STRONG NEBULAR LINE RATIOS IN THE SPECTRA of z ∼ 2–3 STAR FORMING GALAXIES: FIRST RESULTS FROM KBSS-MOSFIRE

We present initial results of a deep near-IR spectroscopic survey covering the 15 fields of the Keck Baryonic Structure Survey using the recently commissioned MOSFIRE spectrometer on the Keck 1 telescope. We focus on a sample of 251 galaxies with redshifts 2.0 < z < 2.6, star formation rates (SFRs) 2 ≾ SFR ≾ 200 M_☉ yr^(–1), and stellar masses 8.6 < log (M_*/M_☉) < 11.4, with high-quality spectra in both H- and K-band atmospheric windows. We show unambiguously that the locus of z ~ 2.3 galaxies in the "BPT" nebular diagnostic diagram exhibits an almost entirely disjointed, yet similarly tight, relationship between the line ratios [N II] λ6585/Hα and [O III]/Hβ as compared to local galaxies. Using photoionization models, we argue that the offset of the z ~ 2.3 BPT locus relative to that at z ~ 0 is caused by a combination of harder stellar ionizing radiation field, higher ionization parameter, and higher N/O at a given O/H compared to most local galaxies, and that the position of a galaxy along the z ~ 2.3 star-forming BPT locus is surprisingly insensitive to gas-phase oxygen abundance. The observed nebular emission line ratios are most easily reproduced by models in which the net stellar ionizing radiation field resembles a blackbody with effective temperature T_(eff) = 50, 000-60, 000 K, the gas-phase oxygen abundances lie in the range 0.2 < Z/Z_☉ < 1.0, and the ratio of gas-phase N/O is close to the solar value. We critically assess the applicability at high redshift of commonly used strong line indices for estimating gas-phase metallicity, and consider the implications of the small intrinsic scatter of the empirical relationship between excitation-sensitive line indices and M_* (i.e., the "mass-metallicity" relation) at z ≃ 2.3.

[1]  S. McGaugh,et al.  H II region abundances - Model oxygen line ratios , 1991 .

[2]  S. Charlot,et al.  Nebular emission from star-forming galaxies , 2001, astro-ph/0101097.

[3]  L. Kewley,et al.  THE COSMIC BPT DIAGRAM: CONFRONTING THEORY WITH OBSERVATIONS , 2013, 1307.0514.

[4]  L. Kewley,et al.  NEW STRONG-LINE ABUNDANCE DIAGNOSTICS FOR H ii REGIONS: EFFECTS OF κ-DISTRIBUTED ELECTRON ENERGIES AND NEW ATOMIC DATA , 2013, 1307.5950.

[5]  E. Gawiser,et al.  Accepted for publication in ApJ Preprint typeset using L ATEX style emulateapj v. 10/09/06 A NEAR-INFRARED SPECTROSCOPIC SURVEY OF K-SELECTED GALAXIES AT z ∼ 2.3: REDSHIFTS AND IMPLICATIONS FOR BROADBAND PHOTOMETRIC STUDIES 1,2 , 2022 .

[6]  C. Steidel,et al.  THE HALO MASSES AND GALAXY ENVIRONMENTS OF HYPERLUMINOUS QSOs AT z ≃ 2.7 IN THE KECK BARYONIC STRUCTURE SURVEY , 2012, 1204.3636.

[7]  C. Steidel,et al.  Evidence for Solar Metallicities in Massive Star-forming Galaxies at z ≳ 2 , 2004, astro-ph/0405187.

[8]  G. Stasińska.  Biases in abundance derivations for metal-rich nebulae , 2005, astro-ph/0501574.

[9]  C. Steidel,et al.  NEUTRAL HYDROGEN OPTICAL DEPTH NEAR STAR-FORMING GALAXIES AT z ≈ 2.4 IN THE KECK BARYONIC STRUCTURE SURVEY , 2011, 1109.4944.

[10]  C. Steidel,et al.  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, 1202.6055.

[11]  L. Kewley,et al.  Theoretical Modeling of Starburst Galaxies , 2001, astro-ph/0106324.

[12]  D. Elbaz,et al.  VERY HIGH GAS FRACTIONS AND EXTENDED GAS RESERVOIRS IN z = 1.5 DISK GALAXIES , 2009, 0911.2776.

