Search

We present ionized gas kinematics for 681 galaxies at z &tild; 1.4-3.8 from the MOSFIRE Deep Evolution Field survey, measured using models that account for random galaxy-slit misalignments together with structural parameters derived from CANDELS Hubble Space Telescope (HST) imaging. Kinematics and sizes are used to derive dynamical masses. Baryonic masses are estimated from stellar masses and inferred gas masses from dust-corrected star formation rates (SFRs) and the Kennicutt-Schmidt relation. We measure resolved rotation for 105 galaxies. For the remaining 576 galaxies we use models based on HST imaging structural parameters together with integrated velocity dispersions and baryonic masses to statistically constrain the median ratio of intrinsic ordered to disordered motion,. We find that increases with increasing stellar mass and decreasing specific SFR (sSFR). These trends may reflect marginal disk stability, where systems with higher gas fractions have thicker disks. For galaxies with detected rotation we assess trends between their kinematics and mass, sSFR, and baryon surface density (Σbar,e). Intrinsic dispersion correlates most with Σbar,e, and velocity correlates most with mass. By comparing dynamical and baryonic masses, we find that galaxies at z &tild; 1.4-3.8 are baryon dominated within their effective radii (RE), with Mdyn/Mbaryon increasing over time. The inferred baryon fractions within RE, fbar, decrease over time, even at fixed mass, size, or surface density. At fixed redshift, fbar does not appear to vary with stellar mass but increases with decreasing RE and increasing Σbar,e. For galaxies at z ≥ 2, the median inferred baryon fractions generally exceed 100%. We discuss possible explanations and future avenues to resolve this tension.

Using data from the MOSFIRE Deep Evolution Field (MOSDEF) survey, we present a census of active galactic nucleus (AGN)-driven ionized outflows in a sample of 159 AGNs at 1.4 ≤ z ≤ 3.8. The sample spans AGN bolometric luminosities of 1044-47 erg s-1 and includes both quiescent and star-forming galaxies extending across 3 orders of magnitude in stellar mass. We identify and characterize outflows from the Hβ, [O iii], H, and [N ii] emission line spectra. We detect outflows in 17% of the AGNs, seven times more often than in a mass-matched sample of inactive galaxies in MOSDEF. The outflows are fast and galaxy-wide, with velocities of ∼400-3500 km s-1 and spatial extents of 0.3-11.0 kpc. The incidence of outflows among AGNs is independent of the stellar mass of the host galaxy, with outflows detected in both star-forming and quiescent galaxies. This suggests that outflows exist across different phases in galaxy evolution. We investigate relations between outflow kinematic, spatial, and energetic properties and both AGN and host galaxy properties. Our results show that AGN-driven outflows are widespread in galaxies along the star-forming main sequence. The mass-loading factors of the outflows are typically 0.1-1 and increase with AGN luminosity, capable of exceeding unity at at LAGN≳ 1046 erg s-1. In these more luminous sources, the ionized outflow alone is likely sufficient to regulate star formation and, when combined with outflowing neutral and molecular gas, may be able to quench star formation in their host galaxies.

Population synthesis models predict that high-mass X-ray binary (HMXB) populations produced in low-metallicity environments should be more X-ray luminous, a trend supported by studies of nearby galaxies. This trend may be responsible for the observed increase of the X-ray luminosity (L X) per star formation rate (SFR) with redshift due to the decrease of metallicity (Z) at fixed stellar mass as a function of redshift. To test this hypothesis, we use a sample of 79 z ∼ 2 star-forming galaxies with oxygen abundance measurements from the MOSDEF survey, which obtained rest-frame optical spectra for ∼1500 galaxies in the CANDELS fields at 1.37 < z < 3.80. Using Chandra data from the Chandra AEGIS-X Deep, Chandra Deep Field North, and Chandra Deep Field South surveys, we stack the X-ray data at the galaxy locations in bins of redshift and Z because the galaxies are too faint to be individually detected. In agreement with previous studies, the average L X/SFR of our z ∼ 2 galaxy sample is enhanced by ≈0.4-0.8 dex relative to local HMXB L X-SFR scaling relations. Splitting our sample by Z, we find that L X/SFR and Z are anticorrelated with 97% confidence. This observed Z dependence for HMXB-dominated galaxies is consistent with both the local L X-SFR-Z relation and a subset of population synthesis models. Although the statistical significance of the observed trends is weak owing to the low X-ray statistics, these results constitute the first direct evidence connecting the redshift evolution of L X/SFR and the Z dependence of HMXBs.

We study the properties of 30 spectroscopically identified pairs of galaxies observed during the peak epoch of star formation in the universe. These systems are drawn from the MOSFIRE Deep Evolution Field (MOSDEF) Survey at 1.4 ≤ z ≤ 3.8, and are interpreted as early-stage galaxy mergers. Galaxy pairs in our sample are identified as two objects whose spectra were collected on the same Keck/MOSFIRE spectroscopic slit. Accordingly, all pairs in the sample have projected separations R proj ≤ 60 kpc. The velocity separation for pairs was required to be Δv ≤ 500 km s -1 , which is a standard threshold for defining interacting galaxy pairs at low redshift. Stellar mass ratios in our sample range from 1.1 to 550, with 12 ratios closer than or equal to 3:1, the common definition of a "major merger." Studies of merging pairs in the local universe indicate an enhancement in star formation activity and deficit in gas-phase oxygen abundance relative to isolated galaxies of the same mass. We compare the MOSDEF pairs sample to a control sample of isolated galaxies at the same redshift, finding no measurable SFR enhancement or metallicity deficit at fixed stellar mass for the pairs sample. The lack of significant difference between the average properties of pairs and control samples appears in contrast to results from low-redshift studies, although the small sample size and lower signal-to-noise of the high-redshift data limit definitive conclusions on redshift evolution. These results are consistent with some theoretical works, suggesting a reduced differential effect of precoalescence mergers on galaxy properties at high redshift - specifically that precoalescence mergers do not drive strong starbursts.

