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Lulu Fan International School for Advanced Studies (SISSA)

Herschel Galaxy Counts and High Redshift Luminosity Functions: The Formation of Massive Early Type Galaxies. Lulu Fan International School for Advanced Studies (SISSA) Center for Astrophysics, Univ. of Science and Technology of China.

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Lulu Fan International School for Advanced Studies (SISSA)

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  1. Herschel Galaxy Counts and High Redshift Luminosity Functions:The Formation of Massive Early Type Galaxies Lulu Fan International School for Advanced Studies (SISSA) Center for Astrophysics, Univ. of Science and Technology of China A. Lapi, J. Gonzalez-Nuevo, A. Bressan, G. De Zotti, L. Danese, M. Negrello April,28th,2011 Hangzhou

  2. Herschel: • launched on 14 May 2009! • 3.5 m Cassegrain telescope • photometry and spectroscopy in the 55-671 µm range • H-ATLAS: Herschel Astrophysical Terahertz Large Area Survey (Eales et al. 2010a) • ~600 hours • ~550 square degrees • both PACS and SPIRE cameras • H-ATLAS SDP data: • ~4*4 square degrees • 4851 galaxies with 250 µm fluxes >5σ(~35 mJy) and 350 µm fluxes >3σ

  3. Main purposes • FIR/sub-mm LFs and their evolutions at z>1 • Relation between SFR and halo mass • Constrain the timescale of dust-enshrouded SF in massive halos • Formation of massive ETGs at z>1

  4. Photometric Redshift : • SMM J2135-0102 (The Cosmic Eyelash) • All:three SPIRE bands(250,350,500 µm) • Part: two PACS bands(100 and 160 µm) • Similar redshift distribution • Peak at z~2 and a tail extending up to z~4 • |Δz|/(1+z) ~ 0.2

  5. LFs of high-z submm galaxies • LFs @ 100 and 250 µm (rest-frame) • 4 redshift intervals: 1~1.5;1.5~2;2~2.5;2.5~4 • 1/Vmax estimator • redshift estimates and K-corrections from SMM J2135-0102 SED • Systematic errors: Eddington bias(small,corrected using a Bayesian approach);the choice of SED(0.25 dex)

  6. LFs of high-z submm galaxies • Compared to Gruppioni et al(2010) (>70% spec-z) @ 100 µm • Compared to Eales et al(2010) (>31% spec-z) @ 250 µm • Good agreement between our LFs and theirs • LFs flatten at high luminosities! ------ the effect of strong gravitational lensing(Perrotta et al 2003;Negrello et al. 2007)

  7. LFs of high-z submm galaxies • Toy model: • Most of the star formation occurs soon after the fast collapse phase of the halo(Zhao et al. 2003) • At the redshifts (z > 1) and for the halo masses (>3*10^12M⊙) of interest here,the halo formation rate can be approximated by the positive term of the derivative with respect to the cosmic time of the cosmological mass function; • The SFR is proportional to the halo mass; • The duration Δtsfof the main star formation episode, before quenching by the AGN feedback, is roughly constant. • Full model: Granato et al. (2004) • No parameters are changed to fit the data!

  8. Timescales of UV bright,sub-mm and QSOs phase • sub-mm phase: • (consistent with the timescale inferred from the observed alpha-enhancement of massive local ETGs) • UV bright phase: (submm LFs vs. UV LFs with SFR>100 Msolar yr-1 and z~2) • QSOs phase: • assuming: the local ratio MBH/M*~0.002 already in place and Eddington rate; • compare the comoving density of massive submm galaxies with QSOs brighter than the corresponding luminosity.

  9. The Evolution of LFs • Exponential fall off • Evolve strongly up to z~2.5 • Slow down at higher z

  10. Sub-mm bright,strongly lensed galaxies • Negrello et al. 2010 Science • simple selection criteria:flux at 500um>100mJy • H-ATLAS SDP data • 5 SLGs are found • ~100% efficiency • Totally based on Granato et al.(2004) model prediction • Gonz´alez-Nuevo et al. 2011 in preparation • select based on the LFs • more complete • 25 candidates are found • >1000 SLGs are expected to be found in full H-ALTAS

  11. Submm counts • Main contributions: • Unlensed proto-spheroidal galaxies(Granato et al. 2004) • strongly lensed proto-spheroidal galaxies(Perrota et al.2003;Negrello et al. 2007) • normal and starburst galaxies(Negrello et al.2007)

  12. Conclusions • We have exploited the H-ATLAS SDP survey data to investigate the evolution of the 100 and 250 µm LFs of bright star-forming galaxies at z > 1. • The SED of SMM J2135-0102 was taken as our reference to compute the photometric redshift. • We find a significant luminosity evolution at 100µm up to z~2.5. • Our reference model(Granato et al.2004) reproduced well the 100 and 250 µm LFs and 250,350 and 500 µm counts. Evolutionary sequence in massive halos at z>1: (1) very short UV bright phase with dust-free star formation (~10^7 yr); (2) submm phase with dust-enshrouded star formation (~several 10^8 yr); (3) QSOs phase(~several 10^7 yr); (4) passive evolution towards a local ETG after QSO feedback;

  13. Thanks

  14. Photometric Redshift :Why the redshift estimates based on a single SED are sufficient for the LFs? • Three main contributions to the IR radiation: MCs,diffuse dust(cirrus) and AGN torus • (100,160 µm),250,350 and 500 µm • 1<z<3 • 50~300 µm • SFR > 100 solar mass per year • MCs components dominate

  15. Photometric Redshift :Why to take the SED of SMM J2135-0102 as the reference?

  16. Photometric Redshift :Effects on the determination of LFs with different SEDs

  17. Granato et al.(2004) model

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