[13]  J. Hjorth,et al.  Gravitationally lensed galaxies at 2 < z < 3.5: direct abundance measurements of Ly α emitters , 2012, 1209.0775.

[14]  Donald E. Osterbrock,et al.  Spectral Classification of Emission-Line Galaxies , 1987 .

[15]  J. Dunlop,et al.  The Mass-Metallicity-SFR Relation at z >~ 2 with 3D-HST , 2013, 1310.0816.

[16]  Accepted for publication in ApJ Preprint typeset using L ATEX style emulateapj v. 11/26/03 THE KINEMATICS OF MORPHOLOGICALLY SELECTED Z ∼ 2 GALAXIES IN THE GOODS-NORTH FIELD 1 , 2004 .

[17]  C. Steidel,et al.  THE CHARACTERISTIC STAR FORMATION HISTORIES OF GALAXIES AT REDSHIFTS z ∼ 2–7 , 2012, 1205.0555.

[18]  Shy Genel,et al.  THE SINS SURVEY: SINFONI INTEGRAL FIELD SPECTROSCOPY OF z ∼ 2 STAR-FORMING GALAXIES , 2009, 0903.1872.

[19]  D. Tucker,et al.  REST-FRAME OPTICAL SPECTRA OF THREE STRONGLY LENSED GALAXIES AT z ∼ 2 , 2009, 0906.2197.

[20]  C. Steidel,et al.  The Stellar, Gas, and Dynamical Masses of Star-forming Galaxies at z ~ 2 , 2006, astro-ph/0604041.

[21]  G. Chabrier.  Galactic Stellar and Substellar Initial Mass Function , 2003, astro-ph/0304382.

[22]  C. Steidel,et al.  C, N, O abundances in the most metal-poor damped Lyman alpha systems★ , 2007, 0712.1829.

[23]  Max Pettini,et al.  Optical Selection of Star-forming Galaxies at Redshifts 1 < z < 3 , 2004, astro-ph/0401445.

[24]  M. C. Cooper,et al.  High molecular gas fractions in normal massive star-forming galaxies in the young Universe , 2010, Nature.

[25]  Leiden,et al.  New insights into the stellar content and physical conditions of star-forming galaxies at z = 2-3 from spectral modelling , 2008, 0801.1678.

[26]  G. Worthey,et al.  Publications of the Astronomical Society of the Pacific The Distribution Of Heavy Elements In Spiral And Elliptical Galaxies , 1999 .

[27]  E. Stanway,et al.  The effect of stellar evolution uncertainties on the rest-frame ultraviolet stellar lines of C iv and He ii in high-redshift Lyman-break galaxies , 2011, 1109.0288.

[28]  Geoffrey C. Clayton,et al.  A Quantitative Comparison of SMC, LMC, and Milky Way UV to NIR Extinction Curves , 2003, astro-ph/0305257.

[29]  J. Brinchmann,et al.  Metallicities and Physical Conditions in Star-forming Galaxies at z ~ 1.0-1.5 , 2008, 0801.1670.

[30]  D. Burgarella,et al.  DETECTIONS OF LYMAN CONTINUUM FROM STAR-FORMING GALAXIES AT z ∼ 3 THROUGH SUBARU/SUPRIME-CAM NARROW-BAND IMAGING , 2008, 0805.4012.

[31]  Larkin,et al.  The Rest-Frame Optical Spectrum of MS 1512-cB58. , 2000, The Astrophysical journal.

[32]  Max Pettini Alice E. Shapley Charles C. Steidel Jean-G Giavalisco.  The Rest-Frame Optical Spectra of Lyman Break Galaxies: Star Formation, Extinction, Abundances, and Kinematics* , 2001 .

[34]  M. Wolff,et al.  A Quantitative Comparison of the Small Magellanic Cloud, Large Magellanic Cloud, and Milky Way Ultraviolet to Near-Infrared Extinction Curves , 2003 .

[35]  James E. Larkin,et al.  THE KILOPARSEC-SCALE KINEMATICS OF HIGH-REDSHIFT STAR-FORMING GALAXIES , 2009, 0901.2930.

[36]  Abundances in Spiral Galaxies: Evidence for Primary Nitrogen Production , 1998, astro-ph/9802147.

