Optical and near-IR spectroscopy of candidate red galaxies in two <i>z</i> ~ 2.5 proto-clusters

Doherty, Michelle; Tanaka, Masayuki; Breuck, C. De; Ly, Chun; Kodama, Tadayuki; Kurk, J.; Seymour, N.; Vernet, J.; Stern, Daniel; Venemans, Bram; Kajisawa, Masaru; Tanaka, Ichi

doi:10.1051/0004-6361/200912868

Cited by 58 publications

(74 citation statements)

References 43 publications

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“…As pointed out by Doherty et al (2009), the J and K s band photometric zero-points used in Kodama et al (2007) were off by ∼0.3 mag. We re-measured the zero points from the standard stars observed in the same nights and adopted those revised zero points.…”

Section: Pks1138mentioning

confidence: 80%

“…We adopt the Salpeter initial mass function 1 (Salpeter 1955) to keep consistency with our previous study (Doherty et al 2009) and solar and sub-solar metallicities (Z = 0.02 and 0.008). The physical parameters that go into the templates are:…”

Section: Model Templatesmentioning

confidence: 99%

“…The crosses show objects with χ 2 ν > 3 both for PKS1138 and GOODS. Croft et al (2005), and Doherty et al (2009) and those in GOODS are from the GOODS-MUSIC catalog (Grazian et al 2006 and references therein). The correlation is reasonably good, although there are a number of galaxies with wrong photo-z.…”

Section: Photometric Redshiftsmentioning

confidence: 99%

“…In fact, Zirm et al (2008) reported on the forming cluster red sequence. Recently, Doherty et al (2009) carried out a near-IR spectroscopic follow-up observation and confirmed two massive red galaxies at the cluster redshift.…”

Section: Introductionmentioning

confidence: 99%

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The environmental dependence of galaxy properties atz = 2

Tanaka¹,

Breuck²,

Venemans³

et al. 2010

A&A

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We report on the environmental dependence of galaxy properties at z = 2.15. We construct multi-band photometric data sets in the (proto-)cluster PKS1138-26 field and in the GOODS field. We then fit spectral energy distributions of the galaxies with model templates generated with the latest stellar population synthesis code and derive physical properties of galaxies from the fits. To quantify the environmental dependence of galaxy properties, a special care is taken of systematic errors -we use data sets that have almost the same wavelength samplings, use the same code to fit SEDs with the same set of templates, and compare relative differences between the two samples. We find that the PKS1138 galaxies have similar ages, shorter star formation time scales, lower star formation rates, and weaker dust extinction compared to the GOODS galaxies at z ∼ 2. This trend is similar to that observed locally, suggesting that the environmental dependence of galaxy properties is already partly in place as early as z = 2.15. We show that the PKS1138 galaxies assemble the bulk of their masses ∼1 Gyr earlier than field galaxies, i.e., the galaxy formation depends on environment. Galaxy mergers should frequently occur during the first collapse of clusters and they might play an important role in driving the observed environmental dependence of galaxy properties at z = 2.15.

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Section: Pks1138mentioning

confidence: 80%

Section: Model Templatesmentioning

confidence: 99%

Section: Photometric Redshiftsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The environmental dependence of galaxy properties atz = 2

Tanaka¹,

Breuck²,

Venemans³

et al. 2010

A&A

Self Cite

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“…A complementary approach is to isolate the evolved, massive galaxy population near HzRGs using purely near-infrared colour selection (Kajisawa et al 2006;Kodama et al 2007). Though this method has successfully found overdensities of red galaxies at z ∼ 2, it has been challenging to spectroscopically confirm their association with the HzRGs (e.g., Doherty et al 2010). A few studies have also applied related methods to slightly lower redshift HzRGs -e.g., Stern et al (2003) and Best et al (2003) found overdensities of extremely red galaxies in the environments of radio-loud active galactic nuclei (AGN) at z ∼ 1.5.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic confirmation of a galaxy cluster associated with 7C 1756+6520 atz= 1.416