We present results from the MOSFIRE Deep Evolution Field survey on broad flux from the nebular emission lines Hα, [N ii], [O iii], Hβ, and [S ii]. The sample consists of 127 star-forming galaxies at 1.37

We use extensive spectroscopy from the MOSFIRE Deep Evolution Field survey to investigate the relationships between rest-frame optical emission line equivalent widths (W) and a number of galaxy and interstellar medium (ISM) characteristics for a sample of 1134 star-forming galaxies at redshifts 1.4 ≲ z ≲ 3.8. We examine how the equivalent widths of , , λλ4960, 5008, + Hβ, , and , depend on stellar mass, UV slope, age, star formation rate (SFR) and specific SFR (sSFR), ionization parameter and excitation conditions (O32 and /Hβ), gas-phase metallicity, and ionizing photon production efficiency (ξ ion). The trend of increasing W with decreasing stellar mass is strongest for (and +Hβ). More generally, the equivalent widths of all the lines increase with redshift at a fixed stellar mass or fixed gas-phase metallicity, suggesting that high equivalent width galaxies are common at high redshift. This redshift evolution in equivalent widths can be explained by the increase in SFR and decrease in metallicity with redshift at a fixed stellar mass. Consequently, the dependence of W on sSFR is largely invariant with redshift, particularly when examined for galaxies of a given metallicity. Our results show that high equivalent width galaxies, specifically those with high , have low stellar masses, blue UV slopes, young ages, high sSFRs, ISM line ratios indicative of high ionization parameters, high ξ ion, and low metallicities. As these characteristics are often attributed to galaxies with high ionizing escape fractions, galaxies with high W are likely candidates for the population that dominates cosmic reionization.

We investigate the nature of the relation among stellar mass, star formation rate, and gas-phase metallicity (the M∗-SFR-Z relation) at high redshifts using a sample of 260 star-forming galaxies at z∼2.3 from the MOSDEF survey. We present an analysis of the high-redshift M∗-SFR-Z relation based on several emission-line ratios for the first time. We show that a M∗-SFR-Z relation clearly exists at z∼2.3. The strength of this relation is similar to predictions from cosmological hydrodynamical simulations. By performing a direct comparison of stacks of z∼0 and z∼2.3 galaxies, we find that z∼2.3 galaxies have ∼0.1 dex lower metallicity at fixed M∗ and SFR. In the context of chemical evolution models, this evolution of the M∗-SFR-Z relation suggests an increase with redshift of the mass-loading factor at fixed M∗, as well as a decrease in the metallicity of infalling gas that is likely due to a lower importance of gas recycling relative to accretion from the intergalactic medium at high redshifts. Performing this analysis simultaneously with multiple metallicity-sensitive line ratios allows us to rule out the evolution in physical conditions (e.g., N/O ratio, ionization parameter, and hardness of the ionizing spectrum) at fixed metallicity as the source of the observed trends with redshift and with SFR at fixed M∗ at z∼2.3. While this study highlights the promise of performing high-order tests of chemical evolution models at high redshifts, detailed quantitative comparisons ultimately await a full understanding of the evolution of metallicity calibrations with redshift.

We combine Hα and Hβ spectroscopic measurements and UV photometry for a sample of 673 galaxies from the MOSDEF survey to constrain hydrogen-ionizing photon production efficiencies (ζion) at z = 1.4-2.6. We find 〈log(ζion/[s-1erg s-1Hz-1])〉=25.06(25.34), assuming the Calzetti (SMC) curve for the UV dust correction and a scatter of 0.28 dex in the ζiondistribution. After accounting for observational uncertainties and variations in dust attenuation, we conclude that the remaining scatter in ζionis likely dominated by galaxy-to-galaxy variations in stellar populations, including the slope and upper-mass cutoff of the initial mass function, stellar metallicity, star formation burstiness, and stellar evolution (e.g., single/binary star evolution). Moreover, ζionis elevated in galaxies with high ionization states (high [O iii]/[O ii]) and low oxygen abundances (low [N ii]/Hα and high [O iii]/Hβ) in the ionized ISM. However, ζiondoes not correlate with the offset from the z ∼ 0 star-forming locus in the BPT diagram, suggesting no change in the hardness of the ionizing radiation accompanying the offset from the z ∼ 0 sequence. We also find that galaxies with blue UV spectral slopes (〈β〉=-2.1) have ζionelevated by a factor of ∼2 relative to the average ζionof the sample (〈β〉=-1.4). If these blue galaxies are similar to those at z > 6, our results suggest that a lower Lyman-continuum escape fraction is required for galaxies to maintain reionization, compared to the canonical predictions from stellar population models. Furthermore, we demonstrate that even with robustly dust-corrected Hα, the UV dust attenuation can cause on average a ∼0.3 dex systematic uncertainty in calculations.

Using observations from the first 2 yr of the MOSFIRE Deep Evolution Field (MOSDEF) survey, we study 13 active galactic nucleus (AGN) driven outflows detected from a sample of 67 X-ray, IR, and/or optically selected AGNs at. The AGNs have bolometric luminosities of, including both quasars and moderate-luminosity AGNs. We detect blueshifted, ionized gas outflows in the Hβ, [O iii], Hα, and/or [N ii] emission lines of 19% of the AGNs, while only 1.8% of the MOSDEF galaxies have similarly detected outflows. The outflow velocities span ∼300 to 1000 km s-1. Eight of the 13 outflows are spatially extended on similar scales to the host galaxies, with spatial extents of 2.5-11.0 kpc. Outflows are detected uniformly across the star-forming main sequence, showing little trend with the host galaxy star formation rate. Line ratio diagnostics indicate that the outflowing gas is photoionized by the AGNs. We do not find evidence for positive AGN feedback, in either our small MOSDEF sample or a much larger Sloan Digital Sky Survey sample, using the BPT diagram. Given that a galaxy with an AGN is 10 times more likely to have a detected outflow, the outflowing gas is photoionized by the AGNs, and estimates of the mass and energy outflow rates indicate that stellar feedback is insufficient to drive at least some of these outflows; they are very likely to be AGN driven. The outflows have mass-loading factors of the order of unity, suggesting that they help regulate star formation in their host galaxies, though they may be insufficient to fully quench it.

