Metallicities and Physical Conditions in Star-forming Galaxies at z ~ 1.0-1.5

By Xin Liu, A. Shapley, A. Coil, J. Brinchmann, Chung-Pei Ma. 2008

160 citations recorded by the source corpus.

We present a study of the mass-metallicity (M-Z) relation and H II region physical conditions in a sample of 20 star-forming galaxies at 1.0 < z < 1.5 drawn from the DEEP2 Galaxy Redshift Survey. We find a correlation between stellar mass and gas-phase oxygen abundance in the sample and compare it with the one observed among UV-selected z ∼ 2 star-forming galaxies and local objects from the Sloan Digital Sky Survey (SDSS). This comparison, based on the same empirical abundance indicator, demonstrates that the zero point of the M-Z relationship evolves with redshift, in the sense that galaxies at fixed stellar mass become more metal-rich at lower redshift. Measurements of [O III]/Hβ and [N II]/Hα emission-line ratios show that, on average, objects in the DEEP2 1.0 < z < 1.5 sample are significantly offset from the excitation sequence observed in nearby H II regions and SDSS emission-line galaxies. In order to fully understand the causes of this offset, which is also observed in z ∼ 2 star-forming galaxies, we examine in detail the small fraction of SDSS galaxies that have similar diagnostic ratios to those of the DEEP2 sample. Some of these galaxies indicate evidence for AGN and/or shock activity, which may give rise to their unusual line ratios and contribute to Balmer emission lines at the level of ~20%. Others indicate no evidence for AGN or shock excitation yet are characterized by higher electron densities and temperatures, and therefore interstellar gas pressures, than typical SDSS star-forming galaxies of similar stellar mass. These anomalous objects also have higher concentrations and starformation rate surface densities, which are directly connected to higher interstellar pressure. Higher star formation rate surface densities, interstellar pressures, and H II region ionization parameters may also be common at high redshift. These effects must be taken into account when using strong-line indicators to understand the evolution of heavy elements in galaxies. When such effects are included, the inferred evolution of the M-Z relation out to z ∼ 2 is more significant than previous estimates.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/0c77983096476858948f3ae87fb8276f00a2425c

