The MOSDEF Survey: The Metallicity Dependence of X-Ray Binary Populations at z ∼ 2

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

Kiadói és nyomdai tevékenység a szerbek körében a középkor végén és az újkor hajnalán

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

The MOSDEF Survey: Significant Evolution in the Rest-frame Optical Emission Line Equivalent Widths of Star-forming Galaxies at z = 1.4-3.8

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

The mosdef survey: A census of agn-driven ionized outflows at z = 1.4-3.8

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

WT1 and GATA4 in the regulation of sex-specific gonadal gene expression.

<p>During testis development, WT1 is required for activating various testis promoting genes, i.e. <i>Amh</i>, <i>Amhr2</i>, <i>Nr5a1</i>(<i>Sf1)</i>, <i>Star</i>, <i>Sox9</i>, <i>Gli1</i>, <i>Gli2</i>, <i>Smo</i>, <i>Dhh and Ptch1</i>. GATA4 represses ovarian promoting transcripts such as <i>Ctnnb1</i>, <i>Bmp2</i>, and <i>Fst</i>, in the testis, and thereby may be essential for the maintenance of the testis phenotype. GATA4 is also involved in repressing <i>Dhh</i> and <i>Ptch1</i> transcript levels in embryonic testis, which may contribute to the fine-tuning of their threshold levels. Given such a pivotal role of GATA4, it is likely that sufficient GATA4 levels are ensured by a back-up mechanism provided by the GATA4 E1b isoform in the testis. During ovary development, i.e. in the absence of SRY, WNT4 and RSPO-1 levels are stabilized and promote canonical Wnt signaling. In the ovary, WT1 is required for <i>Dax1</i> expression. GATA4 acts as a repressor of <i>Ctnnb1</i> and serves as an activator for the transcripts <i>Gli2</i>, <i>Gli3</i>, and <i>Smo</i>, the latter of which may be regulated synergistically by both WT1 and GATA4. WT1 and GATA4 may also synergize on <i>Foxl2</i> transcription, which contributes to an ovarian specific signature. Suggested stimulatory (→) and inhibitory (⊥) pathways identified herein are marked in red color.</p

The MOSDEF Survey: Stellar Continuum Spectra and Star Formation Histories of Active, Transitional, and Quiescent Galaxies at 1.4 &lt; z &lt; 2.6

Using the MOSFIRE Deep Evolution Field (MOSDEF) rest-frame optical spectroscopic survey, we investigate the star formation histories (SFHs) of different galaxy types, ranging from actively star-forming to quiescent at 1.4 ≤ z ≤ 2.6. SFHs are constrained utilizing stellar continuum spectroscopy, specifically through a combination of Balmer absorption lines, the 4000 Å break, and the equivalent width of the Hα emission line. To attain a sufficiently high signal-to-noise ratio (S/N) to conduct these measurements we stack spectra of galaxies with similar spectral types, as determined from their rest-frame U - V and V - J colors. We bin the MOSDEF sample into five spectral types, subdividing the quiescent and star-forming bins to better explore galaxies transitioning between the two. We constrain the average SFHs for each type, finding that quiescent and transitional galaxies in the MOSDEF sample are dominated by an SFH with an average star formation timescale of τ ∼ 0.1-0.2 Gyr. These findings contrast with measurements from the low-redshift Universe where, on average, galaxies form their stars over a more extended time period (τ &gt; 1 Gyr). Furthermore, our spectral index measurements correlate with mass surface density for all spectral types. Finally, we compare the average properties of the galaxies in our transitional bins to investigate possible paths to quiescence, and speculate on the viability of a dusty post-starburst phase

The MOSDEF Survey: No Significant Enhancement in Star Formation or Deficit in Metallicity in Merging Galaxy Pairs at 1.5 ≲ z ≲ 3.5

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

The MOSDEF Survey: A Stellar Mass-SFR-Metallicity Relation Exists at z ∼ 2.3

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