Galametz

Stern

Stanford

et al. 2010

A&A

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We present spectroscopic follow-up of an overdensity of galaxies photometrically selected to be at 1.4 < z < 2.5 found in the vicinity of the radio galaxy 7C 1756+6520 at z = 1.4156. Using the DEIMOS optical multi-object spectrograph on the Keck 2 telescope, we observed a total of 129 BzK-selected sources, comprising 82 blue, star-forming galaxy candidates (sBzK) and 47 red, passivelyevolving galaxy candidates (pBzK*), as well as 11 mid-infrared selected AGN candidates. We obtain robust spectroscopic redshifts for 36 blue galaxies, 7 red galaxies and 9 AGN candidates. Assuming all foreground interlopers were identified, we find that only 16% (9%) of the sBzK (pBzK*) galaxies are at z < 1.4. Therefore, the BzK criteria are shown to be relatively robust at identifying galaxies at moderate redshifts. Twenty-one galaxies, including the radio galaxy, four additional AGN candidates and three red galaxy candidates are found with 1.4156 ± 0.025, forming a large scale structure at the redshift of the radio galaxy. Of these, eight have projected offsets <2 Mpc relative to the radio galaxy position and have velocity offsets <1000 km s −1 relative to the radio galaxy redshift. This confirms that 7C 1756+6520 is associated with a high-redshift galaxy cluster. A second compact group of four galaxies is found at z ∼ 1.437, forming a sub-group offset by Δv ∼ 3000 km s −1 and approximately 1. 5 east of the radio galaxy.

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Radio Studies of Galaxy Formation: Dense Gas History of the Universe

Carilli

Walter

Riechers

et al. 2011

Reviews in Modern Astronomy

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Deep optical and near-IR surveys have traced the star formation history of the Universe as a function of environment, stellar mass, and galaxy activity (AGN and star formation), back to cosmic reionization and the first galaxies (z ∼ 6 to 8). While progress has been truly impressive, optical and near-IR studies of primeval galaxies are fundamentally limited in two ways: (i) obscuration by dust can be substantial for rest-frame UV emission, and (ii) near-IR studies reveal only the stars and ionized gas, thereby missing the evolution of the cool gas in galaxies, the fuel for star formation. Line and continuum studies at centimeter through submillimeter wavelengths address both these issues, by probing deep into the earliest, most active and dust obscured phases of galaxy formation, and by revealing the molecular and cool atomic gas. We summarize the techniques of radio astronomy to perform these studies, then review the progress on radio studies of galaxy formation. The dominant work over the last decade has focused on massive, luminous starburst galaxies (submm galaxies and AGN host galaxies). The far infrared luminosities are ∼ 10 13 L ⊙ , implying star formation rates, SFR ≥ 10 3 M ⊙ year −1 . Molecular gas reservoirs are found with masses: M(H 2 ) > 10 10 (α/0.8) M ⊙ . The CO excitation in these luminous systems is much higher than in low redshift spiral galaxies. Imaging of the gas distribution and dynamics suggests strongly interacting and merging galaxies, indicating gravitationally induced, short duration (≤ 10 7 year) starbursts. These systems correspond to a major star formation episode in massive ⋆ The Very Large Array of the National Radio Astronomy Observatory, is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc -2 -galaxies in proto-clusters at intermediate to high redshift. Recently, radio observations have probed the more typical star forming galaxy population (SFR ∼ 10 2 M ⊙ year −1 ), during the peak epoch of Universal star formation (z ∼ 1.5 to 2.5). These observations reveal massive gas reservoirs without hyper-starbursts, and show that active star formation occurs over a wide range in galaxy stellar mass. The conditions in this gas are comparable to those found in the Milky Way disk. A key result is that the peak epoch of star formation in the Universe also corresponds to an epoch when the baryon content of star forming galaxies was dominated by molecular gas, not stars. We consider the possibility of tracing out the dense gas history of the Universe, and perform initial, admittedly gross, calculations. We conclude with a description and status report of the Atacama Large Millimeter Array, and the Expanded Very Large Array. These telescopes represent an order of magnitude, or more, improvement over existing observational capabilities from 1 GHz to 1 THz, promising to revolutionize our understanding of galaxy formation.

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Optical and near-IR spectroscopy of candidate red galaxies in two z ~ 2.5 proto-clusters

Cited by 58 publications

References 43 publications

The environmental dependence of galaxy properties atz = 2

The environmental dependence of galaxy properties atz = 2

Spectroscopic confirmation of a galaxy cluster associated with 7C 1756+6520 atz= 1.416

Radio Studies of Galaxy Formation: Dense Gas History of the Universe

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