The C iii]λλ1907, 1909 rest-frame UV emission doublet has recently been detected in galaxies during the epoch of reionization (z > 6), with a high equivalent width (EW; 10 Å, rest frame). Currently, it is possible to obtain much more detailed information for star-forming galaxies at significantly lower redshift. Accordingly, studies of their far-UV spectra are useful for understanding the factors modulating the strength of C iii] emission. We present the first statistical sample of C iii] emission measurements in star-forming galaxies at z ∼ 1. Our sample is drawn from the DEEP2 survey and spans the redshifts 0.64 z 1.35 ((z) = 1.08). We find that the median EW of individual C iii] detections in our sample (1.30 Å) is much smaller than the typical value observed thus far at z > 6. Furthermore, out of 184 galaxies with coverage of C iii], only 40 have significant detections. Galaxies with individual C iii] detections have bluer colors and lower luminosities on average than those without, implying that strong C iii] emitters are in general young and low-mass galaxies without significant dust extinction. Using stacked spectra, we further investigate how C iii] strength correlates with multiple galaxy properties (M B, U - B, M ∗, star formation rate, specific star formation rate) and rest-frame near-UV (Fe ii∗ and Mg ii) and optical ([O iii] and Hβ) emission line strengths. These results provide a detailed picture of the physical environment in star-forming galaxies at z ∼ 1, and motivate future observations of strong C iii] emitters at similar redshifts.

We present results on the variation of 7.7 μm polycyclic aromatic hydrocarbon (PAH) emission in galaxies spanning a wide range in metallicity at z ∼ 2. For this analysis, we use rest-frame optical spectra of 476 galaxies at 1.37 ≤ z ≤ 2.61 from the MOSFIRE Deep Evolution Field (MOSDEF) survey to infer metallicities and ionization states. Spitzer/MIPS 24 μm and Herschel/PACS 100 and 160 μm observations are used to derive rest-frame 7.7 μm luminosities (L7.7) and total IR luminosities (LIR), respectively. We find significant trends between the ratio of L7.7 to LIR (and to dust-corrected star formation rate [SFR]) and both metallicity and [O iii]/[O ii] (O32) emission line ratio. The latter is an empirical proxy for the ionization parameter. These trends indicate a paucity of PAH emission in low-metallicity environments with harder and more intense radiation fields. Additionally L7.7, is significantly lower in the youngest quartile of our sample (ages of ≲500 Myr) compared to older galaxies, which may be a result of the delayed production of PAHs by AGB stars. The relative strength of L7.7 to LIR is also lower by a factor of ∼2 for galaxies with masses M∗ ∼ 109.6-10.0, compared to the more massive ones. We demonstrate that commonly used conversions of (or 24 μm flux density, f 24) to underestimate the IR luminosity by more than a factor of 2 at . We adopt a mass-dependent conversion of to with = 0.09 and 0.22 for M∗ ≤ 1010 and > 1010M⊙, respectively. Based on the new scaling, the SFR-M ∗ relation has a shallower slope than previously derived. Our results also suggest a higher IR luminosity density at z ∼ 2 than previously measured, corresponding to a ∼30% increase in the SFR density.

We present results from the MOSFIRE Deep Evolution Field (MOSDEF) survey on the identification, selection biases, and host galaxy properties of 55 X-ray, IR, and optically selected active galactic nuclei (AGNs) at 1.4 < z < 3.8. We obtain rest-frame optical spectra of galaxies and AGNs and use the BPT diagram to identify optical AGNs. We examine the uniqueness and overlap of the AGNs identified at different wavelengths. There is a strong bias against identifying AGNs at any wavelength in low-mass galaxies, and an additional bias against identifying IR AGNs in the most massive galaxies. AGN hosts span a wide range of star formation rates (SFRs), similar to inactive galaxies once stellar mass selection effects are accounted for. However, we find (at ∼ 2-3σ significance) that IR AGNs are in less dusty galaxies with relatively higher SFR and optical AGNs in dusty galaxies with relatively lower SFR. X-ray AGN selection does not display a bias with host galaxy SFR. These results are consistent with those from larger studies at lower redshifts. Within star-forming galaxies, once selection biases are accounted for, we find AGNs in galaxies with similar physical properties as inactive galaxies, with no evidence for AGN activity in particular types of galaxies. This is consistent with AGNs being fueled stochastically in any star-forming host galaxy. We do not detect a significant correlation between SFR and AGN luminosity for individual AGN hosts, which may indicate the timescale difference between the growth of galaxies and their supermassive black holes.

We test for galactic conformity at 0.2 < z < 1.0 to a projected distance of 5Mpc using spectroscopic redshifts from the PRism MUlti-object Survey (PRIMUS). Our sample consists of ∼60,000 galaxies in five separate fields covering a total of ∼5.5 square degrees, which allows us to account for cosmic variance. We identify star-forming and quiescent "isolated primary" (i.e., central) galaxies using isolation criteria and cuts in specific star formation rate. We match the redshift and stellar mass distributions of these samples to control for correlations between quiescent fraction and redshift and stellar mass. We detect a significant (σ) one-halo conformity signal, or an excess of star-forming neighbors around star-forming central galaxies, of ∼5% on scales of 0-1 Mpc and a 2.5σ two-halo signal of ∼1% on scales of 1-3 Mpc. These signals are weaker than those detected in the Sloan Digital Sky Survey and are consistent with galactic conformity being the result of large-scale tidal fields and reflecting assembly bias. We also measure the star-forming fraction of central galaxies at fixed stellar mass as a function of large-scale environment and find that central galaxies are more likely to be quenched in overdense environments, independent of stellar mass. However, we find that environment does not affect the star formation efficiency of central galaxies, as long as they are forming stars. We test for redshift and stellar mass dependence of the conformity signal within our sample and show that large volumes and multiple fields are required at intermediate redshift to adequately account for cosmic variance.

