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Conference summary

Conference summary. Catherine Cesarsky ESO Moriond, March 2005. When UV meets infrared. (and everything from gamma rays to radio) Do we see the same sources in UV and IR?. 24 micron MIPS. GALEX. IRAC GOODS. Summary. 1. By selection, UV galaxies and IR galaxies have very different

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Conference summary

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  1. Conference summary Catherine Cesarsky ESO Moriond, March 2005

  2. When UV meets infrared • (and everything from gamma rays to radio) • Do we see the same sources in UV and IR?

  3. 24 micron MIPS GALEX IRAC GOODS

  4. Summary 1. By selection, UV galaxies and IR galaxies have very different characteristic IR/UV ratios (the means differ by a factor of 10). 2. The morphological and stellar mass distributions of the two populations have good overlaps (> 70%). IR galaxies tend to be more massive and earlier types, with an excess of interacting galaxies, and UV galaxies to be less massive and later types. 3. UV galaxies are less clustered than IR galaxies. 4. Galaxies with the highest SFR (>100 M /yr, Ltot > 1012 L ), are missed in the UV samples. 5. A population of low metallicity (< 1/10 solar), low mass (<10^9 M ) dwarf UV galaxies (prototype I Zw 18) are `IR quiet’, with the IR/UV ratio ~ 0.3 or less. They occupy only a few percent of a UV selected sample. ๏ ๏ ๏

  5. UV/mid-IR comparison of two LIRGs Images: HST/STIS UV - Contours:ISOCAM7μm 7μm/UV ~ 800:10:35 7μm/UV ~ 330:160:190 At z~2: UV --> R-/I- band & ISO/CAM 7μm -> Spitzer/MIPS24. The poor spatial at z~2 will result in blending of the emission from the unresolved interacting components. An increased scatter will thus be introduced in the observed optical to mid-IR colors of these galaxies, leading to a systematic underestimation of their dust content. Charmandaris, Le Floc’h, Mirabel, ApJ, 2004, 600, L15

  6. Do we need UV to understand star formation? • YES, at least in some cases (low obscuration)

  7. Rest UV Traces Star FormationOver Large Range of Specific Star Formation & SFR/Area Low Surface Brightness Galaxies Luminous UV Galaxies What gives??? Sgas ranges 20:1  Sgas 1.4 ranges 70:1 Early Type Gals Milky Way

  8. Shortcut to SFH Rest UV Traces Star FormationOver Large Range of Specific Star Formation • b-parameter vs. NUV-r color • Obtain b from color alone • Works when no spectra are available • Valuable for high z • Spread in x-direction due to internal extinction NUV-r  b

  9. Radial profile differences seen in other galaxies Not all galaxies show H deficit H and UV radial profilesThilker, Meuer, et al UV Ha

  10. Star clusters as indicators/ demonstrators of star formation

  11. Do we need IR to understand star formation? • YES, especially for the brightest galaxies

  12. Can the different star formation indicators be reconciled? • Sometimes…

  13. Ha/UV shows systematic trend Ha/UV in SDSSTreyer, Johnson, et al. Higher LUV, Blue NUV-r L(Ha)/L(UV)~Kennicutt Low LUV, Red NUV-r L(Ha)/L(UV) > Kennicutt

  14. SFRs as estimated by UV, [OII] & IR(Hammer et al, Venice 2003, proceedings, astro-ph/0401246) OII line & UV luminosities underestimate SFR values by factors 5 to 100 for starbursts & LIRGs !

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

  16. 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)

  17. - extinction corrected H SFRs are close to mid-IR estimates (Elbaz et al, 2002) for SFR < 150 MO/yr (i.e. below ULIRGs) •  more robust SFR estimates • luminous IR galaxies (not ULIRGs) dominates the cosmic star formation density at z~1 • (confirmed by Spitzer, Le Floch et al, 2004) •  less than 20% of the star formation density is coming from extremely dust enshrouded regions Estimating extinctions and SFRs at z ~1(Flores et al, 2004, A&A 415, 885) FORS2/ISAAC: 16 ISO galaxies, 0.4< z <1

  18. Deep IR surveys: do we understand what we see? • Probably, but…

  19. EBL: optical vs IR

  20. CIRB~ 1.5 OPT IGL In local universe, about 30% bolometric light in IR; LIRGs, ULIRGs produce 2% of bolometric luminosity However,distant universe is IR. Due to LIRGs? How distant?