[37]  Henry A. Kobulnicky,et al.  Electronic Mail: , 1998 .

[38]  E. Stanway,et al.  Spectral population synthesis including massive binaries , 2009, 0908.1386.

[39]  Marcia J. Rieke,et al.  TURNING BACK THE CLOCK: INFERRING THE HISTORY OF THE EIGHT O'CLOCK ARC , 2009, 0905.1122.

[40]  D.Lutz,et al.  PHIBSS: MOLECULAR GAS CONTENT AND SCALING RELATIONS IN z ∼ 1-3 MASSIVE, MAIN-SEQUENCE STAR-FORMING GALAXIES* , 2012 .

[41]  R. Kudritzki,et al.  WINDS FROM HOT STARS , 2000 .

[42]  A. Tielens,et al.  LINE EMISSION FROM RADIATION-PRESSURIZED H ii REGIONS. I. INTERNAL STRUCTURE AND LINE RATIOS , 2013, 1303.4742.

[43]  James E. Larkin,et al.  THE PRESENCE OF WEAK ACTIVE GALACTIC NUCLEI IN HIGH REDSHIFT STAR-FORMING GALAXIES , 2010, 1001.5041.

[44]  Sean Adkins,et al.  MOSFIRE, the multi-object spectrometer for infra-red exploration at the Keck Observatory , 2012, Other Conferences.

[45]  E. Jullo,et al.  THE ORIGIN AND EVOLUTION OF METALLICITY GRADIENTS: PROBING THE MODE OF MASS ASSEMBLY AT z ≃ 2 , 2012, 1207.4489.

[46]  J. Baldwin,et al.  ERRATUM - CLASSIFICATION PARAMETERS FOR THE EMISSION-LINE SPECTRA OF EXTRAGALACTIC OBJECTS , 1981 .

[47]  C. Steidel,et al.  DUST OBSCURATION AND METALLICITY AT HIGH REDSHIFT: NEW INFERENCES FROM UV, Hα, AND 8 μm OBSERVATIONS OF z ∼ 2 STAR-FORMING GALAXIES , 2010, 1002.0837.

[48]  G. Zamorani,et al.  NEBULAR EXCITATION IN z ∼ 2 STAR-FORMING GALAXIES FROM THE SINS AND LUCI SURVEYS: THE INFLUENCE OF SHOCKS AND ACTIVE GALACTIC NUCLEI , 2013, 1306.6676.

[49]  A. Tielens,et al.  LINE EMISSION FROM RADIATION-PRESSURIZED H ii REGIONS. II. DYNAMICS AND POPULATION SYNTHESIS , 2013, 1303.4737.

[50]  B. Kelly.  Some Aspects of Measurement Error in Linear Regression of Astronomical Data , 2007, 0705.2774.

[51]  C. Steidel,et al.  STELLAR POPULATIONS OF ULTRAVIOLET-SELECTED ACTIVE GALACTIC NUCLEI HOST GALAXIES AT z ∼ 2–3 , 2012, 1206.3308.

[52]  L. Kewley,et al.  Metallicity Calibrations and the Mass-Metallicity Relation for Star-forming Galaxies , 2008, 0801.1849.

[53]  L. Pozzetti,et al.  The Star Formation History of Field Galaxies , 1997, astro-ph/9708220.

[54]  Alison L. Coil,et al.  THE MOSDEF SURVEY: MASS, METALLICITY, AND STAR-FORMATION RATE AT z ∼ 2.3 , 2014, 1408.2521.

[55]  P. McCarthy,et al.  LOW MASSES AND HIGH REDSHIFTS: THE EVOLUTION OF THE MASS–METALLICITY RELATION , 2013, 1309.4458.

[56]  S. J. Lilly,et al.  Evidence for Wide-spread Active Galactic Nucleus-driven Outflows in the Most Massive z ~ 1-2 Star-forming Galaxies , 2014 .

[57]  M. Oey,et al.  THE ORIGIN AND OPTICAL DEPTH OF IONIZING RADIATION IN THE “GREEN PEA” GALAXIES , 2013, 1301.0530.

[58]  R. Bender,et al.  A CONSISTENT STUDY OF METALLICITY EVOLUTION AT 0.8 < z < 2.6 , 2014, 1405.6590.