We present the first statistical sample of rest-frame far-UV spectra of star-forming galaxies at z ∼ 1. These spectra are unique in that they cover the high-ionization C iv λλ1548, 1550 doublet. We also detect low-ionization features such as Si ii λ1526, Fe ii λ1608, Al ii λ1670, Ni ii λλ1741, 1751, and Si ii λ1808, and intermediate-ionization features from Al iii λλ1854, 1862. Comparing the properties of absorption lines of lower- and higher-ionization states provides a window into the multiphase nature of circumgalactic gas. Our sample is drawn from the DEEP2 survey and spans the redshift range 1.01 ≤ z ≤ 1.35 (〈z〉 = 1.25). By isolating the interstellar C iv absorption from the stellar P Cygni wind profile, we find that 69% of the C iv profiles are blueshifted with respect to the systemic velocity. Furthermore, C iv shows a small but significant blueshift relative to Fe ii (offset of the best-fit linear regression -76 ± 26 km s-1). At the same time, the C iv blueshift is on average comparable to that of Mg ii λλ2796, 2803. At this point, in explaining the larger blueshift of C iv absorption at the ∼3σ level, we cannot distinguish between the faster motion of highly ionized gas relative to gas traced by Fe ii and filling in on the red side from resonant C iv emission. We investigate how far-UV interstellar absorption kinematics correlate with other galaxy properties using stacked spectra. These stacking results show a direct link between C iv absorption and the current star formation rate, though we only observe small velocity differences among different ionization states tracing the outflowing interstellar medium.

We present Ha gas kinematics for 178 star-forming galaxies at z ∼ 2 from the MOSFIRE Deep Evolution Field survey. We have developed models to interpret the kinematic measurements from fixed-angle multi-object spectroscopy, using structural parameters derived from Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey Hubble Space Telescope/F160W imaging. For 35 galaxies, we measure resolved rotation with a median of (V/σV,0 )RE 2.1 ( s ) = . We derive dynamical masses from the kinematics and sizes and compare them to baryonic masses, with gas masses estimated from dust-corrected Ha star formation rates (SFRs) and the Kennicutt-Schmidt relation. When assuming that galaxies with and without observed rotation have the same median (V/σV,0 )RE, we find good agreement between the dynamical and baryonic masses, with a scatter of σrms = 0.34 dex and a median offset of log10 M 0.04 dex D = . This comparison implies a low dark matter fraction (8% within an effective radius) for a Chabrier initial mass function (IMF), and disfavors a Salpeter IMF. Moreover, the requirement that Mdyn/Mbaryon should be independent of inclination yields a median value of (V/σV,0 )RE = 2.1 for galaxies without observed rotation. If, instead, we treat the galaxies without detected rotation as early-type galaxies, the masses are also in reasonable agreement (δlog10 M = 0.07 dex D = - , σrms = 0.37 dex). The inclusion of gas masses is critical in this comparison; if gas masses are excluded, there is an increasing trend of Mdyn/M∗ with higher specific SFR (SSFR). Furthermore, we find indications that V s decreases with increasing Ha SSFR for our full sample, which may reflect disk settling. We also study the TullyFisher relation and find that at fixed stellar mass S0.5 0.5V2.2 + σ V2,0 2 )1/2 was higher at earlier times. At fixed baryonic mass, we observe the opposite trend. Finally, the baryonic and dynamical masses of the active galactic nuclei in our sample are also in excellent agreement, suggesting that the kinematics trace the host galaxies.

Using observations from the MOSFIRE Deep Evolution Field survey, we investigate the physical conditions of star-forming regions in z ∼ 2.3 galaxies, specifically the electron density and ionization state. From measurements of the [O ii]λλ3726,3729 and [S ii]λλ6716,6731 doublets, we find a median electron density of ∼250 cm-3 at z ∼ 2.3, an increase of an order of magnitude compared to measurements of galaxies at z ∼ 0. While z ∼ 2.3 galaxies are offset toward significantly higher O32 values relative to local galaxies at fixed stellar mass, we find that the high-redshift sample follows a similar distribution to the low-metallicity tail of the local distribution in the O32 versus R23 and O3N2 diagrams. Based on these results, we propose that z ∼ 2.3 star-forming galaxies have the same ionization parameter as local galaxies at fixed metallicity. In combination with simple photoionization models, the position of local and z ∼ 2.3 galaxies in excitation diagrams suggests that there is no significant change in the hardness of the ionizing spectrum at fixed metallicity from z ∼ 0 to z ∼ 2.3. We find that z ∼ 2.3 galaxies show no offset compared to low-metallicity local galaxies in emission line ratio diagrams involving only lines of hydrogen, oxygen, and sulfur, but show a systematic offset in diagrams involving [N ii]λ6584. We conclude that the offset of z ∼ 2.3 galaxies from the local star-forming sequence in the [N ii] BPT diagram is primarily driven by elevated N/O at fixed O/H compared to local galaxies. These results suggest that the local gas-phase and stellar metallicity sets the ionization state of star-forming regions at z ∼ 0 and z ∼ 2.

