DUST OBSCURATION AND METALLICITY AT HIGH REDSHIFT: NEW INFERENCES FROM UV, Hα, AND 8 μm OBSERVATIONS OF z ∼ 2 STAR-FORMING GALAXIES

By Naveen A. Reddy, D. Erb, M. Pettini, C. Steidel, A. Shapley. 2010

279 citations recorded by the source corpus.

We use a sample of 90 spectroscopically confirmed Lyman break galaxies with Hα measurements and Spitzer MIPS 24 μm observations to constrain the relationship between rest-frame 8 μm luminosity (L8) and star formation rate (SFR) for L* galaxies at z ∼ 2. We find a tight correlation with 0.24 dex scatter between L8 and Hα luminosity/SFR for z ∼ 2 galaxies with 1010 L☉ ≲ LIR ≲ 1012 L☉. Employing this relationship with a larger sample of 392 galaxies with spectroscopic redshifts, we find that the UV slope β can be used to recover the dust attenuation of the vast majority of moderately luminous L* galaxies at z ∼ 2 to within a 0.4 dex scatter using the local correlation. Separately, young galaxies with ages ≲100 Myr appear to be less dusty than their UV slopes would imply based on the local trend and may follow an extinction curve that is steeper than what is typically assumed. Consequently, very young galaxies at high redshift may be significantly less dusty than inferred previously. Our results provide the first direct evidence, independent of the UV slope, for a correlation between UV and bolometric luminosity (Lbol) at high redshift, in the sense that UV-faint galaxies are on average less infrared and less bolometrically luminous than their UV-bright counterparts. The Lbol–LUV relation indicates that as the SFR increases, LUV turns over (or “saturates”) around the value of L* at z ∼ 2, implying that dust obscuration may be largely responsible for modulating the bright end of the UV luminosity function. Finally, dust attenuation is found to correlate with oxygen abundance at z ∼ 2. Accounting for systematic differences in local and high-redshift metallicity calibrations, we find that L* galaxies at z ∼ 2, while at least an order of magnitude more bolometrically luminous, exhibit ratios of metals to dust that are similar to those of local starbursts. This result is expected if high-redshift galaxies are forming their stars in a less metal-rich environment compared to local galaxies of the same luminosity, thus naturally leading to a redshift evolution in both the bolometric luminosity–metallicity and bolometric luminosity–obscuration relations.

