A Survey of Star-forming Galaxies in the 1.4 ≲ z ≲ 2.5 Redshift Desert: Overview

By C. Steidel, A. Shapley, M. Pettini, K. Adelberger, D. Erb, Naveen A. Reddy, M. Hunt. 2004

503 citations recorded by the source corpus.

The redshift interval 1.4 ≲ z ≲ 2.5 has been described by some as the "redshift desert" because of historical difficulties in spectroscopically identifying galaxies in that range. In fact, galaxies can be found in large numbers with standard broadband color selection techniques coupled with follow-up spectroscopy with UV and blue-sensitive spectrographs. In this paper we present the first results of a large-scale survey of such objects, carried out with the blue channel of the LRIS spectrograph (LRIS-B) on the Keck I Telescope. We introduce two samples of star-forming galaxies, "BX" galaxies at ⟨z⟩ = 2.20 ± 0.32 and "BM" galaxies at ⟨z⟩ = 1.70 ± 0.34. In seven survey fields we have spectroscopically confirmed 749 of the former and 114 of the latter. Interlopers (defined as objects at z < 1) account for less than 10% of the photometric candidates, and the fraction of faint active galactic nuclei is ~3% in the combined BX/BM sample. Deep near-IR photometry of a subset of the BX sample indicates that, compared with a sample of similarly UV-selected galaxies at z ~ 3, the z ~ 2 galaxies are on average significantly redder in (ℛ-Ks), indicating longer star formation histories, increased reddening by dust, or both. Using near-IR Hα spectra of a subset of BX/BM galaxies to define the galaxies' systemic redshifts, we show that the galactic-scale winds that are a feature of star-forming galaxies at z ~ 3 are also common at later epochs and have similar bulk outflow speeds of 200-300 km s-1. We illustrate with examples the information that can be deduced on the stellar populations, metallicities, and kinematics of redshift desert galaxies from easily accessible rest-frame far-UV and rest-frame optical spectra. Far from being hostile to observations, the universe at z ~ 2 is uniquely suited to providing information on the astrophysics of star-forming galaxies and the intergalactic medium, and the relationship between the two.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