We present results on the star formation rate (SFR) versus stellar mass (M∗) relation (i.e., the "main sequence") among star-forming galaxies at 1.37 ≤ z ≤ 2.61 using the MOSFIRE Deep Evolution Field (MOSDEF) survey. Based on a sample of 261 galaxies with Hα and Hβ spectroscopy, we have estimated robust dust-corrected instantaneous SFRs over a large range in M∗ (∼109.5-1011.5 Mo). We find a correlation between log(SFR(Hα)) and log(M∗) with a slope of 0.65 ± 0.08 (0.58 ± 0.10) at 1.4 < z < 2.6 (2.1 < z < 2.6). We find that different assumptions for the dust correction, such as using the color excess of the stellar continuum to correct the nebular lines, sample selection biases against red star-forming galaxies, and not accounting for Balmer absorption, can yield steeper slopes of the log(SFR)-log(M∗) relation. Our sample is immune from these biases as it is rest-frame optically selected, Hα and Hβ are corrected for Balmer absorption, and the Hα luminosity is dust corrected using the nebular color excess computed from the Balmer decrement. The scatter of the log(SFR(Hα))-log(M∗) relation, after accounting for the measurement uncertainties, is 0.31 dex at 2.1 < z < 2.6, which is 0.05 dex larger than the scatter in log(SFR(UV))-log(M∗). Based on comparisons to a simulated SFR-M∗ relation with some intrinsic scatter, we argue that in the absence of direct measurements of galaxy-to-galaxy variations in the attenuation/extinction curves and the initial mass function, one cannot use the difference in the scatter of the SFR(Hα)- and SFR(UV)-M∗ relations to constrain the stochasticity of star formation in high-redshift galaxies.

This is the fourth paper in a series that reports on our investigation of the clustering properties of active galactic nuclei (AGNs) identified in the ROSAT All-Sky Survey and Sloan Digital Sky Survey (SDSS). In this paper we investigate the cause of the X-ray luminosity dependence of the clustering of broad-line, luminous AGNs at We fit the Hα line profile in the SDSS spectra for all X-ray and optically selected broad-line AGNs, determine the mass of the supermassive black hole (SMBH), and infer the accretion rate relative to Eddington (L/LEDD). Since MBHand L/LEDD are correlated, we create AGN subsamples in one parameter while maintaining the same distribution in the other parameter. In both the X-ray and optically selected AGN samples, we detect a weak clustering dependence with and no statistically significant dependence on L/LEDD We find a difference of up to 2.7σ when comparing the objects that belong to the 30% least and 30% most massive subsamples, in that luminous broad-line AGNs with more massive black holes reside in more massive parent dark matter halos at these redshifts. These results provide evidence that higher accretion rates in AGNs do not necessarily require dense galaxy environments, in which more galaxy mergers and interactions are expected to channel large amounts of gas onto the SMBH. We also present semianalytic models that predict a positive dependence on which is most prominent at MBH ∼ 108-9 M⊙

We report small-scale clustering measurements from the PRIsm MUlti-object Survey (PRIMUS) spectroscopic redshift survey as a function of color and luminosity. We measure the real-space cross-correlations between 62,106 primary galaxies with PRIMUS redshifts and a tracer population of ∼545,000 photometric galaxies over redshifts from z = 0.2 to z = 1. We separately fit a power-law model in redshift and luminosity to each of three independent color-selected samples of galaxies. We report clustering amplitudes at fiducial values of z = 0.5 and The clustering of the red galaxies is times as strong as that of the blue galaxies and as strong as that of the green galaxies. We also find that the luminosity dependence of the clustering is strongly dependent on physical scale, with greater luminosity dependence being found between and , compared to the to range. Moreover, over a range of two orders of magnitude in luminosity, a single power-law fit to the luminosity dependence is not sufficient to explain the increase in clustering at both the bright and faint ends at the smaller scales. We argue that luminosity-dependent clustering at small scales is a necessary component of galaxy-halo occupation models for blue, star-forming galaxies as well as for red, quenched galaxies.

We utilize ΛCDM halo occupation models of galaxy clustering to investigate the evolving stellar mass dependent clustering of galaxies in the PRIsm MUlti-object Survey (PRIMUS) and DEEP2 Redshift Survey over the past eight billion years of cosmic time, between 0.2 < z < 1.2. These clustering measurements provide new constraints on the connections between dark matter halo properties and galaxy properties in the context of the evolving largescale structure of the universe. Using both an analytic model and a set of mock galaxy catalogs, we find a strong correlation between central galaxy stellar mass and dark matter halo mass over the range Mhalo ∼ 10111013 h-1 M⊙, approximately consistent with previous observations and theoretical predictions. However, the stellarto-halo mass relation and the mass scale where star formation efficiency reaches a maximum appear to evolve more strongly than predicted by other models, including models based primarily on abundance-matching constraints. We find that the fraction of satellite galaxies in halos of a given mass decreases significantly from z ∼ 0.5 to z ∼ 0.9, partly due to the fact that halos at fixed mass are rarer at higher redshift and have lower abundances. We also find that the M1/Mmin ratio, a model parameter that quantifies the critical mass above which halos host at least one satellite, decreases from ≈20 at z ∼ 0 to ≈13 at z ∼ 0.9. Considering the evolution of the subhalo mass function vis-à-vis satellite abundances, this trend has implications for relations between satellite galaxies and halo substructures and for intracluster mass, which we argue has grown due to stripped and disrupted satellites between z ∼ 0.9 and z ∼ 0.5.

