UV and FIR properties of galaxies UV and FIR properties of galaxies from combinedfrom combined GALEXGALEX--IRASIRAS datadata

Jorge Iglesias PáramoJorge Iglesias PáramoV. BuatV. Buat

T. TakeuchiT. TakeuchiK. XuK. Xu

& the GALEX team& the GALEX team

MotivationMotivation

● To understand the differential properties and To understand the differential properties and observational biases of UV and FIR selections.observational biases of UV and FIR selections.

● To consistently calibrate physical quantities To consistently calibrate physical quantities estimated from the samples.estimated from the samples.

● To provide observables for models of statistical To provide observables for models of statistical properties of galaxies.properties of galaxies.

The dataThe data

NUV selected sampleNUV selected sample: from GALEX AIS (615 : from GALEX AIS (615 degdeg22).).● mmNUVNUV < 16 ABmag < 16 ABmag● FIR counterparts from IRAS FSC (SCANPI)FIR counterparts from IRAS FSC (SCANPI)● Detection at 60µm of all galaxies with ADetection at 60µm of all galaxies with A

NUVNUV > >

0.3 mag0.3 mag94 galaxies94 galaxiesFIR selected sampleFIR selected sample: from IRAS PSCz (509 : from IRAS PSCz (509

degdeg22).).● ff6060 > 0.6 Jy > 0.6 Jy● UV counterparts from GALEX AISUV counterparts from GALEX AIS● Detection at NUV of all galaxies with ADetection at NUV of all galaxies with A

NUVNUV < 4.4 < 4.4

magmag163 galaxies163 galaxies

IRAS PSCz

IRAS FSC

GALEX AIS mNUV=16

FFNUVNUV vs. F vs. F6060µµmm

log F

60 (

erg

s-1 c

m-2)

log FNUV (erg s-1 cm-2)

The FIR selected sample is drawn from a larger The FIR selected sample is drawn from a larger volume than the NUV selected one.volume than the NUV selected one.

Vel. (km s-1)

Representativity of the SamplesRepresentativity of the Samples

Takeuchi et al. (2003)

Wyder et al. (2005)

UV and FIR luminositiesUV and FIR luminosities

log L

NU

V (

L su

n)

log L60 (Lsun)

NVSSNVSSNVSSNVSS

NUVNUV IRAS 60µIRAS 60µ

In order to improve the quality of the FIR/UV flux In order to improve the quality of the FIR/UV flux association some objets of both samples were association some objets of both samples were discarded...discarded...

NUVNUV IRAS 60µIRAS 60µ

Also discarded for the FIR/UV analysis:Also discarded for the FIR/UV analysis:

● Ellipticals and S0sEllipticals and S0s

● AGNsAGNs

● Galaxies for which Cirrus > 2Galaxies for which Cirrus > 2

Finally we end up with:Finally we end up with:

● NUV selected subsampleNUV selected subsample: : 62 62

galaxiesgalaxies

● FIR selected subsampleFIR selected subsample: : 118 118

galaxiesgalaxies

Dust attenuationDust attenuation

⟨ANUV⟩ ~ 0.8 mag⟨ANUV⟩ ~ 2.1 mag

AANUVNUV directly from F directly from FFIRFIR/F/FNUVNUV (Buat et al. 2005) (Buat et al. 2005)

ANUV (mag)

AANUVNUV correlated correlated with Lwith LHH for NUV for NUV selected selected galaxies.galaxies.

No such No such relation is relation is observed for observed for the FIR the FIR selected selected galaxies.galaxies. log LH (Lsun)

AN

UV (

mag

)

Star Formation RatesStar Formation Rates

Scenario:Scenario:

● Constant SFR over the last 10Constant SFR over the last 1088 yr yr

● Salpeter IMF with 0.1MSalpeter IMF with 0.1M⊙⊙ < M< M✮✮ < 100M < 100M⊙⊙

● Solar metallicitySolar metallicity

From Starburst99:From Starburst99:

● log SFRlog SFRNUVNUV (M (M⊙⊙ yr yr-1-1) = log L) = log L

NUV,corrNUV,corr (L (L⊙⊙) – 9.33) – 9.33

● log SFRlog SFRdustdust (M (M⊙⊙ yr yr-1-1) = log L) = log L

dustdust (L (L⊙⊙) - 9.75) - 9.75

Comparison between SFRComparison between SFRNUVNUV and SFR and SFRdustdust

SFRSFRNUVNUV vs. SFR vs. SFR

dustdust

Quite good agreement on average but...Quite good agreement on average but...lo

g S

FRd

ust (

Msu

n y

r-1)

log SFRNUV (Msun yr-1)

● At low values of At low values of AANUVNUV, the dust , the dust

emission emission underestimates the underestimates the total SFR because of total SFR because of the non negligible the non negligible NUV emission.NUV emission.● At high values of At high values of AANUVNUV, the NUV , the NUV

emission emission underestimates the underestimates the total SFR. total SFR. Problem with AProblem with ANUVNUV??

Two different trends are observed:Two different trends are observed:

log SFRNUV (Msun yr-1)

log S

FRN

UV/S

FRd

ust

Star Formation Activity: FStar Formation Activity: F60µm60µm/F/F100µm100µm

log F60/F100

Birthrate parameterBirthrate parameter

b = SFRb = SFR00/ SFR⟨ ⟩/ SFR⟨ ⟩

We obtain values We obtain values typical of Sb - Sbc typical of Sb - Sbc galaxies galaxies (Kennicutt et al. (Kennicutt et al. 1994).1994).

Following Boselli Following Boselli et al. (2001):et al. (2001):

b b ∝∝ SFR SFRNUVNUV/L/LHH

log blog b

FFdustdust/F/FFUVFUV vs. vs. ββ

● To the left of To the left of the starburst the starburst sequence of sequence of Meurer et al. Meurer et al. (1995).(1995).

Starbursts

● The distance to The distance to the sequence is the sequence is not related to the not related to the birthrate birthrate parameter.parameter.

log F

du

st/F

FUV

beta

FFdustdust/F/FFUVFUV vs. vs. ββ

● Some of them Some of them follow the same follow the same trend as the NUV trend as the NUV selected.selected.

Starbursts

● The rest, to the The rest, to the left of the left of the starburst starburst sequence, below sequence, below the ULIRGS of the ULIRGS of (Goldader et al. (Goldader et al. 2002).2002).

log F

du

st/F

FUV

beta

Meurer et al. (1999)

SFR per unit areaSFR per unit area

Lower than local starbursts for both samples.Lower than local starbursts for both samples.

log SFRNUV (Msun yr-1)log S

FRN

UV/A

rea (

Msu

n y

r-1 k

pc-

2)

The SFRThe SFRNUVNUV vs. SFR vs. SFRdustdust discrepancy is mainly discrepancy is mainly

related to the star formation activity.related to the star formation activity.

log SFRNUV/Area (Msun yr-1 kpc-2)

log S

FRN

UV/S

FRd

ust

StarbursStarburstt

Normal SFNormal SF

UV Structural PropertiesUV Structural Properties

Concentration index: 5 Concentration index: 5 ×× log r log r8080/r/r2020

Concentration index

No obvious correlation between concentration No obvious correlation between concentration index and morphological type.index and morphological type.

Different morphological patterns...Different morphological patterns...

UV Bright GalaxiesUV Bright Galaxies● We find 8 galaxies with LWe find 8 galaxies with L

FUVFUV ≥ 2 ≥ 2 ×× 10 101010 L L⊙⊙, , all of all of

them FIR selected and 3 also NUV selected.them FIR selected and 3 also NUV selected.

● Co-moving spatial density: ~ 5.3 Co-moving spatial density: ~ 5.3 ±± 3.1 3.1 ×× 10 10-6-6 MpcMpc-3-3

● Redshift range: z < 0.10Redshift range: z < 0.10

● Dust attenuation: 1.3 < ADust attenuation: 1.3 < AFUVFUV < 3.5 mag < 3.5 mag

● Low surface brightness: Low surface brightness: ∑∑FUVFUV < 1.32 < 1.32 ×× 10 1088 L L⊙⊙

kpckpc-2-2

● For all of them: LFor all of them: L6060µmµm > L > L

FUVFUV ⇒⇒ Very luminous Very luminous

objects!objects!