[59]  J. Rigby,et al.  THE PHYSICAL CONDITIONS OF A LENSED STAR-FORMING GALAXY AT z = 1.7 , 2011, 1102.2441.

[60]  J. Brinchmann,et al.  STARS WERE BORN IN SIGNIFICANTLY DENSER REGIONS IN THE EARLY UNIVERSE , 2013, 1307.4758.

[61]  STAR FORMATION IN GALAXIES ALONG THE HUBBLE SEQUENCE , 1998, astro-ph/9807187.

[62]  C. Leitherer,et al.  THE EFFECTS OF STELLAR ROTATION. I. IMPACT ON THE IONIZING SPECTRA AND INTEGRATED PROPERTIES OF STELLAR POPULATIONS , 2012, 1203.5109.

[63]  J. V'ilchez,et al.  THE STAR FORMATION HISTORY AND METAL CONTENT OF THE GREEN PEAS. NEW DETAILED GTC-OSIRIS SPECTROPHOTOMETRY OF THREE GALAXIES , 2012, 1202.3419.

[64]  J. V'ilchez,et al.  ON THE OXYGEN AND NITROGEN CHEMICAL ABUNDANCES AND THE EVOLUTION OF THE “GREEN PEA” GALAXIES , 2010, 1004.4910.

[65]  L. Kewley,et al.  A Theoretical Recalibration of the Extragalactic H II Region Sequence , 2000 .

[66]  C. Steidel,et al.  THE REST-FRAME ULTRAVIOLET SPECTRA OF UV-SELECTED ACTIVE GALACTIC NUCLEI AT z ∼ 2–3 , 2010, 1012.0075.

[67]  M. Asplund,et al.  The chemical composition of the Sun , 2009, 0909.0948.

[68]  S. J. Lilly,et al.  The Sins/zC-Sinf survey of z ~ 2 galaxy kinematics: evidence for powerful active galactic nucleus-driven nuclear outflows in massive star-forming galaxies , 2013 .

[69]  Timothy M. Heckman,et al.  The host galaxies of active galactic nuclei , 2003 .

[70]  T. Contini,et al.  The impact of the nitrogen-to-oxygen ratio on ionized nebula diagnostics based on [N ii] emission lines , 2009, 0905.4621.

[71]  C. Steidel,et al.  X-Ray and Radio Emission from Ultraviolet-selected Star-forming Galaxies at Redshifts 1.5 ≲ z ≲ 3.0 in the GOODS-North Field , 2004, astro-ph/0401432.

[72]  M. Giavalisco,et al.  Infrared Observations of Nebular Emission Lines from Galaxies at z ≃ 3 , 1998, astro-ph/9806219.

[73]  C. Steidel,et al.  THE MASS–METALLICITY RELATION OF A z ∼ 2 PROTOCLUSTER WITH MOSFIRE , 2013, 1306.6334.

[74]  J. Mathis,et al.  The relationship between infrared, optical, and ultraviolet extinction , 1989 .

[75]  L. Kewley,et al.  FIRST DIRECT METALLICITY MEASUREMENT OF A LENSED STAR-FORMING GALAXY AT z = 1.7 , 2009, 0906.0371.

[76]  J. Trump,et al.  ACTIVE GALACTIC NUCLEI EMISSION LINE DIAGNOSTICS AND THE MASS–METALLICITY RELATION UP TO REDSHIFT z ∼ 2: THE IMPACT OF SELECTION EFFECTS AND EVOLUTION , 2014, 1403.6832.

[77]  L. Kewley,et al.  Accepted for publication in The Astrophysical Journal Preprint typeset using L ATEX style emulateapj v. 6/22/04 HIGH-RESOLUTION MEASUREMENTS OF THE HALOS OF FOUR DARK MATTER-DOMINATED GALAXIES: DEVIATIONS FROM A UNIVERSAL DENSITY PROFILE 1 , 2004 .

[78]  The Population of Faint Optically Selected Active Galactic Nuclei at z ~ 3 , 2002, astro-ph/0205142.

[79]  Harvard-Smithsonian CfA,et al.  Using Strong Lines to Estimate Abundances in Extragalactic H II Regions and Starburst Galaxies , 2002, astro-ph/0206495.

[80]  A. Coil,et al.  Chemical Abundances of DEEP2 Star-forming Galaxies at z~1.0-1.5 , 2005, astro-ph/0509102.