In this paper we present the MOSFIRE Deep Evolution Field (MOSDEF) survey. The MOSDEF survey aims to obtain moderate-resolution (R = 3000-3650) rest-frame optical spectra (∼3700-7000 ) for ∼1500 galaxies at in three well-studied CANDELS fields: AEGIS, COSMOS, and GOODS-N. Targets are selected in three redshift intervals:, down to fixed (F160W) magnitudes of 24.0, 24.5, and 25.0, respectively, using the photometric and spectroscopic catalogs from the 3D-HST survey. We target both strong nebular emission lines (e.g., [O ii], Hβ, [O iii], H, [N ii], and [S ii]) and stellar continuum and absorption features (e.g., Balmer lines, Ca-ii H and K, Mgb, 4000 break). Here we present an overview of our survey, the observational strategy, the data reduction and analysis, and the sample characteristics based on spectra obtained during the first 24 nights. To date, we have completed 21 masks, obtaining spectra for 591 galaxies. For ∼80% of the targets we derive a robust redshift from either emission or absorption lines. In addition, we confirm 55 additional galaxies, which were serendipitously detected. The MOSDEF galaxy sample includes unobscured star-forming, dusty star-forming, and quiescent galaxies and spans a wide range in stellar mass () and star formation rate. The spectroscopically confirmed sample is roughly representative of an H-band limited galaxy sample at these redshifts. With its large sample size, broad diversity in galaxy properties, and wealth of available ancillary data, MOSDEF will transform our understanding of the stellar, gaseous, metal, dust, and black hole content of galaxies during the time when the universe was most active.

We present results on the dust attenuation curve of z ∼ 2 galaxies using early observations from the MOSFIRE Deep Evolution Field survey. Our sample consists of 224 star-forming galaxies with zspec = 1.36-2.59 and high signal-to-noise ratio measurements of Hα and Hβ obtained with Keck/MOSFIRE. We construct composite spectral energy distributions (SEDs) of galaxies in bins of Balmer decrement to measure the attenuation curve. We find a curve that is similar to the SMC extinction curve at λ ≳ 2500 Å. At shorter wavelengths, the shape is identical to that of the Calzetti et al. relation, but with a lower normalization. Hence, the new attenuation curve results in star formation rates (SFRs) that are ≈20% lower, and stellar masses that are Δ log(M∗/M⊙) ≃ 0.16 dex lower, than those obtained with the Calzetti relation. We find that the difference in the total attenuation of the ionized gas and stellar continuum correlates strongly with SFR, such that for dust-corrected SFRs ≳ 20 Mȯ yr-1, assuming a Chabrier initial mass function, the nebular emission lines suffer an increasing degree of obscuration relative to the continuum. A simple model that can account for these trends is one in which the UV through optical stellar continuum is dominated by a population of less-reddened stars, while the nebular line and bolometric luminosities become increasingly dominated by dustier stellar populations for galaxies with large SFRs, as a result of the increased dust enrichment that accompanies such galaxies. Consequently, UV- and SED-based SFRs may underestimate the total SFR at even modest levels of ≈20 Mȯ yr-1.

We investigate the effects of galaxy environment on the evolution of the quiescent fraction (fQ) from z = 0.8 to 0.0 using spectroscopic redshifts and multi-wavelength imaging data from the PRIsm MUlti-object Survey (PRIMUS) and the Sloan Digital Sky Survey (SDSS). Our stellar mass limited galaxy sample consists of ∼14,000 PRIMUS galaxies within z = 0.2-0.8 and ∼64,000 SDSS galaxies within z = 0.05-0.12. We classify the galaxies as quiescent or star-forming (SF) based on an evolving specific star formation cut, and as low or high density environments based on fixed cylindrical aperture environment measurements on a volume-limited environment defining population. For quiescent and SF galaxies in low or high density environments, we examine the evolution of their stellar mass function (SMF). Then using the SMFs we compute fQ (M∗) and quantify its evolution within our redshift range. We find that the quiescent fraction is higher at higher masses and in denser environments. The quiescent fraction rises with cosmic time for all masses and environments. At a fiducial mass of 1010.5 M⊙, from z ∼ 0.7 to 0.1, the quiescent fraction rises by 15% at the lowest environments and by 25% at the highest environments we measure. These results suggest that for a minority of galaxies their cessation of star formation is due to external influences on them. In other words, in the recent universe a substantial fraction of the galaxies that cease forming stars do so due to internal processes.

We study the evidence for a connection between active galactic nuclei (AGNs) fueling and star formation by investigating the relationship between the X-ray luminosities of AGNs and the star formation rates (SFRs) of their host galaxies. We identify a sample of 309 AGNs with 1041 < LX < 1044 erg s-1 at 0.2 < z < 1.2 in the PRIMUS redshift survey. We find AGNs in galaxies with a wide range of SFR at a given LX. We do not find a significant correlation between SFR and the observed instantaneous LX for star-forming AGN host galaxies. However, there is a weak but significant correlation between the mean LX and SFR of detected AGNs in star-forming galaxies, which likely reflects that LX varies on shorter timescales than SFR. We find no correlation between stellar mass and LX within the AGN population. Within both populations of star-forming and quiescent galaxies, we find a similar power-law distribution in the probability of hosting an AGN as a function of specific accretion rate. Furthermore, at a given stellar mass, we find a star-forming galaxy ∼2-3 more likely than a quiescent galaxy to host an AGN of a given specific accretion rate. The probability of a galaxy hosting an AGN is constant across the main sequence of star formation. These results indicate that there is an underlying connection between star formation and the presence of AGNs, but AGNs are often hosted by quiescent galaxies.

