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UV and FIR properties of galaxies from combined GALEX - IRAS data

UV and FIR properties of galaxies from combined GALEX - IRAS data. Jorge Iglesias Páramo V. Buat T. Takeuchi K. Xu & the GALEX team. Motivation. To understand the differential properties and observational biases of UV and FIR selections.

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UV and FIR properties of galaxies from combined GALEX - IRAS data

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  1. UV and FIR properties of galaxies from combinedGALEX-IRASdata Jorge Iglesias Páramo V. Buat T. Takeuchi K. Xu & the GALEX team

  2. Motivation • To understand the differential properties and observational biases of UV and FIR selections. • To consistently calibrate physical quantities estimated from the samples. • To provide observables for models of statistical properties of galaxies.

  3. The data NUV selected sample: from GALEX AIS (615 deg2). • mNUV < 16 ABmag • FIR counterparts from IRAS FSC (SCANPI) • Detection at 60µm of all galaxies with ANUV > 0.3 mag 94 galaxies FIR selected sample: from IRAS PSCz (509 deg2). • f60 > 0.6 Jy • UV counterparts from GALEX AIS • Detection at NUV of all galaxies with ANUV < 4.4 mag 163 galaxies

  4. mNUV=16 GALEX AIS IRAS PSCz IRAS FSC FNUV vs. F60µm log F60 (erg s-1 cm-2) log FNUV (erg s-1 cm-2)

  5. The FIR selected sample is drawn from a larger volume than the NUV selected one. Vel. (km s-1)

  6. Wyder et al. (2005) Takeuchi et al. (2003) Representativity of the Samples

  7. UV and FIR luminosities log LNUV (Lsun) log L60 (Lsun)

  8. IRAS 60µ IRAS 60µ NUV NUV NVSS NVSS In order to improve the quality of the FIR/UV flux association some objets of both samples were discarded...

  9. Also discarded for the FIR/UV analysis: • Ellipticals and S0s • AGNs • Galaxies for which Cirrus > 2 Finally we end up with: • NUV selected subsample: 62 galaxies • FIR selected subsample: 118 galaxies

  10. Dust attenuation ANUV directly from FFIR/FNUV (Buat et al. 2005) 〈ANUV〉 ~ 0.8 mag 〈ANUV〉 ~ 2.1 mag ANUV (mag)

  11. ANUV correlated with LH for NUV selected galaxies. ANUV (mag) No such relation is observed for the FIR selected galaxies. log LH (Lsun)

  12. Star Formation Rates Comparison between SFRNUV and SFRdust Scenario: • Constant SFR over the last 108 yr • Salpeter IMF with 0.1M⊙< M✮ < 100M⊙ • Solar metallicity From Starburst99: • log SFRNUV (M⊙ yr-1) = log LNUV,corr (L⊙) – 9.33 • log SFRdust (M⊙ yr-1) = log Ldust (L⊙) - 9.75

  13. SFRNUV vs. SFRdust Quite good agreement on average but... log SFRdust (Msun yr-1) log SFRNUV (Msun yr-1)

  14. Two different trends are observed: • At low values of ANUV, the dust emission underestimates the total SFR because of the non negligible NUV emission. log SFRNUV/SFRdust • At high values of ANUV, the NUV emission underestimates the total SFR. Problem with ANUV? log SFRNUV (Msun yr-1)

  15. Star Formation Activity: F60µm/F100µm log F60/F100

  16. Birthrate parameter Following Boselli et al. (2001): b ∝ SFRNUV/LH b = SFR0/〈SFR〉 We obtain values typical of Sb - Sbc galaxies (Kennicutt et al. 1994). log b

  17. Starbursts Fdust/FFUV vs. β • To the left of the starburst sequence of Meurer et al. (1995). log Fdust/FFUV • The distance to the sequence is not related to the birthrate parameter. beta

  18. Starbursts Fdust/FFUV vs. β • Some of them follow the same trend as the NUV selected. log Fdust/FFUV • The rest, to the left of the starburst sequence, below the ULIRGS of (Goldader et al. 2002). beta

  19. Meurer et al. (1999) SFR per unit area Lower than local starbursts for both samples. log SFRNUV/Area (Msun yr-1 kpc-2) log SFRNUV (Msun yr-1)

  20. The SFRNUV vs. SFRdust discrepancy is mainly related to the star formation activity. log SFRNUV/SFRdust log SFRNUV/Area (Msun yr-1 kpc-2)

  21. Starburst Normal SF

  22. UV Structural Properties Concentration index: 5 × log r80/r20 Concentration index

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

  24. Different morphological patterns...

  25. UV Bright Galaxies • We find 8 galaxies with LFUV ≥ 2 × 1010 L⊙, all of them FIR selected and 3 also NUV selected. • Redshift range: z < 0.10 • Co-moving spatial density: ~ 5.3 ± 3.1 × 10-6 Mpc-3 • Dust attenuation: 1.3 < AFUV < 3.5 mag • Low surface brightness: ∑FUV < 1.32 × 108 L⊙ kpc-2 • For all of them: L60µm > LFUV⇒Very luminous objects!

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