

old stars

dust



Dust heating by old stars must be taken into account (Cortese et al. 2008)

Extinction profiles

In starbursts, the TIR/FUV ratio is correlated with the UV slope .

In normal spirals, this relation is noisier and shifted to redder UV colors.

Using radial profiles seems to reduce the scatter.

The SFH seems to be the main cause of this shift.

The IRX- diagram

The disks of late-type spirals follow the average IRX- relation.

NGC 2403

The IRX- diagram

3.6 m5.8 m8.0 m

The bulges of early-type spirals depart from the average IRX- relation towards redder UV colours.

NGC 3031

The IRX- diagram

3.6 m5.8 m8.0 m

The outer regions of anemic spirals also move towards redder UV colours.

NGC 4826

The IRX- diagram

3.6 m5.8 m8.0 m

Dust models of Draine & Li (2007). Infrared SEDs as a function of 4 parameters: PAH abundance (qPAH). Fraction of dust mass in PDRs (). Intensity of the diffuse radiation

field (Umin). Dust mass.

NGC 7331

Physical dust models

Dust mass surface density

The dust mass surface density is highest in Sb-Sd spirals.

The profiles are roughly exponential, with central depletions in the bulges of early-type spirals (e.g. M81).

M81

Dust surface density and extinction

The same projected dust mass surface density does not always yield the same attenuation.

There is a clear lower envelope defined by Sc spirals and later.

Dust/stars geometry is likely the culprit: Dust clouds are more

porous in late-type spirals lower AFUV

Gas

Nucleosynthesis

Ejected metals Dust

Stars

Mdust/Mgas should increase with Z

Dust-to-gas ratio

Gas

Nucleosynthesis

Ejected metals Dust

Stars

Mdust/Mgas should increase with Z

Are we missing cold (<15K) dust?

Lots of gas not yet transformed into stars (and hence into dust)?

Dust-to-gas ratio

Current & future work: IFU data

PPAK & VIMOS IFU mosaics for some nearby spiral galaxies with available GALEX & Spitzer data.

To be observed as part of the Herschel Reference Sample.

2D maps of SFR, age, metallicity, extinction…

3 arcm

inCurrent & future work:

IFU data

The 7 PPAK pointings overlaid on an SDSS ugr image.

PPAK image reconstructed from the data-cube.

H

[OIII]

NGC4654

Internal extinction decreases with radius in spiral galaxies. It is larger in early-type spirals, even after removing the contribution of dust heating by old stars.

The TIR-to-FUV ratio is correlated with the slope of the UV spectrum. This allows for a rough estimation of attenuation in the lack of FIR data. Systems with quiescent SFHs depart from this relation towards redder UV colors.

Dust profiles are approximately exponential, with central depletions in bulges. The radial scale-length is roughly constant (in units of R25) from Sb’s to Sd’s.

There is a minimum attenuation for a given dust column density. This happens in Sc spirals and later, maybe implying a more porous dust geometry.

In general, the abundance of PAHs decreases with radius and is correlated with metallicity. This might have an evolutionary origin, due to PAHs being injected into the ISM over longer timescales than other dust species.

The dust-to-gas ratio decreases with radius. It is also correlated with metallicity, with a steeper slope at low metallicities, in the outer regions of late-type spirals.

Conclusions

For more information, see Muñoz-Mateos et al. 2009, ApJ, 701, 1965

Abundance of PAHs

qPAH: Fraction of the total dust mass contributed by PAHs. There is a paucity of PAHs:

in irregulars and the outer regions of late-type spirals. to a lesser extent, in early-type galaxies and bulges.

Abundance of PAHs

Dwarfirregulars

If carbon in PAHs comes mainly from AGBs, PAHs may not have had enough time to form in low-metallicity systems. Global shape (including

bending over) in agreement with some dust evolution models (Galliano et al. 2008).

But careful! Grain growth in the ISM, grain destruction…

PAHs may be selectively destroyed by UV photons in low-metallicity systems. Probably true within HII

regions (Gordon et al. 2008) or in starburst galaxies (Engelbracht et al. 2008).

J. C. Muñoz Mateos, A. Gil de Paz, S. Boissier, J. Zamorano,

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