Haojing Yan

Spitzer Observations of Massive, Red Galaxies at High Redshift*

We study massive galaxies at z ~ 1-3.5 using HST optical imaging, ground-based near-IR imaging, and Spitzer observations at 3-24 μm. From Ks-selected galaxies in the 130 arcmin2 GOODS-S field, we identify 153 distant red galaxies (DRGs) with (J - Ks)Vega ≥ 2.3. This sample is approximately complete in stellar mass for passively evolving galaxies above 1011 M☉ and z ≤ 3. Roughly half of the DRGs are objects whose optical and near-IR rest-frame light is dominated by evolved stars combined with ongoing star formation (at zmed ~ 2.5), and the others are galaxies whose light is dominated by heavily reddened (A1600 4-6 mag) starbursts (at zmed ~ 1.7). Very few DRGs (10%) have no indication of current star formation. DRGs at z ~ 1.5-3 with stellar masses ≥1011 M☉ have specific star formation rates (SFRs per unit mass) including the reradiated far-IR emission that range from 0.2 to 10 Gyr-1. Based on the X-ray luminosities and rest-frame near-IR colors, roughly one-quarter of the DRGs contain AGNs, implying that the growth of supermassive black holes coincides with the formation of massive galaxies. At 1.5 ≤ z ≤ 3, the DRGs with M ≥ 1011 M☉ have an integrated specific SFR comparable to the global value of all galaxies. In contrast, galaxies at z ~ 0.3-0.75 with M ≥ 1011 M☉ have an integrated specific SFR less than the global value and more than an order of magnitude lower than that for massive DRGs. At z 1, lower mass galaxies dominate the overall cosmic mass assembly. This suggests that the bulk of star formation in massive galaxies occurs at early cosmic epochs and is largely complete by z ~ 1.5. Further mass assembly in these galaxies takes place with low specific SFRs.

RED NUGGETS AT z ∼ 1.5: COMPACT PASSIVE GALAXIES AND THE FORMATION OF THE KORMENDY RELATION

We present the results of Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) imaging of a sample of 19 high-mass passively evolving galaxies with 1.2 < z < 2, taken primarily from the Gemini Deep Deep Survey (GDDS). Around 80% of galaxies in our GDDS sample have spectra dominated by stars with ages 1 Gyr. Our rest-frame R-band images show that most of these objects have compact regular morphologies which follow the classical R 1/4 law. These galaxies scatter along a tight sequence in the size versus surface brightness parameter space which defines the Kormendy relation. Around one-third (3/10) of the massive red objects in the GDDS sample are extraordinarily compact, with effective radii under 1 kpc. Our NICMOS observations allow the detection of such systems more robustly than is possible with optical (rest-frame UV) data, and while similar systems have been seen at z 2, this is the first time such systems have been detected in a rest-frame optical survey at 1.2 < z < 2. We refer to these compact galaxies as red nuggets, and note that similarly compact massive galaxies are completely absent in the nearby universe. We introduce a new stellar mass Kormendy relation (stellar mass density versus size) which we use to single out the effects of size evolution from those of luminosity and color evolution in stellar populations. The 1 < z < 2 passive galaxies have mass densities that are an order of magnitude larger then early-type galaxies today and are comparable to the compact distant red galaxies at 2 < z < 3. We briefly consider mechanisms for size evolution in contemporary models focusing on equal-mass mergers and adiabatic expansion driven by stellar mass loss. Neither of these mechanisms appears to be able to transform the high-redshift Kormendy relation into its local counterpart, leaving the origin and fate of these compact red nuggets unresolved.

SEDS: The Spitzer Extended Deep Survey: survey design, photometry, and deep IRAC source counts

The Spitzer Extended Deep Survey (SEDS) is a very deep infrared survey within five well-known extragalactic science fields: the UKIDSS Ultra-Deep Survey, the Extended Chandra Deep Field South, COSMOS, the Hubble Deep Field North, and the Extended Groth Strip. SEDS covers a total area of 1.46 deg(2) to a depth of 26 AB mag (3s) in both of the warm Infrared Array Camera (IRAC) bands at 3.6 and 4.5 mu m. Because of its uniform depth of coverage in so many widely-separated fields, SEDS is subject to roughly 25% smaller errors due to cosmic variance than a single-field survey of the same size. SEDS was designed to detect and characterize galaxies from intermediate to high redshifts (z = 2-7) with a built-in means of assessing the impact of cosmic variance on the individual fields. Because the full SEDS depth was accumulated in at least three separate visits to each field, typically with six- month intervals between visits, SEDS also furnishes an opportunity to assess the infrared variability of faint objects. This paper describes the SEDS survey design, processing, and publicly-available data products. Deep IRAC counts for the more than 300,000 galaxies detected by SEDS are consistent with models based on known galaxy populations. Discrete IRAC sources contribute 5.6 +/- 1.0 and 4.4 +/- 0.8 nW m(-2) sr(-1) at 3.6 and 4.5 mu m to the diffuse cosmic infrared background (CIB). IRAC sources cannot contribute more than half of the total CIB flux estimated from DIRBE data. Barring an unexpected error in the DIRBE flux estimates, half the CIB flux must therefore come from a diffuse component.

Deep wide-field spectrophotometry of the open cluster M67

We present nine color CCD intermediate-band spectrophotometry of a two square degree field centered on the old open cluster M67, from 3890

An Overdensity of Galaxies at z = 5.9 ? 0.2 in the Hubble Ultra Deep Field Confirmed Using the ACS Grism

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THE STELLAR MASSES AND STAR FORMATION HISTORIES OF GALAXIES AT z 6: CONSTRAINTS FROM SPITZER OBSERVATIONS IN THE GREAT OBSERVATORIES ORIGINS DEEP SURVEY

to nearly 1

High-Redshift Extremely Red Objects in the Hubble Space Telescope Ultra Deep Field Revealed by the GOODS Infrared Array Camera Observations

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Hubble Space Telescope Images of Submillimeter Sources: Large Irregular Galaxies at High Redshift

. These observations are taken as a part of the BATC (Beijing-Arizona-Taipei-Connecticut) Color Survey of the Sky, for both scientific and calibration reasons. With these data we show that the BATC survey can reach its goal of obtaining spectrophotometry to a zero point accuracy of 0.01 mag, and down to V = 21 with 0.3 mag random error. We fit the color-magnitude diagrams (CMDs) with Wortheys theoretical models. The net result is the excellent fit of the 4.0 Gyr, [Fe/H] =

Candidates of z 5.5-7 Galaxies in the Hubble Space Telescope Ultra Deep Field

-0.10

Red nuggets at high redshift: structural evolution of quiescent galaxies over 10 Gyr of cosmic history

model to our data, including a good fit to the main sequence (MS) turn-off. Our data are consistent with a toy model with 50\% of the stars in M67 being binaries and a random distribution of binary mass-ratios, although other models with different mass-ratio distributions cannot be ruled out. The spatial distribution and mass function (MF) of stars in M67 show marked effects of dynamical evolution and evaporation of stars from the cluster. Blue stragglers and binary stars are the most condensed within the cluster, with degree of condensation depending on mass.We find M67 to have an elongated shape, oriented at an angle of