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Citations in the corpus

• PHYSICAL CONDITIONS IN A YOUNG, UNREDDENED, LOW-METALLICITY GALAXY AT HIGH REDSHIFT (2010, background): “Next we observe that the few z ∼ 2 galaxies for which all four emission lines have been detected lie significantly to the right of the probable location of BX418 (and from the sequence of local star-forming galaxies; see Liu et al. 2008 and Brinchmann et al. 2008b).”
• The evolution of the dust temperatures of galaxies in the SFR–M∗ plane up to z ~ 2 (2013, background): “In the stellar mass range of our study (i.e., 1010 M < M∗ < 1011.5), the metallicity μ of galaxies systematically decreases by ∼0.5 dex from z = 0 to z = 2 (z = 0, Tremonti et al. 2004; z = 2, Erb et al. 2006; Shapley et al. 2005; Liu et al. 2008; Zahid et al. 2013; see also Genzel et al. 2012).”
• THE HOST GALAXIES OF GAMMA-RAY BURSTS. II. A MASS–METALLICITY RELATION FOR LONG-DURATION GAMMA-RAY BURST HOST GALAXIES (2010, background): “The metallicity of the star-forming galaxy population is known to evolve with redshift; galaxies at z ≥ 1 are less enriched and have lower metallicities on average (e.g., Kobulnicky & Kewley 2004, Shapley et al. 2004, Erb et al. 2006, Chary et al. 2007, Davè & Oppenheimer 2007, Liu et al. 2008).”
• THE MOSDEF SURVEY: EXCITATION PROPERTIES OF z ∼ 2.3 STAR-FORMING GALAXIES (2014, methodology): “Both Liu et al. (2008) and Newman et al. (2014) conclude that the N2 indicator will overestimate gas-phase oxygen abundances for high-redshift galaxies, while Liu et al. (2008) and Steidel et al. (2014) conclude that the O3N2 indicator should not be significantly biased, relative to its use in the…”
• STRONG NEBULAR LINE RATIOS IN THE SPECTRA of z ∼ 2–3 STAR FORMING GALAXIES: FIRST RESULTS FROM KBSS-MOSFIRE (2014, methodology): “…had already been suggested by the relatively small number of earlier measurements for galaxies at z ∼ 1 − 2.5 (Shapley et al. 2005a; Erb et al. 2006a; Liu et al. 2008): the nebular spectra of high redshift star-forming galaxies occupy an almost entirely distinct region of the BPT diagram as…”
• THE MOSFIRE DEEP EVOLUTION FIELD (MOSDEF) SURVEY: REST-FRAME OPTICAL SPECTROSCOPY FOR ∼1500 H-SELECTED GALAXIES AT 1.37 ≤ z ≤ 3.8 ?> (2014, background): “The origin of these differences may reflect fundamental differences in distant H ii regions (e.g., Liu et al. 2008; Brinchmann et al. 2008) and may have severe implications for metallicity measurements of galaxies.”
• LSD: Lyman-break galaxies Stellar populations and Dynamics – I. Mass, metallicity and gas at z∼ 3.1 (2009, background): “…stellar mass or larger circular velocity have higher metallicities (Garnett 2002; Pérez-González et al. 2003; Pilyugin, Vı́lchez & Contini 2004; Tremonti et al. 2004; Lee et al. 2006; Hayashi et al. 2008; Kewley & Ellison 2008; Liu et al. 2008; Michel-Dansac et al. 2008; Panter et al. 2008).”
• DWARF GALAXIES WITH OPTICAL SIGNATURES OF ACTIVE MASSIVE BLACK HOLES (2013, background): “Composite objects are thought to contain significant contributions from both AGN and star formation (e.g., Panessa et al. 2005; Kewley et al. 2006; Trouille et al. 2011, but also see Liu et al. (2008)).”
• A NEW DIAGNOSTIC OF ACTIVE GALACTIC NUCLEI: REVEALING HIGHLY ABSORBED SYSTEMS AT REDSHIFT >0.3 (2011, background): “Some attributed this trend to varying HII region conditions (Liu et al. 2008; Brinchmann et al. 2008; Hainline et al. 2009) while others claim that additional AGN contribution may be the driving factor (Groves et al. 2006; Wright et al. 2010).”
• REST-FRAME OPTICAL SPECTRA OF THREE STRONGLY LENSED GALAXIES AT z ∼ 2 (2009, methodology): “Another idea discussed in Brinchmann et al. (2008) and Liu et al. (2008) is that the higher ionization parameter that might lead to this offset on the BPT diagram is due to a higher density in the H II regions.”
• EXTRAGALACTIC CHEMICAL ABUNDANCES: DO H ii REGIONS AND YOUNG STARS TELL THE SAME STORY? THE CASE OF THE SPIRAL GALAXY NGC 300 (2009, background): “…Shapley et al. 2004), allowing the investigation of cosmic chemical enrichment (Kobulnicky & Kewley 2004; Savaglio et al. 2005; Maier et al. 2006; Liu et al. 2008; Cowie & Barger 2008) in connection to fundamental properties of galaxies such as the mass-metallicity relation (Lequeux et al. 1979;…”
• EVIDENCE FOR WIDE-SPREAD ACTIVE GALACTIC NUCLEUS-DRIVEN OUTFLOWS IN THE MOST MASSIVE z ∼ 1–2 STAR-FORMING GALAXIES (2014, background): “The SINFONI data alone have too low S/N for our analysis, so we used the combined GNIRS+SINFONI spectra as published by Kriek et al. with the following exception.”
• THE MOSDEF SURVEY: ELECTRON DENSITY AND IONIZATION PARAMETER AT z ∼ 2.3 (2015, background): “…produced showing that galaxies at z ∼ 1− 2 display certain emission line ratios that are atypical of local star-forming galaxies (e.g., Shapley et al. 2005; Erb et al. 2006; Liu et al. 2008; Hainline et al. 2009; Holden et al. 2014; Nakajima & Ouchi 2014; Steidel et al. 2014; Shapley et al. 2015).”
• Ionization state of inter-stellar medium in galaxies: evolution, SFR-M * -Z dependence, and ionizing photon escape (2013, background): “In contrast, high-z galaxies depart from the local star-forming sequence towards higher [O III]/Hβ ratio (e.g. Shapley et al. 2005; Erb et al. 2006; Liu et al. 2008; Hainline et al. 2009; Finkelstein et al. 2009; Yabe et al. 2012).”
• PHYSICAL PROPERTIES OF EMISSION-LINE GALAXIES AT z ∼ 2 FROM NEAR-INFRARED SPECTROSCOPY WITH MAGELLAN FIRE (2014, background): “This trend has been 13 noted in previous studies (Shapley et al. 2005; Erb et al. 2006; Liu et al. 2008; Hainline et al. 2009; Newman et al. 2013), and has been linked to higher ionization parameters, on average, in star-forming galaxies at high redshift (e.g. Brinchmann et al. 2008b; Kewley et al.…”
• Chemical abundances in high-redshift galaxies: a powerful new emission line diagnostic (2016, background): “It is likely that a change in both ionization parameter and in the ISM pressure is responsible for this difference (Brinchmann et al. 2008; Liu et al. 2008; Hainline et al. 2009; Bian et al. 2010; Nakajima et al. 2012; Kewley et al. 2013a).”
• OPTICAL SPECTROSCOPY AND NEBULAR OXYGEN ABUNDANCES OF THE SPITZER/SINGS GALAXIES (2010, background): “…galaxies in the nearby universe, and may not be applicable at higher redshift where the physical conditions in galaxies may differ dramatically from physical conditions in local galaxies (Shapley et al. 2005; Liu et al. 2008; Brinchmann et al. 2008; Hainline et al. 2009; Lehnert et al. 2009).”