An Initial Look at the FIR-Radio Correlation within Galaxies using Spitzer Eric Murphy (Yale)...

An Initial Look at the FIR-Radio Correlation An Initial Look at the FIR-Radio Correlation within Galaxies using within Galaxies using SpitzerSpitzer

Eric Murphy (Yale) Eric Murphy (Yale)

Co-Investigators Co-Investigators George Helou (SSC/IPAC)George Helou (SSC/IPAC)Robert Braun (ASTRON)Robert Braun (ASTRON)Lee Armus (SSC)Lee Armus (SSC)Jeff Kenney (Yale)Jeff Kenney (Yale)SINGS teamSINGS team

Murphy et al. (2005)Murphy et al. (2005)

Eric J. Murphy Island Universes 7/7/2005

FIR – Radio CorrelationFIR – Radio Correlationq q ≡≡ log(FIR/3.75 x 10 log(FIR/3.75 x 10-12 -12 Hz/SHz/Sνν))

(Helou et al. 1985)(Helou et al. 1985)

► Spans 5 Orders of Magnitude in LuminositySpans 5 Orders of Magnitude in Luminosity► Dispersion of ~0.2 dex (no AGN, IRAS confusion Dispersion of ~0.2 dex (no AGN, IRAS confusion

etc…)etc…)► Found to Exist up to z~2 (Appleton et al. 2004)Found to Exist up to z~2 (Appleton et al. 2004)

► Thought to be driven by the Process of Massive Star Thought to be driven by the Process of Massive Star Formation (Harwit & Pacini 1975)Formation (Harwit & Pacini 1975) FIR – Dust heated by Massive starsFIR – Dust heated by Massive stars Radio – CRRadio – CRee-- accelerated by SNe in B-field accelerated by SNe in B-field

Wait a sec… How did they know before IRAS observations?Wait a sec… How did they know before IRAS observations?


The First Signs…van der Kruit 1971The First Signs…van der Kruit 1971

► ~35 years later, and still trying to figure out why it works! ~35 years later, and still trying to figure out why it works!

But…But…► FIR affected by:FIR affected by:

IMFIMF UV photon transportUV photon transport Optical depthOptical depth Grain distribution/compositionGrain distribution/composition

► Radio affected by:Radio affected by: IMFIMF SNe & SNRSNe & SNR ISM shocksISM shocks Particle accelerationParticle acceleration Transport – diffusion & Transport – diffusion &

confinementconfinement Magnetic FieldMagnetic Field

► How can FIR/Radio ratios of How can FIR/Radio ratios of galaxies show such little galaxies show such little scatter?scatter?

Duric (1991)


IR and Radio DataIR and Radio Data

► SpitzerSpitzer IR data: IR data: MIPS maps at MIPS maps at 2424, , 7070, and 160, and 160μμmm

►FWHM of 70FWHM of 70μμm PSF ~17”m PSF ~17”

► WSRT Radio Continuum data:WSRT Radio Continuum data: Maps at 18 and Maps at 18 and 2222cmcm

►FWHM of radio beam ~17”FWHM of radio beam ~17”►CLEAN data restored with MIPS 70CLEAN data restored with MIPS 70μμm PSFm PSF

► Galaxy Sample: 30 galaxy subset of SINGS Legacy Galaxy Sample: 30 galaxy subset of SINGS Legacy Science Sample (Kennicutt et al. 2003)Science Sample (Kennicutt et al. 2003)

SINGS


Thesis GoalsThesis Goals

► Improve the current physical picture of the FIR-Radio Improve the current physical picture of the FIR-Radio correlation:correlation: Quantify variations in the correlation across galaxy disks.Quantify variations in the correlation across galaxy disks. Correlate observed variations with ancillary observations.Correlate observed variations with ancillary observations.

► e.g. mean star-formation age and strengthe.g. mean star-formation age and strength

Derive a better understanding of what regulates the Derive a better understanding of what regulates the correlation on galaxy scales.correlation on galaxy scales.

► Constrain CRConstrain CRee-- diffusion and decay models from diffusion and decay models from observations.observations.


Paper Sample GalaxiesPaper Sample Galaxies►Chosen due to proximity and low inclination.Chosen due to proximity and low inclination.

GalaxyGalaxy TypeType DistanceDistance

(Mpc)(Mpc)

ResolutionResolution

(pc)(pc)

SFRSFR

(M(M/yr)/yr)

qq

NGC 2403NGC 2403 SABcdSABcd 3.53.5 300300 0.7720.772 2.502.50

NGC 3031NGC 3031 SAabSAab 3.53.5 300300 0.8570.857 2.452.45

NGC 5194NGC 5194 SABbcSABbc 8.28.2 750750 6.066.06 2.092.09

NGC 6946NGC 6946 SABcdSABcd 5.55.5 500500 4.054.05 2.282.28

SFRs are IRAS based using equation 5 from Bell (2003)

NGC 2403NGC 2403 NGC 3031NGC 3031 NGC 5194NGC 5194 NGC 6946NGC 6946

II2424µmµm

II7070µmµm

II2222cmcm


IR/Radio (q) MapsIR/Radio (q) Maps

qqλλ log(f log(fνν((λλ[[μμm])/fm])/fνν(22cm)) (22cm))