  21. LW3 z=0 Typical galaxy spectra 0.5 1 1.5 2 LW3 15 LW2 6.7  K-corrections

  22. CIRB peak: 140 m Individual galaxies peak: 60 to 100 m Peak shifted to 140 m if z=0.4 to 1.3 (<z>~0.85) 15 m 8 m z=0.85  z=0 140 m 80 m ISOCAM deep surveys in LW3 (12-18 m): Ideal to detect redshifted PAH for z~0.85 (or in general at z<1.5)

  23. Number Counts • Roughly in agreement with ISOCAM results • Some confused ISOCAM sources are resolved by Spitzer • The HDF-N pilot study is not an unbiased survey • Marleau et al. (2004) find 24 mm number counts peak at fainter flux than 15 mm counts • difference b/w 15 and 24 mm counts is not the result of confusion of ISOCAM sources or systematic differences between the observatories

  24. From the MIR ? • Local universe : correlation MIR – LIR (Elbaz et al, 2002) • correlation radio-MIR (Codon 1992, Yun et al, 2001) • or radio is a tracer of LIR • MIR + local templates or correlations => FIR=> LIR => SFR • Chary & Elbaz 2001 Kennicutt 1998 • Dale & Helou, 2002 • Lagache et et al, 2004 • …….. 15 mm vs IR M82 (disque) (Laurent et al. 2000) IR vs ISOCAM 15 mm IR vs IRAS 12 mm

  25. 15mm ISOCAM 24mm Spitzer-MIPS The PAH bump exists at z=0.7 SED of a LIRG at z=0.69 (LIR~1011.1 L,SFR~22 Myr-1)

  26. LIRGs and cosmic star formation 50 % stars born z<1.5 (70 % universe age) 36 % @ z<1 (57 %) 67 % @ z<2 (76 %) W* Proportion of present-day stars born in LIRGs > 50 % ==> Common phase experienced by all/most galaxies...

  27. General 24m differential counts (this work, Chary et al. 2004, Papovich et al. 2004)

  28. Model predictions S24/S15as a function of z, S24 S > 2-3 mJy dominated by objects with S24/S152-2.5 S  0.3 mJy dominated by objects with S24/S15 1.5 S < 0.2-0.3 mJy dominated by objects with S24/S15 > 2-3 -> NEW POPULATION !

  29. R-band mag versus Flux@24μm 80% completeness limit at 24μm  VERY hard to be complete in the redshift identification at any 24μm flux, using VVDS/GOODS/COMBO-17 Rencontres de Moriond, March 6-12th 2005

  30. * Modest IR emitters at 0<z<0.5 * ULIRGs : quite rare at 0<z<1 * LIRGS: significant contribution at z>0.5 * More « normal » starbursts are not negligible neither IR luminosities in the CDFS 2635 sources with redshifts 80% completeness limit Rencontres de Moriond, March 6-12th 2005

  31. Star formation history at z<1 _ _ _ _ _ Compilation by Hopkins 2004 Lagache et al. 2004 . . . . . . Blain et al. 2002 total Chary & Elbaz 2001 11 L <10 L . IR 11 L >10 L . IR ULIRGs  LIRGs/ULIRGs dominate beyond z~0.7 Rencontres de Moriond, March 6-12th 2005

  32. Star formation history at z<1 AGN contribution ?? * ISO/XMM : <20% (Fadda et al. 2002) * X-ray +IR bkg synthetic models : <5% (e.g., Silva et al. 2004) First Spitzer results : <15% of sources flagged as AGNs by VVDS & COMBO-17 (see also SWIRE, Franceschini et al. 2005)  LIRGs/ULIRGs dominate beyond z~0.7 Rencontres de Moriond, March 6-12th 2005

  33. 3.5 * At 0<z<1, L* evolves at least by (1+z) ( exclude a pure density evolution) Summary * 55~65 % of 24μm sources at z<1 for flux>80μJy * IR luminous galaxies start to dominate the SFRH at z>0.6 * LIRGs+ULIRGs = 70% of SFR at z=1 * Need a better understanding of IR SEDs : IRS GTO, MIPS SED mode... Cornell University - Ithaca, December 1st 2004

  34. Is galaxy formation (the building up of galaxies) regular or episodic? • Mostly episodic, even if we don’t know for sure why.