We present results on the excitation properties of z ∼ 2.3 galaxies using early observations from the MOSFIRE Deep Evolution Field (MOSDEF) Survey. With its coverage of the full suite of strong rest-frame optical emission lines, MOSDEF provides an unprecedented view of the rest-frame optical spectra of a representative sample of distant star-forming galaxies. We investigate the locations of z ∼ 2.3 MOSDEF galaxies in multiple emission-line diagnostic diagrams. These include the [O iii]λ5007/Hβ vs. [N ii]/Hα and [O iii]λ5007/Hβ vs. [S ii]λλ6717, 6731/Hα "BPT" diagrams, as well as the O32 vs. R23 excitation diagram. We recover the well-known offset in the star-forming sequence of high-redshift galaxies in the [O iii]λ5007/Hβ vs. [N ii]/Hα BPT diagram relative to Sloan Digital Sky Survey star-forming galaxies. However, the shift for our rest-frame optically selected sample is less significant than for rest-frame-UV selected and emission-line selected galaxies at z ∼ 2. Furthermore, we find that the offset is mass-dependent, only appearing within the low-mass half of the z ∼ 2.3 MOSDEF sample, where galaxies are shifted toward higher [N ii]/Hα at fixed [O iii]/Hβ. Within the [O iii]λ5007/Hβ vs. [S ii]/Hα and O32 vs. R23 diagrams, we find that z ∼ 2.3 galaxies are distributed like local ones, and therefore attribute the shift in the [O iii]λ5007/Hβ vs. [N ii]/Hα BPT diagram to elevated N/O abundance ratios among lower-mass () high-redshift galaxies. The variation in N/O ratios calls into question the use at high redshift of oxygen abundance indicators based on nitrogen lines, but the apparent invariance with redshift of the excitation sequence in the O32 vs. R23 diagram paves the way for using the combination of O32 and R23 as an unbiased metallicity indicator over a wide range in redshift. This indicator will allow for an accurate characterization of the shape and normalization of the mass-metallicity relationship over more than 10 Gyr.

We present results from the MOSFIRE Deep Evolution Field (MOSDEF) survey on rest-frame optical active galactic nucleus (AGN) identification and completeness at z ∼ 2.3. With our sample of 50 galaxies and 10 X-ray and IR-selected AGNs with measured Hβ, [O III], Hα, and N II emission lines, we investigate the location of AGNs in the BPT, MEx (mass-excitation), and CEx (color-excitation) diagrams. We find that th BPT diagram works well to identify AGNs at z ∼ 2.3 and that the z ∼ 0 AGN/star-forming galaxy classifications do not need to shift substantially at z ∼ 2.3 to robustly separate these populations. However, the MEx diagram fails to identify all of the AGN identified in the BPT diagram, and the CEx diagram is substantially contaminated at high redshift. We further show that AGN samples selected using the BPT diagram have selection biases in terms of both host stellar mass and stellar population, in that AGNs in low mass and/or high specific star formation rate galaxies are difficult to identify using the BPT diagram. These selection biases become increasingly severe at high redshift, such that optically selected AGN samples at high redshift will necessarily be incomplete. We also find that the gas in the narrow-line region appears to be more enriched than gas in the host galaxy for at least some MOSDEF AGNs. However, AGNs at z ∼ 2 are generally less enriched than local AGNs with the same host stellar mass.

We present results on the z ∼ 2.3 mass-metallicity relation (MZR) using early observations from the MOSFIRE Deep Evolution Field survey. We use an initial sample of 87 star-forming galaxies with spectroscopic coverage of Hβ, [OIII] λ5007, Hα, and [NII] λ6584 rest-frame optical emission lines, and estimate the gas-phase oxygen abundance based on the N2 and O3N2 strong-line indicators. We find a positive correlation between stellar mass and metallicity among individual z ∼ 2.3 galaxies using both the N2 and O3N2 indicators. We also measure the emission-line ratios and corresponding oxygen abundances for composite spectra in bins of stellar mass. Among composite spectra, we find a monotonic increase in metallicity with increasing stellar mass, offset ∼0.15-0.3 dex below the local MZR. When the sample is divided at the median star-formation rate (SFR), we do not observe significant SFR dependence of the z ∼ 2.3 MZR among either individual galaxies or composite spectra. We furthermore find that z ∼ 2.3 galaxies have metallicities ∼0.1 dex lower at a given stellar mass and SFR than is observed locally. This offset suggests that high-redshift galaxies do not fall on the local "fundamental metallicity relation" among stellar mass, metallicity, and SFR, and may provide evidence of a phase of galaxy growth in which the gas reservoir is built up due to inflow rates that are higher than star-formation and outflow rates. However, robust conclusions regarding the gas-phase oxygen abundances of high-redshift galaxies await a systematic reappraisal of the application of locally calibrated metallicity indicators at high redshift.

We present the results of a combined galaxy population analysis for the host galaxies of active galactic nuclei (AGN) identified at 0 < z < 1.4 within the Sloan Digital Sky Survey, Boötes, and DEEP2 surveys. We identified AGN in a uniform and unbiased manner at X-ray, infrared, and radio wavelengths. Supermassive black holes undergoing radiatively efficient accretion (detected as X-ray and/or infrared AGN) appear to be hosted in a separate and distinct galaxy population than AGN undergoing powerful mechanically dominated accretion (radio AGN). Consistent with some previous studies, radiatively efficient AGN appear to be preferentially hosted in modest star-forming galaxies, with little dependence on AGN or galaxy luminosity. AGN exhibiting radio-emitting jets due to mechanically dominated accretion are almost exclusively observed in massive, passive galaxies. Crucially, we now provide strong evidence that the observed host-galaxy trends are independent of redshift. In particular, these different accretion-mode AGN have remained as separate galaxy populations throughout the last 9 Gyr. Furthermore, it appears that galaxies hosting AGN have evolved along the same path as galaxies that are not hosting AGN with little evidence for distinctly separate evolution. © 2014. The American Astronomical Society. All rights reserved.

