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Half Full or Half Empty? Ways Forward on Massive Galaxy Evolution since z~1

Half Full or Half Empty? Ways Forward on Massive Galaxy Evolution since z~1. Daniel Eisenstein University of Arizona. Massive Galaxies from z~1. Most massive galaxies at z~0 are on the red sequence. Color bimodality at z<1 recommends the study of the buildup of the red sequence.

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Half Full or Half Empty? Ways Forward on Massive Galaxy Evolution since z~1

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  1. Half Full or Half Empty? Ways Forward on Massive Galaxy Evolution since z~1 Daniel Eisenstein University of Arizona

  2. Massive Galaxies from z~1 • Most massive galaxies at z~0 are on the red sequence. • Color bimodality at z<1 recommends the study of the buildup of the red sequence. • I'm going to talk about LF evolution a fair bit, before moving on to other items. • General theme is very large data sets.

  3. Notable evolution in the luminosity density of L* red galaxies to z=1. • A factor of 2-4 buildup in mass. • Seemingly less evolution at higher masses. Brown et al. 2006 Faber, Willmer et al. 2006

  4. AGES is a redshift survey with MMT Hectospec of the 9 deg2 NOAO Deep Wide-Field Survey Bootes field. Ic<20 for galaxies. Ic<21.5 for AGN (22.5 in parts). 20,000 redshifts. Observations complete. ~3 mag fainter than SDSS. Superb imaging NDWFS Bw, Rc, Ic to 25–26 mag. NDWFS K to 19 Vega FLAMEX J & K deeper over half the field Spitzer IRAC and MIPS (similar to SWIRE depth). Chandra (5 ksec) GALEX underway to 25 AB Radio data The AGN and Galaxy Evolution Survey (AGES)

  5. Who is AGES? • PIs: Chris Kochanek, Daniel Eisenstein, Steve Murray • Special mention: Nelson Caldwell, Richard Cool • NDWFS: Brand, Brown, Dey, R. Green, Jannuzi • Chandra: P. Green, Jones-Forman, Shields • IRAC: Brodwin, Eisenhardt, Fazio, J. Huang, Pahre, Stern • MIPS/IRS: Dole, Egami, Le Floc'h, Kuraszkiewicz, Papovich, Perez-Gonzalez, M. Rieke, Soifer, Weedman, Willmer • SO/SAO: Fan, Falco, Huchra, Impey, Moustakas, Zaritsky • GALEX: Martin, Heckman • OSU: Kollmeier, Watson

  6. Redshift Distributions • Blue: Main sample; Grey: Reweighted; Red: “Filler” sample. • Reach L* at z = 0.5. Complementary to DEEP-2, which does not target z<0.7 galaxies, save for 0.5 deg2. • At least 2000 AGN in 9 deg2. 1250 at z>1, 208 at z>2.5.

  7. Split blue vs. red galaxies, using a redshift dependent cut. • Luminosity-color bimodal distribution clearly seen at all redshifts.

  8. Red vs. Blue Galaxies • Low redshift luminosity functions match those from SDSS. • Clear evolution in both sets.

  9. Evolution of the Optical LF Preliminary • Fit Schechter forms to the LFs, holding a fixed at the SDSS values. • Luminosity density is near constant for red galaxies, increasing for blue galaxies. L* increases for both sets.

  10. Massive Galaxies in NDWFS • Brown et al. (2006) find that 4L* galaxies evolve slower than L* red galaxies. • 9 deg2 with photo-metric redshifts. Brown et al. 2006

  11. Massive Galaxies in 2SLAQ • 2dF-SDSS LRG and Quasar survey: 11k LRGs at z>0.45 over 180 deg2 observed at 2dF, color selected from SDSS imaging. • Wake et al. (2006) compares massive red galaxies at z=0.55 to those at z=0.20. • Finds evolution that is a close match (within 10%) to the predicted passive evolution. Wake et al. 2006

  12. Massive Galaxies at z=0.8 from the MMT • We used the MMT to measure redshifts of massive red galaxies at z>0.7 selected to zAB=20.3 from the SDSS deep equatorial stripe. • Compare to SDSS data at lower redshift. Preliminary Cool et al., in prep

  13. Massive Galaxies at z=0.8 from the MMT • We used the MMT to measure redshifts of massive red galaxies at z>0.7 selected to zAB=20.3 from the SDSS deep equatorial stripe. • Compare to SDSS data at lower redshift. Preliminary Cool et al., in prep

  14. Half Full or Half Empty? • In a way, it is disappointing to z<1 observers that there is so little evolution. • On the other hand, the lack of evolution is the result of strong feedback and hence is an important opportunity.

  15. Precision Measurements of LF Evolution • These galaxies are bright enough at z<1 that we will have very large surveys. • However, measuring LF evolution accurately is tricky. • At massive end, 3% in flux is 10% in number! • Galaxies are highly clustered. • Large number of photometry and definitional issues.

  16. Photometry Matters • These galaxies have extended profiles. Easy to have mismatches in the photometry across redshift. • At low z, sky subtraction can be a problem. • Note that the SDSS issues are with the pipeline photometry, not the data itself, which is very flat. • At high z, surface brightness dimming and seeing are the challenge. • We should be embracing this and measuring the luminosity function in sets of physical apertures. • If stars are being added, we'd like to know where. • Total magnitudes are not well defined anyways. • Need deep images to control these problems!

