A New Photometric Technique for the Joint Selection of Star-forming and Passive Galaxies at 1.4 ≲ z ≲ 2.5

By E. Daddi, A. Cimatti, A. Renzini, A. Fontana, M. Mignoli, L. Pozzetti, P. Tozzi, G. Zamorani. 2004

566 citations recorded by the source corpus.

A simple two-color selection based on B-, z-, and K-band photometry is proposed for culling galaxies at 1.4 ≲ z ≲ 2.5 in K-selected samples and classifying them as star-forming or passive systems. The method is calibrated on the highly complete spectroscopic redshift database of the K20 survey, verified with simulations and tested on other data sets. Requiring BzK = (z - K)AB - (B - z)AB > -0.2 allows us to select actively star-forming galaxies at z ≳ 1.4, independently of their dust reddening. On the other hand, objects with BzK < -0.2 and (z - K)AB > 2.5 colors include passively evolving galaxies at z ≳ 1.4, often with spheroidal morphologies. Simple recipes to estimate the reddening, star formation rates (SFRs), and masses of BzK-selected galaxies are derived and are calibrated on K < 20 galaxies. These K < 20 galaxies have typical stellar masses of ~1011 M☉ and sky and volume densities of ~1 arcmin-2 and ~10-4 Mpc-3, respectively. Based on their UV (reddening-corrected), X-ray, and radio luminosities, the BzK-selected star-forming galaxies with K < 20 turn out to have average SFR ≈ 200 M☉ yr-1 and median reddening E(B - V) ~ 0.4. This SFR is a factor of 10 higher than that of z ~ 1 dusty extremely red objects, and a factor of 3 higher than found for z ~ 2 UV-selected galaxies, both at similar K limits. Besides missing the passively evolving galaxies, the UV selection appears to miss some relevant fraction of the z ~ 2 star-forming galaxies with K < 20, and hence of the (obscured) SFR density at this redshift. The high SFRs and masses add to other existing evidence that these z = 2 star-forming galaxies may be among the precursors of z = 0 early-type galaxies. A V/Vmax test suggests that such a population may be increasing in number density with increasing redshift. Theoretical models cannot reproduce simultaneously the space density of both passively evolving and highly star-forming galaxies at z = 2. In view of Spitzer Space Telescope observations, an analogous technique based on RJL photometry is proposed to complement the BzK selection and to identify massive galaxies at 2.5 ≲ z ≲ 4.0. By selecting passively evolving galaxies as well as actively star-forming galaxies (including strongly dust-reddened ones), these color criteria should help in completing the census of the stellar mass and of the SFR density at high redshift.

Subfields: Astronomy and Astrophysics, Instrumentation

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In Astronomy and Astrophysics

1. P. Hopkins
2. L. Hernquist
3. R. Dav'e
4. P. V. van Dokkum
5. R. Somerville
6. D. M. Alexander
7. A. Dekel
8. C. Conroy

In Instrumentation

1. P. Hopkins
2. L. Hernquist
3. P. V. van Dokkum
4. M. Franx
5. R. Dav'e
6. A. Dekel
7. C. Conroy
8. Christopher J. Conselice