[81]  C. Steidel,et al.  The Rest-Frame Ultraviolet Spectra Of UV-Selected Active Galactic Nuclei At Z Similar To 2-3 , 2011 .

[82]  Johan Richard,et al.  Resolved spectroscopy of gravitationally lensed galaxies: recovering coherent velocity fields in subluminous z ~ 2-3 galaxies , 2009, 0910.4488.

[83]  A reappraisal of the chemical composition of the Orion nebula based on Very Large Telescope echelle spectrophotometry , 2004, astro-ph/0408249.

[84]  High velocity dispersion in a rare grand-design spiral galaxy at redshift z = 2.18 , 2012, Nature.

[85]  David R. Law,et al.  AN HST/WFC3-IR MORPHOLOGICAL SURVEY OF GALAXIES AT z = 1.5–3.6. I. SURVEY DESCRIPTION AND MORPHOLOGICAL PROPERTIES OF STAR-FORMING GALAXIES , 2011, 1107.3137.

[86]  D. Elbaz,et al.  GOODS-HERSCHEL MEASUREMENTS OF THE DUST ATTENUATION OF TYPICAL STAR-FORMING GALAXIES AT HIGH REDSHIFT: OBSERVATIONS OF ULTRAVIOLET-SELECTED GALAXIES AT z ∼ 2 , 2011, 1107.2653.

[87]  Nebular and stellar properties of a metal-poor H ii galaxy at z= 3.36 , 2004, astro-ph/0409352.

[88]  V. Wild,et al.  Evolution of the Stellar Mass-Metallicity Relation Since z=0.75 , 2011, 1112.3300.

[89]  C. C. Steidel,et al.  NARROWBAND IMAGING OF ESCAPING LYMAN-CONTINUUM EMISSION IN THE SSA22 FIELD, , 2011, 1102.0286.

[90]  Naveen A. Reddy,et al.  NARROWBAND LYMAN-CONTINUUM IMAGING OF GALAXIES AT z ∼ 2.85 , 2013, 1306.1535.

[91]  C. Steidel,et al.  Accepted for publication in ApJ Preprint typeset using L ATEX style emulateapj v. 12/14/05 Hα OBSERVATIONS OF A LARGE SAMPLE OF GALAXIES AT z ∼ 2: IMPLICATIONS FOR STAR FORMATION IN HIGH REDSHIFT GALAXIES 1 , 2006 .

[92]  A. Fontana,et al.  EVIDENCE OF VERY LOW METALLICITY AND HIGH IONIZATION STATE IN A STRONGLY LENSED, STAR-FORMING DWARF GALAXY AT z = 3.417 , 2014, 1403.6470.

[93]  B. Lundgren,et al.  DIRECT MEASUREMENTS OF DUST ATTENUATION IN z ∼ 1.5 STAR-FORMING GALAXIES FROM 3D-HST: IMPLICATIONS FOR DUST GEOMETRY AND STAR FORMATION RATES , 2013, 1310.4177.

[94]  C. Steidel,et al.  THE STRUCTURE AND KINEMATICS OF THE CIRCUMGALACTIC MEDIUM FROM FAR-ULTRAVIOLET SPECTRA OF z ≃ 2–3 GALAXIES , 2010, 1003.0679.

[95]  Max Pettini,et al.  [O III] / [N II] as an abundance indicator at high redshift , 2004, astro-ph/0401128.

[96]  B. Tinsley,et al.  Composition gradients across spiral galaxies. II - The stellar mass limit , 1976 .

[97]  G. Bruzual,et al.  Stellar population synthesis at the resolution of 2003 , 2003, astro-ph/0309134.

[98]  D. Kelson.  Optimal Techniques in Two‐dimensional Spectroscopy: Background Subtraction for the 21st Century , 2003, astro-ph/0303507.

[99]  M. Giavalisco,et al.  Lyman Break Galaxies at Redshift z ~ 3: Survey Description and Full Data Set , 2003, astro-ph/0305378.

[100]  C. Steidel,et al.  PHYSICAL CONDITIONS IN A YOUNG, UNREDDENED, LOW-METALLICITY GALAXY AT HIGH REDSHIFT , 2010, 1006.5456.