Subfields: Astronomy and Astrophysics

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Citations in the corpus

• THE STAR FORMATION MASS SEQUENCE OUT TO z = 2.5 (2012, background): “The Effects of Dust Attenuation Previous studies have noted that dust attenuation is a strong function of stellar mass (e.g., Reddy et al. 2006, 2010; Pannella et al. 2009; Wuyts et al. 2011b), where the most massive galaxies are more highly obscured.”
• A POPULATION OF MASSIVE, LUMINOUS GALAXIES HOSTING HEAVILY DUST-OBSCURED GAMMA-RAY BURSTS: IMPLICATIONS FOR THE USE OF GRBs AS TRACERS OF COSMIC STAR FORMATION (2013, background): “…the standard one employed in most current high-z galaxy work (where it has generally been successful at modeling the UV SEDs of distant galaxies in current surveys; e.g., Calzetti & Heckman 1999; Reddy et al. 2010), and this convention facilitates direct comparison of the AV and SFR to other work.”
• PHIBSS: MOLECULAR GAS CONTENT AND SCALING RELATIONS IN z ∼ 1–3 MASSIVE, MAIN-SEQUENCE STAR-FORMING GALAXIES (2012, background): “Several authors (e.g. Förster Schreiber et al. 2009, Mancini et al. 2011, Wuyts et al. 2011b) find that this additional correction (typically resulting in a factor of ~2 upward correction of star formation rates) is preferable at z~2 (but see Erb et al. 2006, Reddy et al. 2010, 2012).”
• ON STAR FORMATION RATES AND STAR FORMATION HISTORIES OF GALAXIES OUT TO z ∼ 3 (2011, background): “In contrast, Reddy et al. (2010) found that such an extra attenuation correction towards HII regions may not be necessary.”
• GALAXY STRUCTURE AND MODE OF STAR FORMATION IN THE SFR–MASS PLANE FROM z ∼ 2.5 TO z ∼ 0.1 (2011, background): “…between bolometric luminosity and obscuration was presented previously for galaxies in the nearby universe (Heckman et al. 1998) and at z ∼ 2 (Reddy et al. 2010), but these authors did not trace the trend with SFR while specifically controlling for stellar mass. Likewise, an increase in…”
• THE MOSDEF SURVEY: MEASUREMENTS OF BALMER DECREMENTS AND THE DUST ATTENUATION CURVE AT REDSHIFTS z ∼ 1.4–2.6 (2015, methodology): “…inferences based on SED modeling of broad- and mediumband data and/or SFR comparisons (Reddy et al. 2006; Erb et al. 2006a; Noll et al. 2009; Reddy et al. 2010; Buat et al. 2011, 2012; Kriek & Conroy 2013), or have been investigated for galaxies over a limited range of spectral shape (e.g.,…”
• The HDUV Survey: A Revised Assessment of the Relationship between UV Slope and Dust Attenuation for High-redshift Galaxies (2017, methodology): “The general faintness of galaxies in our sample is underscored by their very low detection rate (S/N > 3) at 24µm—85 of 3,545 galaxies, or ≈ 2.4%—compared to the ≈ 40% detection rate for rest-frame UV-selected galaxies with R ≤ 25.5 (Reddy et al. 2010).”
• AN INTENSELY STAR-FORMING GALAXY AT z ∼ 7 WITH LOW DUST AND METAL CONTENT REVEALED BY DEEP ALMA AND HST OBSERVATIONS (2013, background): “Since the Small Magellanic Cloud (SMC) extinction has a smaller log(LFIR/L1600) value at a given β (see Figure 10 of Reddy et al. 2010) due to SMC’s steeper extinction curve in Aλ/AV-1/λ than that for local starbursts, it may be more appropriate for Himiko.”
• UV-CONTINUUM SLOPES AT z  ∼  4–7 FROM THE HUDF09+ERS+CANDELS OBSERVATIONS: DISCOVERY OF A WELL-DEFINED UV COLOR–MAGNITUDE RELATIONSHIP FOR z ⩾ 4 STAR-FORMING GALAXIES (2011, methodology): “…the colors might have been expected based on the evolution seen in the dust extinction vs. bolometric luminosity relationship from z ∼ 2 to z ∼ 0 (e.g., Reddy et al. 2006b, 2010; Buat et al. 2007) and also the evolution seen in the mass-metallicity relationship from z ∼ 3.5 to z ∼ 0 (e.g.,…”
• CONSTRAINTS ON THE ASSEMBLY AND DYNAMICS OF GALAXIES. II. PROPERTIES OF KILOPARSEC-SCALE CLUMPS IN REST-FRAME OPTICAL EMISSION OF z ∼ 2 STAR-FORMING GALAXIES (2011, background): “Spitzer/MIPS 24µm measurements that have been obtained for four of the targets (BX 389, BX 610, BX 528, and BX 663) indicate that they are among the 3% most luminous at rest-frame 8µm wavelengths of UV-selectedz∼ 2 galaxies (Reddy et al. 2010).”
• DIFFUSE Lyα EMITTING HALOS: A GENERIC PROPERTY OF HIGH-REDSHIFT STAR-FORMING GALAXIES (2011, methodology): “In the context of the assumed starburst attenuation relation, the extinction (in magnitudes) at 1500Å is A(1500Å) = 11.16E(B− V ) (Meurer et al. 1999; Calzetti et al. 2000; Reddy et al. 2006, 2010).”
• The rising star formation histories of distant galaxies and implications for gas accretion with time (2010, background): “…in their dust properties, and galaxies at fixed UV luminosity include both intrinsically less luminous galaxies with less dust extinction and intrinsically more luminous galaxies whose UV emission is obscured by dust (Reddy et al. 2010), and so we may expect the departure from the derived SFH.”
• VALIDATION OF THE EQUILIBRIUM MODEL FOR GALAXY EVOLUTION TO z ∼ 3 THROUGH MOLECULAR GAS AND DUST OBSERVATIONS OF LENSED STAR-FORMING GALAXIES (2013, background): “At high redshifts and at high total SFR (SFRtot), SFRIR is the dominant contribution (e.g. Pannella et al. 2009; Reddy et al. 2010; Wuyts et al. 2011b; Whitaker et al. 2012; Nordon et al. 2013; Heinis et al. 2013) and it is commonly assumed that SFRtot ∼ SFRIR, neglecting the un-obscured component…”
• THE FMOS-COSMOS SURVEY OF STAR-FORMING GALAXIES AT z ∼ 1.6. I. Hα-BASED STAR FORMATION RATES AND DUST EXTINCTION (2013, unknown): “While some studies at high-z support the validity of this relation (Förster Schreiber et al.2009; Wuyts et al. 2011; Mancini et al. 2011), Reddy et al. (2010) argue that such excess reddening for nebular emission may not be needed for UV-selected galaxies atz ∼ 2 (see also Onodera et al. 2010, for…”
• KECK SPECTROSCOPY OF 3 < z < 7 FAINT LYMAN BREAK GALAXIES: THE IMPORTANCE OF NEBULAR EMISSION IN UNDERSTANDING THE SPECIFIC STAR FORMATION RATE AND STELLAR MASS DENSITY (2012, background): “The latter appears to be appropriate for young galaxies (<100 Myr) at high redshift (Siana et al. 2008, Reddy et al. 2010, 2012), a population which might become increasingly dominant at z > 4.”
• STRONG NEBULAR LINE RATIOS IN THE SPECTRA of z ∼ 2–3 STAR FORMING GALAXIES: FIRST RESULTS FROM KBSS-MOSFIRE (2014, methodology): “…were applied to the Hα fluxes using the value of E(B − V)cont from the SED fits, which assumed the Calzetti et al. (2000) starburst attenuation relation (see e.g. Erb et al. 2006b; Reddy et al. 2010); the present KBSSMOSFIRE sample has 0≤ E(B − V)cont ≤ 0.8 with a median E(B − V)cont ' 0.2.”
• A study of the gas–star formation relation over cosmic time (2010, background): “…the applicability of the empirical Calzetti et al. (2000) extinction curve, although the inclusion of the extra factor of 2.3 for the ratio of nebular to continuum extinction may be questioned for high-z SFGs (see discussion in Foerster Schreiber et al. 2009; Reddy et al. 2010; Nordon et al. 2010).”