►λλ=24 and 70µm=24 and 70µm At best common resolution w/ radio dataAt best common resolution w/ radio data

qq7070 Maps Maps

qq2424 Maps Maps


qqλλ Map Results Map Results

Coincidence in IR and Radio PeaksCoincidence in IR and Radio Peaksqq2424 more strongly peaked than q more strongly peaked than q7070 around HII regions around HII regions

24µm emission traces hotter dust & more localized around 24µm emission traces hotter dust & more localized around HII regionsHII regions

IR/Radio MorphologyIR/Radio MorphologyHigher along Arms & HII regionsHigher along Arms & HII regionsLower for inter-arms & outer-diskLower for inter-arms & outer-disk

Aperture PhotometryAperture Photometry

► ‘‘Critical’ Aperture SizeCritical’ Aperture Size FWHM of 70FWHM of 70μμm PSFm PSF Linearly Projected at:Linearly Projected at:

NGC 5194 0.75 kpc NGC 6946 0.5 kpcNGC 5194 0.75 kpc NGC 6946 0.5 kpcNGC 3031 0.3 kpc NGC 2403 0.3 kpcNGC 3031 0.3 kpc NGC 2403 0.3 kpc

► RegionsRegions Nucleus: CyanNucleus: Cyan Inner-Disk: RedInner-Disk: Red Arm: BlueArm: Blue Inter-Arm: GreenInter-Arm: Green Outer-Disk: YellowOuter-Disk: Yellow

Radial Trends in qRadial Trends in q7070

qq7070 vs. f vs. fνν(70(70μμmm))

qq70 70 withinwithin and and amongamong Galaxies Galaxies(1.5 kpc apertures)(1.5 kpc apertures)

σg = 0.267N = 1752(Yun et al. 2002)

σw= 0.240N = 282


Aperture Photometry ResultsAperture Photometry ResultsGeneral trend of increasing qGeneral trend of increasing q70 70 and qand q2424 with: with: Increasing IR surface brightness (Opposite of global trend)Increasing IR surface brightness (Opposite of global trend) Decreasing RadiusDecreasing Radius

Dispersion at constant radius ~25% larger than at Dispersion at constant radius ~25% larger than at constant surface brightness.constant surface brightness. SF sites more important in determining shape of IR/radio disk SF sites more important in determining shape of IR/radio disk

than exponential disks.than exponential disks.

Dispersion in qDispersion in q7070 withinwithin galaxies comparable to galaxies comparable to

dispersion dispersion amongamong galaxies galaxies


Cosmic Ray Diffusion ModelingCosmic Ray Diffusion Modeling

►Image Smearing Model of Bicay & Helou Image Smearing Model of Bicay & Helou (1990)(1990)

►Assumption: Difference in IR and Radio Assumption: Difference in IR and Radio morphology due to diffusion of CRmorphology due to diffusion of CRee--

►Following work of Marsh & Helou (1995, 98)Following work of Marsh & Helou (1995, 98) But, we are using IR images at native resolution But, we are using IR images at native resolution

(unlike IRAS HiRes used by MH95, 98)(unlike IRAS HiRes used by MH95, 98)

Residuals vs. Scale-lengthResiduals vs. Scale-length


CRCRee-- Diffusion Modeling Results Diffusion Modeling ResultsSmearing technique works to improve the correlationSmearing technique works to improve the correlation Reduces residuals by up to a factor of 2Reduces residuals by up to a factor of 2

Exponential kernels work marginally better than Exponential kernels work marginally better than Gaussians (~15%)Gaussians (~15%) Suggests CRSuggests CRee-- evolution not well described by random-walk evolution not well described by random-walk

diffusiondiffusion

A single kernel does not work for entire disk.A single kernel does not work for entire disk. Residual trends opposite for active & quiescent regionsResidual trends opposite for active & quiescent regions

Quiescent galaxies have larger scale-lengthsQuiescent galaxies have larger scale-lengths Due to deficit of recent CRDue to deficit of recent CRee-- injection into ISM injection into ISM

NGC 2403: Are we seeing two populations of CRNGC 2403: Are we seeing two populations of CRee--??

NGC 2403: NGC 2403: A case for 2 CRA case for 2 CRee-- populations? populations?

n ≥ 5 cm-3

l ~ 1 kpcτ ~ 5 x 107 yrs

(Helou & Bicay (1993)

NGC 6946:l = 300 pc

NGC 2403:l1= ~200 pc l2= ~1 kpc


Future GoalsFuture Goals► Perform same analysis on ~30 SINGS galaxies.Perform same analysis on ~30 SINGS galaxies.

► More Detailed Modeling of CRMore Detailed Modeling of CRee-- Diffusion Diffusion Separate high spatial frequency components from disksSeparate high spatial frequency components from disks Compare observed smearing scale-lengths with models Compare observed smearing scale-lengths with models

► Include other data sets to Include other data sets to help constrain dependence of IR/radio ratio on HII region age and ISM help constrain dependence of IR/radio ratio on HII region age and ISM

properties.properties. gain more insight into CRgain more insight into CRee-- physics: physics:

► NIR [FeII] and PaNIR [FeII] and Paββ imaging imaging► Dust Temperature MapsDust Temperature Maps► Radio spectral index mapsRadio spectral index maps► 8/248/24μμm colorsm colors► IRS SpectroscopyIRS Spectroscopy

An Initial Look at the FIR-Radio Correlation within Galaxies using Spitzer Eric Murphy (Yale)...

Documents

Transcript of An Initial Look at the FIR-Radio Correlation within Galaxies using Spitzer Eric Murphy (Yale)...