Citations in the corpus

• The VIMOS VLT Deep Survey final data release: a spectroscopic sample of 35 016 galaxies and AGN out to z ~ 6.7 selected with 17.5 ≤ iAB ≤ 24.75 (2013, methodology): “…must be added to a magnitude limit, with colour-colour selection used at z ∼ 1 (e.g. DEEP2, VIPERS) or, at higher redshifts, using the BzK criterion (Daddi et al. 2004) to select populations with 1.4 < z < 2.5 (e.g. zCOSMOS-deep) or the Lyman-break technique to select populations at z > 2…”
• THE SINS SURVEY OF z ∼ 2 GALAXY KINEMATICS: PROPERTIES OF THE GIANT STAR-FORMING CLUMPS (2010, methodology): “The rest-optically-selected targets were identified based on Ksband imaging and via the “BzK” color criterion for 1.4 < z < 2.5 star-forming galaxies (Daddi et al. 2004), and followedup with VLT/VIMOS optical spectroscopy to confirm their redshift (Kong et al. 2006; Lilly et al. 2007).”
• THE LESSER ROLE OF STARBURSTS IN STAR FORMATION AT z = 2 (2011, methodology): “The datasets include in total 576 and 122 PACS-detected galaxies in the COSMOS and GOODS-South fields, respectively, and 18,981 and 586 BzK-selected (cf. Daddi et al. 2004) sources in the COSMOS and GOODS-South fields.”
• The bright end of the galaxy luminosity function at z≃7: before the onset of mass quenching? (2013, methodology): “To extract a point spread function (PSF) for each image, we selected stars using the BzK-diagram (uzK-diagram for the UltraVISTA dataset) as defined in Daddi et al. (2004).”
• COLOR–MAGNITUDE RELATIONS OF ACTIVE AND NON-ACTIVE GALAXIES IN THE CHANDRA DEEP FIELDS: HIGH-REDSHIFT CONSTRAINTS AND STELLAR-MASS SELECTION EFFECTS (2010, background): “…correlation); and (2) galaxies evolve passively (e.g., Kodama & Arimoto 1997; Stanford, Eisenhardt, & Dickinson 1998; van Dokkum & Franx 2001; Daddi et al. 2004; Bothwell, Kennicutt, & Lee 2009) or secularly (e.g., Kormendy & Kennicutt 2004; Hopkins & Hernquist 2006); this ingredient is…”
• A mature cluster with X-ray emission at z = 2.07 (2010, methodology): “…in theY-band image than in thez andB-band images, and sinceY straddles the 4000 Å break atz = 1.5, we do not rely on the traditionalBzK criterion (Daddi et al. 2004) to select for passively evolving galaxies atz > 1.5 but instead use Y − Ks > 2, the expected colour of such a galaxy population.”
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• Stellar Population Diagnostics of Elliptical Galaxy Formation (2006, background): “For the star-forming BzKselected objects, Daddi et al. (2004) estimate < SFR >≃ 200M⊙yr−1, which is typical of ULIRGs, and most of them are clearly mergers on ACS images.”
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• A large Hα survey at z = 2.23, 1.47, 0.84 and 0.40: the 11 Gyr evolution of star-forming galaxies from HiZELS (2012, background): “This colour-colour selection is a slightly modified version of the standardBzK colour-colour separation (Daddi et al. 2004)7.”
• The fourth data release of the Kilo-Degree Survey: ugri imaging and nine-band optical-IR photometry over 1000 square degrees (2019, methodology): “…for galaxies will benefit greatly from the inclusion of the near-IR fluxes (Wright et al. 2018), red-sequence cluster searches can be pushed to greater redshift, and star-galaxy separation and galaxy SED typing can be made more accurate as well (e.g., Daddi et al. 2004; Tortora et al. 2018b).”
• Rotational support of giant clumps in high-z disc galaxies (2011, background): “More than half the massive star-forming galaxies observed in the redshift rangez ∼ 1 − 3 (e.g. Steidel et al. 1999; Adelberger et al. 2004; Daddi et al. 2004) turn out to be thick, turbulent, extended, rotating discs that are highly perturbed by transient elongated features and giant clumps (Genzel…”
• Multiwavelength Study of Massive Galaxies at z~2. I. Star Formation and Galaxy Growth (2007, background): “…density of massive galaxies takes place in the cosmic time interval between z 3 and 1 (e.g., Dickinson et al. 2003; Rudnick et al. 2003, 2006; Fontana et al. 2004, 2006; Daddi et al. 2004a, hereafter D04a; van Dokkum et al. 2006; Franceschini et al. 2006; Pozzetti et al. 2007; Arnouts et al. 2007).”
• AN OBJECTIVE DEFINITION FOR THE MAIN SEQUENCE OF STAR-FORMING GALAXIES (2015, methodology): “One may select them by a slightly mass-dependent color, picking blue cloud galaxies (as in P10), or using the BzK two-color selection (Daddi et al. 2004, 2007; Pannella et al. 2009), or the rest-frame UV J selection (Whitaker et al. 2012, 2014; Williams et al. 2009), or setting a minimum threshold…”
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• The Hubble Deep Field-North SCUBA Super-map - IV. Characterizing submillimetre galaxies using deep Spitzer imaging (2006, background): “Another class of star forming galaxy at similar redshifts to the submm galaxies which has been well studied in the IR are the BzK galaxies (Daddi et al. 2004).”
• KILOPARSEC-SCALE DUST DISKS IN HIGH-REDSHIFT LUMINOUS SUBMILLIMETER GALAXIES (2016, background): “Deep (rest–frame) UV/optical surveys have yielded large samples of high–redshift (z∼1.5–3.5) star–forming galaxies selected based on magnitude/color properties (BM/BX,BzK; e.g., Steidel et al. 2004; Daddi et al. 2004, 2007a,b), the study of which has provided a basic picture of their formation.”
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• THE OPTICALLY UNBIASED GAMMA-RAY BURST HOST (TOUGH) SURVEY. I. SURVEY DESIGN AND CATALOGS (2012, background): “…Barger et al. 2000; Blain et al. 2002), Lyα emitters (LAEs; e.g., Fynbo et al. 2003b, 2005; Sawicki & Thompson 2006), distant red galaxies (DRGs; Daddi et al. 2004), damped Lyα absorbers (DLAs; Møller et al. 2002; Wolfe et al. 2005), and high-redshift dropout galaxies (e.g., Bouwens et al.…”