  17. K Corrections • Getting to 0.03 mag is not straight-forward. • Tilts in the overall spectrophotometric energy scale are not currently better than 1-2% per unit redshift. • Model spectra do not predict the observed colors versus redshift. • Even interpolating between filters can be trouble. Wake et al. (2006)

  18. Even if we measure the evolution in the luminosity function to a few percent, this doesn't give us the evolution of mass. "Passive evolution" doesn't predict change in luminosity to this precision. Variations in populations can probably confuse M/L at this level. These galaxies are highly clustered. Need about 108 h–3 Mpc3 to get to 3% in number density. About 100 deg2 for 0.6<z<1.0. 104-105 galaxies. This is highly feasible for both deep imaging and spectroscopy. M/L Evolution Sample Variance

  19. Red versus Blue • The color bimodality at z=0 is not total: the gap is not empty. • At high redshift, the red sequence and blue cloud move toward each other and the gap fills in. • Hard to control the definition of red and blue to a fine level. • Would this be easier with mid-UV photometry? • Should we counting massive galaxies regardless of color? Should we be studying the color distribution of massive galaxies in a continuum rather than twoclasses?

  20. LF Evolution • Reaching 10% precision or better errors on the evolution of the massive galaxy LF is possible but will require considerably more attention. • Similar in precision to next-generation SNe dark energy experiments. • Important to hear from theory what level of precision is required to distinguish interesting models. Or what precision of prediction is possible. • Ultimately, the LF is a fairly blunt tool for determining the cause of this mild evolution? What other kinds of data can we use?

  21. Small-scale Correlations • Tomorrow's mergers are today's close pairs. • By looking at galaxy correlations on small scales, we can assess the types of galaxies that are merging into a given primary type. • Requires a timescale estimate. LRG-LRG Pairs108 in x! Masjedi et al.,2006

  22. Mergers to Massive Galaxies • Masjedi et al. look at cross-correlations between SDSS LRGs and other galaxies as function of luminosity and color. • Deproject and count galaxies within 50 kpc. • Assume these will merge on a modeled time scale. • Find about 2.5% mass added per Gyr. Most mass comes from red galaxies just above L*. Masjedi et al., in prep.

  23. Cross-correlations • At small enough angles on the sky, nearly all pairs are physically associated. • Of course, one must do background subtraction, but the noise from the interlopers is sub-dominant. • This implies that one only needs one robust redshift in the pair. • Angular correlations can be converted into true spatial correlations. • There are flexible ways to do this, handling each primary galaxy separately and coadding in any binning one wants.

  24. Where is the Merging Occuring? • If galaxies can be tracked across redshift, then they flow according to the continuity equation. • This implies a particular evolution of their correlation function and HOD. • Seo et al. find that these HODs converge to an attractor that lack the usual "shoulder" of central galaxies.

  25. Environment-based Evolution & Correlations • If galaxies aren't passively evolving and we preferentially alter galaxies in a particular environment, then this will show up in the correlation functions. • Galaxy correlations are measured extremely accurately in SDSS-sized samples (<2% in s8). • The combination of weak lensing mass measurements and auto-correlations are particularly powerful. • These are very stringent tests of a galaxy model (but cosmology matters too).

  26. Spectral Modeling • We can acquire very high S/N absorption spectra of massive galaxies, including stacks of subsamples. • Can look for very subtle signatures and trends. • However, the [a/Fe] enhancement of these populations makes the modeling much harder.

  27. Pulling Apart the Red Sequence • We have mostly talked about variations in abundance, environment, spectral properties, etc, along the red sequence. • But with precision photometry one can also study gradients across the red sequence. Cool et al, 2005

  28. Feedback? • Can we find observational evidence for feedback in massive galaxies? • Correlations with radio, X-ray, environment? • Spectral signatures? • Is this a z<1 problem (for non-cluster environments)? Or is the halo gas already “fluffed up” enough at z>1? • Is the answer the same at 1013 Msun vs 1015 Msun?

  29. Conclusions • Near-term surveys will yield fabulous data for the study of massive galaxies at z<1. • Near-IR wide-field imaging, giving way to Spitzer at z~1. • New deep & wide optical imaging. • Wide-field spectroscopy. • Likely to determine LF evolution, merging, residual star formation, and halo masses to excellent precision. Set the stage for the more distinct evolution at z>1. • Trickier task is proving why z<1 star formation is truncated!

  30. Sample Variance • These galaxies are highly clustered. Need about 108 h–3 Mpc3 to get to 3% in number density. • About 100 deg2 for 0.6<z<1.0. • 104-105 galaxies. • This is highly feasible for both deep imaging and spectroscopy.

  31. AGN Target Selection • AGN were selected by X-ray, mid-IR (red in IRAC or 24 mm detect.), and radio, with limited GALEX and optical selection. • I<21.5 for point sources (I<22.5 limited coverage) • I<20 for extended sources (I<22.5 limited coverage). • At least 2000 AGN in 9 deg2. 1250 at z>1, 208 at z>2.5. • 3 AGN at 5.1<z<5.8 (Cool et al., 2006).

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