• The Stellar Mass Assembly of Galaxies from z = 0 to z = 4: Analysis of a Sample Selected in the Rest-Frame Near-Infrared with Spitzer (2007, methodology): “We identified LBGs following Steidel et al. (2003) and Steidel et al. (2004), which establish the locus of LBGs in a Un − G vs.”
• Nebular Emission Line Ratios in z ≃ 2–3 Star-forming Galaxies with KBSS-MOSFIRE: Exploring the Impact of Ionization, Excitation, and Nitrogen-to-Oxygen Ratio (2016, methodology): “Photometry and Sample Selection The photometric data available in the KBSS fields have been described in detail elsewhere (e.g., by Steidel et al. 2004; Reddy et al. 2012; Steidel et al. 2014).”
• Optical Selection of Star-forming Galaxies at Redshifts 1 < z < 3 (2004, unknown): “See Steidel et al. (2004) for a more detailed discussion.”
• The VIMOS VLT deep survey - First epoch VVDS-deep survey: 11 564 spectra with 17.5 $\leq$ I$_\textit{\textbf{\small AB}}$ $\leq$ 24, and the redshift distribution over 0 $\leq$ z $\leq$ 5 (2004, unknown): “Other groups have also recently efficiently explored this “redshift desert” (Abraham et al. 2004; Steidel et al. 2004).”
• Protoclusters associated with z > 2 radio galaxies - I. Characteristics of high redshift protoclusters (2006, methodology): “LRIS has two arms: a blue channel which is optimised for observations in the blue part of the optical spectrum (LRIS-B, see McCarthy et al., 1998; Steidel et al., 2004, for more information) and a red channel for observing in the red (LRIS-R, Oke et al. 1995).”
• Submillimeter Galaxies at z ~ 2: Evidence for Major Mergers and Constraints on Lifetimes, IMF, and CO-H2 Conversion Factor (2008, background): “5BX/BMgalaxies (e.g., Adelberger et al. 2004; Steidel et al. 2004; Erb et al. 2006b).”
• Evidence for Extended, Obscured Starbursts in Submillimeter Galaxies (2004, background): “…the entire extent of the systems, the obscurations we derive are considerably higher than those seen in high-redshift, rest-frame UV– selected populations, which are typically LFIR=LUV 0:1 100 (e.g., the Lyman break galaxies: Adelberger & Steidel 2000; or the BX/BM galaxies: Steidel et al. 2004).”
• CONSTRAINTS ON THE ASSEMBLY AND DYNAMICS OF GALAXIES. I. DETAILED REST-FRAME OPTICAL MORPHOLOGIES ON KILOPARSEC SCALE OF z ∼ 2 STAR-FORMING GALAXIES (2010, methodology): “Published data include ground-based optical UnGR imaging for all sources, and near-IRJ Ks imaging for a subset, presented by Erb et al. (2006, see also Steidel et al. 2004).”
• Calibrating Redshift Distributions beyond Spectroscopic Limits with Cross-Correlations (2008, background): “…tens of thousands of galaxies to R ∼ 24 or I ∼ 23 (Davis et al. 2006, in prep; Le Fèvre et al. 2005) and for a few thousand selected galaxies to R ∼ 25.5 (Steidel et al. 1999, 2003, 2004), but precise measurements of the redshift distributions of samples of galaxies with R ∼ 26− 27 or even…”
• The Mass-Metallicity Relation at z≳2 (2006, methodology): “The galaxies were selected by their rest-frame UV colors, and their redshifts were confirmed with rest-frame UV spectra from the LRIS-B spectrograph on the 10-m Keck I telescope; an overview of the z ∼ 2 sample is given by Steidel et al. (2004).”
• Cool Gas in High-Redshift Galaxies (2013, methodology): “A second color–selected sample is the rest–frame UV color selection technique, the BM/BX selection (Steidel et al. 2004).”
• The Rest-Frame Optical Properties of SCUBA Galaxies (2004, background): “Recent work by Steidel et al. (2004) has extended their photometric selection techniques to lower redshifts, z ¼ 1:4 2:6, giving a better match for comparison with the bulk of the SMG/OFRG population.”
• RECONCILING THE STELLAR AND NEBULAR SPECTRA OF HIGH-REDSHIFT GALAXIES (2016, methodology): “…wind feature has been discussed by many authors as a potential diagnostic because of its strength and its dependence on stellar metallicity (e.g., Pettini et al. 2000; Leitherer et al. 2001; Shapley et al. 2003; Rix et al. 2004; Steidel et al. 2004; Quider et al. 2009, 2010; Leitherer et al. 2010).”
• Erratum: From dwarf spheroidals to cD galaxies: simulating the galaxy population in a ΛCDM cosmology (2010, background): “This is motivated by observational data on high-redshift galaxies (e.g. Steidel et al. 2004; Quadri et al. 2008).”
• A Spectroscopic Survey of Redshift 1.4 ≲ z ≲ 3.0 Galaxies in the GOODS-North Field: Survey Description, Catalogs, and Properties (2006, methodology): “The optical imaging reduction and photometrywere done following the procedures described in Steidel et al. (2003, 2004).”
• A Redshift Survey of the Submillimeter Galaxy Population (2004, methodology): “The high fraction of UV-emission line galaxies in our sample (38/56 of those at high enough redshift to detect Lyα, or 68”
• THE GASEOUS ENVIRONMENT OF HIGH-z GALAXIES: PRECISION MEASUREMENTS OF NEUTRAL HYDROGEN IN THE CIRCUMGALACTIC MEDIUM OF z ∼ 2–3 GALAXIES IN THE KECK BARYONIC STRUCTURE SURVEY (2012, methodology): “In total, the KBSS galaxy sample includesR≃ 1000 (∼5-10Å) rest-UV spectra of 2188 star-forming galaxies obtained at the W.M. Keck Observatory using the Keck 1 10m telescope and the blue arm of the Low Resolution Imaging Spectrometer (LRIS-B; Oke et al. 1995; Steidel et al. 2004.)”