  35. LIRGs: potentially double their masses in ~0.8 Gyr SFR: IR & Ha Red dots: LIRGs (20-200 MO/yr) Full squares: starbursts (<20M/yr) SFR: [OII]3727 Open symbols From BE00: Brinchman & Ellis 2000

  36. How to account for the high LIRG fraction (15% of intermediate mass galaxies) ? • A specific population ? • LIRGs are continuously forming stars during 3.3 Gyrs (z=1  z=0.4) • they would multiply their masses by 2 x (3.3/0.8)=8.2 !! • BUT no trace of recent formation of massive galaxies, dominated by E/S0, with 3 1011<Mstar<31012MO

  37. Do we understand ultra luminous star forming galaxies? • Yes, although debate on role of AGN not completely closed

  38. The first 18 low-resolution IRS spectra of ULIRGs Diversity! is the name of the game…

  39. Results of submm surveys • Highly luminous (ULIRG) systems • SFR ~ 1000 M yr-1 • Massive systems • Evidence for outflowing winds Progenitors of massive elliptical galaxies?

  40. Do we understand Luminous star forming galaxies? • Errrrr, well…

  41. Stellar properties of distant LIRGs • b parameter: SFR/<SFR> = 5 +/-3 • Burst duration ~ 108 years • Burst stellar mass fraction ~ 5-10 % • M/Lz ~ 0.3 (SDSS 1.6) • Stellar masses: <M*> ~ 5 x1010 M

  42. Large UVLGs = LIRGs ? Goldader et al. (2002) Burgarella et al. (2005) • UV Luminosity Density from UVLG x30 from z=0 to z=1 • 25% of FUV luminosity density at z=1 from UVLG • SFR from LIRGs x20 from z=0 to z=1 • > 70% of dust-enshrouded SFR density at z=1 from LIRGs

  43. Conclusions • The most UV luminous galaxies in the combined GALEX/SDSS sample comprise two populations: • Large UVLGs – rare, massive disk systems • Compact UVLGs – small systems undergoing intense star formation • Compact UVLGs appear similar in many respects to Lyman break galaxies • UV Luminosity, star formation rate (selected) • Size • UV extinction • Stellar mass, velocity dispersion • Metallicity • Compact UVLGs may be useful analogs for LBGs

  44. UV Luminous Galaxies (UVLGs)Dramatic Evolution to z=3 (DS, Ilbert, Arnouts et al) Luminosity density of UV luminous (LBG-analog) galaxies shows dramatic evolution: (1+z)5 LFUV,bol > 1010 Lsol SFR > 10 Msol/yr Steeper than QSO LD evolution (Boyle+ Madau et al) UVLGs produce a significant fraction of LD at z = 1 Total (1+z)2.5

  45. GALEX AIS + IRAS  Bivariate SF Luminosity Function LBG 1000 GALEX+IRAS galaxies LBG

  46. Do AGNs play a role in galaxy evolution? Yes.

  47. Chandra allows to separate the X-ray emission from the nucleus and the star-forming ring

  48. New GALEX data: Deep (~27 mag rms) Wide field (1.2o) FUV emission (1500A) detected: along jet(s) for >25 kpc (shocks) where jet hits cold clouds (young stars) where inner jet is disrupted (???) possibly around radio lobes (young stars?) Jet-Induced Star Formation in Centaurus AS. G. Neff et al. 5 kpc~ FUV (1500A) NUV (2300A)

  49. FUV + HI Minkowski’s Object (cf. van Breugel) Neff, Schiminovich et al.

  50. Results for 65 Sey2: for central (median) 174 pc (65 Sey 2); 121 pc (14-rest) Heterogeneous star formation histories. • 10 SSP BC03 ages, Z=1 and 2.5 solar, plus a power law FC. Some, dominated by old stars (t>2.5Ga), to 80% of the optical light; Some show strong component of intermediate age stars (100Ma<t<1.4Ga); Young clusters are ubiquitous (t<25Ma), in some cases to more than 50% of the light at 4020A and in several to 20%. Strong FC component also present. This could be a genuine monster or a dusty young burst. At least 3 of the 4 components present with significant strength (more than 10%) in any one galaxy. A simple Ell galaxy + a power law (used many times before) does not apply to the bulk of Sey 2s.

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