1 / 16

A Steep Faint-End Slope of the UV LF at z~2-3: Implications for the Missing Stellar Problem

A Steep Faint-End Slope of the UV LF at z~2-3: Implications for the Missing Stellar Problem. Naveen Reddy (Hubble Fellow, NOAO). C. Steidel ( Caltech ). Galaxies in Real Life and Simulations, Leiden, Netherlands, 16 September 2008. Luminosity/Redshift Evolution of Dust;

romeo
Download Presentation

A Steep Faint-End Slope of the UV LF at z~2-3: Implications for the Missing Stellar Problem

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. A Steep Faint-End Slope of the UV LF at z~2-3: Implications for the Missing Stellar Problem Naveen Reddy (Hubble Fellow, NOAO) C. Steidel ( Caltech) Galaxies in Real Life and Simulations, Leiden, Netherlands, 16 September 2008

  2. Luminosity/Redshift Evolution of Dust; Incompleteness of Stellar Mass Density Measurements Are There Problems with Stellar Mass/ Star Formation Rate Measurements? • SFR / stellar mass calibrations • IMF evolution? • Dust extinction • Incompleteness Reddy & Steidel (2008b)

  3. Quantifying Number Densities via the UV Luminosity Function Advantages of UV: • direct tracer of massive star formation, modulo the effects of dust • deepest observations up to  2000 times more sensitive than those at IR and longer wavelengths • - accessibility over almost the entire age of the Universe Need for Spectroscopy: • assess contamination • quantify perturbing effects of line emission and consequence for sample completeness • color corrections for IGM opacity • - physical state of the ISM (stellar population; outflows)

  4. Preferential Scattering due to Lya: • contribution of high Ly EW systems at UV-faint magnitudes; ~10% (>50 A) at M ~ -17 • Change in mean dust attenuation: • - no variance with UV luminosity? • - evolution of dust with UV luminosity; UV-faint galaxies less dusty than UV-bright ones? ? Upshot: these systematics modulate the inferred faint-end slope of the UV LF by up to ~10%, with a tendency to steepen  Going Beyond the Spectroscopic Limit Use spectroscopic trends as a zeropoint for determining how galaxy properties depend on UV luminosity Reddy et al 2008a

  5. z=2: N(0.07L*<L<L*)~0.98N(>0.07L*) (0.07L*<L<L*)~0.84(>0.07L*) z=3: N(0.1L*<L<L*)~0.97N(>0.1L*) (0.1L*<L<L*)~0.82(>0.1L*) 0.1L* Advantages of our analysis • > 2000 spectroscopic redshifts at the bright-end • modeling of systematic effects • maximum-likelihood constraints on LF that are robust to non-uniform sources of scatter • - 31000 LBGs in 31 independent fields Results on the UV LF at z~2-3 0.07L* Steep faint-end slope of  ~ -1.73, similar to that measured at z~4-6 Reddy et al 2008b

  6. R<25.5 Reddy et al 2008b Make use of UGR+JK+IRAC photometry for several hundred galaxies • spectroscopic redshifts remove a key degeneracy from this analysis! • independent monochromatic indicators constrain SFRs and reddening Stellar Population Modeling

  7. Trends between UV luminosity and SFR with Stellar Mass Sawicki et al. 2007

  8. Mean Correction of ~2-3 for Total UV Luminosity Density ~4-5 dust correction ~2 dust correction Dust Corrections as a Function of UV Luminosity

  9. For >0.083L* galaxies Estimate of the Stellar Mass Function at z~2 Reddy et al 2008b

  10. Integral of the Star Formation History [L>0.083L*(z=2)] L>0.083L*(z>2)  z Integrated to L=0.083L*(z=6) What about contribution from massive galaxies?

  11. Contributions to the Stellar Mass Density at z~2 (R<25.5;<10^11 M*) ~ 3.7 +/- 0.2 crit (R>25.5;<10^11 M*) ~ 2.0 +/- 0.2 crit (>10^11 M*) ~ 1.6 +/- 0.4 crit For >0.083L* galaxies

  12. WRONG! >0.083L* Comparisons with the Integrated Star Formation History M>10^11 Msun R>25.5; M<10^11 Msun R<25.5; M<10^11 Msun

  13. Redshift Evolution of the Faint-End Slope Slope roughly constant at z>2, with  ~ -1.73 • but, strong evolution in UV LF implies sub-L* galaxies at z~6 are different from sub-L* galaxies at z~2 • - evolution of faint-end slope may have less to do with delayed feedback and more to do with the availability of low mass halos with cold gas below z~2 Reddy et al 2008b

  14. Conclusions Constraints on the faint-end slope of the UV LF: • UV LF evolves strongly between z~6 and z~2 • very steep faint-end slope of the UV LF of  ~ -1.73 at z~2 and z~3, remarkably similar to those derived at higher redshifts (z~4-6) • but, faint-end population evolves between z~6 and z~2, so evolution of faint-end slope may have less to do with feedback and more to do with the availability of low mass halos with cold gas below z~2 • dust corrections depend on how far one integrates to obtain the UV LD • Combining the stellar masses of star-forming galaxies at z~2-3 with the luminosity function: • significant stellar mass density in UV-faint galaxies (R>25.5) as in UV-bright ones • appears to resolve the supposed discrepancy between stellar mass density estimates and the integrated star formation history up to z~2

  15. ADDITIONAL SLIDES

  16. Total IR LD ~ 1.3e09 Lo/Mpc3 Total IR LD (Caputi et al. 2006) ~ 6.6e08 Lo/Mpc3 Limit of MIPS observations without prior information Infrared Luminosity Function at z~2

More Related