We present an observationally motivated model to connect the active galactic nucleus (AGN) and galaxy populations at 0.2 < z < 1.0 and predict the AGN X-ray luminosity function (XLF). We start with measurements of the stellar mass function of galaxies (from the Prism Multi-object Survey) and populate galaxies with AGNs using models for the probability of a galaxy hosting an AGN as a function of specific accretion rate. Our model is based on measurements indicating that the specific accretion rate distribution is a universal function across a wide range of host stellar masses with slope γ1 -0.65 and an overall normalization that evolves with redshift. We test several simple assumptions to extend this model to high specific accretion rates (beyond the measurements) and compare the predictions for the XLF with the observed data. We find good agreement with a model that allows for a break in the specific accretion rate distribution at a point corresponding to the Eddington limit, a steep power-law tail to super-Eddington ratios with slope , and a scatter of 0.38 dex in the scaling between black hole and host stellar mass. Our results show that samples of low luminosity AGNs are dominated by moderately massive galaxies () growing with a wide range of accretion rates due to the shape of the galaxy stellar mass function rather than a preference for AGN activity at a particular stellar mass. Luminous AGNs may be a severely skewed population with elevated black hole masses relative to their host galaxies and in rare phases of rapid accretion. © 2013. The American Astronomical Society. All rights reserved.

We describe the design and data analysis of the DEEP2 Galaxy Redshift Survey, the densest and largest high-precision redshift survey of galaxies at z ∼ 1 completed to date. The survey was designed to conduct a comprehensive census of massive galaxies, their properties, environments, and large-scale structure down to absolute magnitude MB = -20 at z ∼ 1 via ∼90 nights of observation on the Keck telescope. The survey covers an area of 2.8 deg2 divided into four separate fields observed to a limiting apparent magnitude of RAB = 24.1. Objects with z ≲ 0.7 are readily identifiable using BRI photometry and rejected in three of the four DEEP2 fields, allowing galaxies with z > 0.7 to be targeted ∼2.5 times more efficiently than in a purely magnitude-limited sample. Approximately 60% of eligible targets are chosen for spectroscopy, yielding nearly 53,000 spectra and more than 38,000 reliable redshift measurements. Most of the targets that fail to yield secure redshifts are blue objects that lie beyond z ∼ 1.45, where the [O II] 3727 Å doublet lies in the infrared. The DEIMOS 1200 line mm-1 grating used for the survey delivers high spectral resolution (R ∼ 6000), accurate and secure redshifts, and unique internal kinematic information. Extensive ancillary data are available in the DEEP2 fields, particularly in the Extended Groth Strip, which has evolved into one of the richest multiwavelength regions on the sky. This paper is intended as a handbook for users of the DEEP2 Data Release 4, which includes all DEEP2 spectra and redshifts, as well as for the DEEP2 DEIMOS data reduction pipelines. Extensive details are provided on object selection, mask design, biases in target selection and redshift measurements, the spec2d two-dimensional data-reduction pipeline, the spec1d automated redshift pipeline, and the zspec visual redshift verification process, along with examples of instrumental signatures or other artifacts that in some cases remain after data reduction. Redshift errors and catastrophic failure rates are assessed through more than 2000 objects with duplicate observations. Sky subtraction is essentially photon-limited even under bright OH sky lines; we describe the strategies that permitted this, based on high image stability, accurate wavelength solutions, and powerful B-spline modeling methods. We also investigate the impact of targets that appear to be single objects in ground-based targeting imaging but prove to be composite in Hubble Space Telescope data; they constitute several percent of targets at z ∼ 1, approaching ∼5%-10% at z > 1.5. Summary data are given that demonstrate the superiority of DEEP2 over other deep high-precision redshift surveys at z ∼ 1 in terms of redshift accuracy, sample number density, and amount of spectral information. We also provide an overview of the scientific highlights of the DEEP2 survey thus far. © 2013. The American Astronomical Society. All rights reserved.

We present a study of the prevalence, strength, and kinematics of ultraviolet Fe II and Mg II emission lines in 212 star-forming galaxies at z 1 selected from the DEEP2 survey. We find Fe II* emission in composite spectra assembled on the basis of different galaxy properties, indicating that Fe II* emission is common at z 1. In these composites, Fe II* emission is observed at roughly the systemic velocity. At z 1, we find that the strength of Fe II* emission is most strongly modulated by dust attenuation, and is additionally correlated with redshift, star formation rate, and [O II] equivalent width, such that systems at higher redshifts with lower dust levels, lower star formation rates, and larger [O II] equivalent widths show stronger Fe II* emission. We detect Mg II emission in at least 15% of the individual spectra and we find that objects showing stronger Mg II emission have higher specific star formation rates, smaller [O II] linewidths, larger [O II] equivalent widths, lower dust attenuations, and lower stellar masses than the sample as a whole. Mg II emission strength exhibits the strongest correlation with specific star formation rate, although we find evidence that dust attenuation and stellar mass also play roles in the regulation of Mg II emission. Future integral field unit observations of the spatial extent of Fe II* and Mg II emission in galaxies with high specific star formation rates, low dust attenuations, and low stellar masses will be important for probing the morphology of circumgalactic gas. © 2013. The American Astronomical Society. All rights reserved..

We develop empirical methods for modeling the galaxy population and populating cosmological N-body simulations with mock galaxies according to the observed properties of galaxies in survey data. We use these techniques to produce a new set of mock catalogs for the DEEP2 Galaxy Redshift Survey based on the output of the high-resolution Bolshoi simulation, as well as two other simulations with different cosmological parameters, all of which we release for public use. The mock-catalog creation technique uses subhalo abundance matching to assign galaxy luminosities to simulated dark-matter halos. It then adds color information to the resulting mock galaxies in a manner that depends on the local galaxy density, in order to reproduce the measured color-environment relation in the data. In the course of constructing the catalogs, we test various models for including scatter in the relation between halo mass and galaxy luminosity, within the abundance-matching framework. We find that there is no constant-scatter model that can simultaneously reproduce both the luminosity function and the autocorrelation function of DEEP2. This result has implications for galaxy-formation theory, and it restricts the range of contexts in which the mock catalogs can be usefully applied. Nevertheless, careful comparisons show that our new mock catalogs accurately reproduce a wide range of the other properties of the DEEP2 catalog, suggesting that they can be used to gain a detailed understanding of various selection effects in DEEP2. © 2013. The American Astronomical Society. All rights reserved.