[101]  Max Pettini,et al.  The Mass-Metallicity Relation at z≳2 , 2006, astro-ph/0602473.

[102]  Harland Epps,et al.  Design and development of MOSFIRE: the multi-object spectrometer for infrared exploration at the Keck Observatory , 2010, Astronomical Telescopes + Instrumentation.

[103]  L. Kewley,et al.  THEORETICAL EVOLUTION OF OPTICAL STRONG LINES ACROSS COSMIC TIME , 2013, 1307.0508.

[104]  C. Lintott,et al.  Galaxy Zoo Green Peas: discovery of a class of compact extremely star-forming galaxies , 2009, 0907.4155.

[105]  C. Evans,et al.  Rotating massive main-sequence stars - I. Grids of evolutionary models and isochrones , 2011, 1102.0530.

[106]  L. Kewley,et al.  THE UNIVERSAL RELATION OF GALACTIC CHEMICAL EVOLUTION: THE ORIGIN OF THE MASS–METALLICITY RELATION , 2014, 1404.7526.

[107]  M. Edmunds,et al.  The nitrogen-to-oxygen ratio in galaxies and its implications for the origin of nitrogen , 1993 .

[108]  AMAZE - I. The evolution of the mass–metallicity relation at z $>$ 3 , 2008, 0806.2410.

[109]  E. Salpeter.  The Luminosity function and stellar evolution , 1955 .

[110]  J. Cuby,et al.  Hα Spectroscopy of Galaxies at z > 2: Kinematics and Star Formation , 2003, astro-ph/0303392.

[111]  M. Oguri,et al.  THE PHYSICAL CONDITIONS, METALLICITY AND METAL ABUNDANCE RATIOS IN A HIGHLY MAGNIFIED GALAXY AT z = 3.6252 , 2013, 1310.6695.

[112]  F. Mannucci,et al.  Metallicity evolution, metallicity gradients, and gas fractions at z ~ 3.4 , 2013, 1311.4576.

[113]  J. Dunlop,et al.  The mass–metallicity–star formation rate relation at $\boldsymbol {z \gtrsim 2}$ with 3D Hubble Space Telescope , 2014 .

[114]  Bernard E. J. Pagel,et al.  On the composition of H II regions in southern galaxies – I. NGC 300 and 1365 , 1979 .

[115]  The Physical Properties and Effective Temperature Scale of O-Type Stars as a Function of Metallicity. II. Analysis of 20 More Magellanic Cloud Stars and Results from the Complete Sample , 2005, astro-ph/0503464.

[116]  C. I. O. Technology.,et al.  Metal-line absorption around z ≈ 2.4 star-forming galaxies in the Keck Baryonic Structure Survey , 2014, 1403.0942.

[117]  L. Christensen,et al.  Testing Metallicity Indicators at Z ~ 1.4 with the Gravitationally Lensed Galaxy CASSOWARY 20* , 2013, 1311.5092.

[118]  Physical properties of emission-line galaxies at z ∼ 2 from near-infrared spectroscopy with magellan fire , 2014, 1402.0510.

[119]  A. Kinney,et al.  The Dust Content and Opacity of Actively Star-forming Galaxies , 1999, astro-ph/9911459.

[120]  M. Swinbank,et al.  The emission line properties of gravitationally lensed 1.5 < z < 5 galaxies , 2010, 1011.6413.

[121]  J. Rigby,et al.  CONSTRAINTS ON THE LOW-MASS END OF THE MASS–METALLICITY RELATION AT z = 1–2 FROM LENSED GALAXIES , 2012, 1202.5267.

[122]  B. Andrews,et al.  THE MASS–METALLICITY RELATION WITH THE DIRECT METHOD ON STACKED SPECTRA OF SDSS GALAXIES , 2012, 1211.3418.

[123]  Andreas Burkert,et al.  THE SINS/zC-SINF SURVEY OF z ∼ 2GALAXY KINEMATICS: THE NATURE OF DISPERSION-DOMINATED GALAXIES , 2012, 1211.6160.

[124]  The Host Galaxies of AGN , 2003, astro-ph/0304239.

[125]  M. Pettini,et al.  A Survey of Star-forming Galaxies in the 1.4 ≲ z ≲ 2.5 Redshift Desert: Overview , 2004, astro-ph/0401439.