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  • 1
    Online Resource
    Online Resource
    American Astronomical Society ; 2020
    In:  The Astrophysical Journal Letters Vol. 903, No. 2 ( 2020-11-01), p. L28-
    In: The Astrophysical Journal Letters, American Astronomical Society, Vol. 903, No. 2 ( 2020-11-01), p. L28-
    Abstract: We use a sample of star-forming field and protocluster galaxies at z  = 2.0–2.5 with Keck/MOSFIRE K -band spectra, a wealth of rest-frame ultraviolet (UV) photometry, and Spitzer/MIPS and Herschel/PACS observations, to dissect the relation between the ratio of infrared (IR) to UV luminosity (IRX) versus UV slope ( β ) as a function of gas-phase metallicity (  ∼ 8.2–8.7). We find no significant dependence of the IRX- β trend on environment. However, we find that at a given β , IRX is highly correlated with metallicity, and less correlated with mass, age, and specific star formation rate (sSFR). We conclude that, of the physical properties tested here, metallicity is the primary physical cause of the IRX- β scatter, and the IRX correlation with mass is presumably due to the mass dependence on metallicity. Our results indicate that the UV attenuation curve steepens with decreasing metallicity, and spans the full range of slope possibilities from a shallow Calzetti-type curve for galaxies with the highest metallicity in our sample (  ∼ 8.6) to a steep Small Magellanic Cloud (SMC)-like curve for those with  ∼ 8.3. Using a Calzetti (SMC) curve for the low (high) metallicity galaxies can lead to up to a factor of 3 overestimation (underestimation) of the UV attenuation and obscured star formation rate. We speculate that this change is due to different properties of dust grains present in the interstellar medium of low- and high-metallicity galaxies.
    Type of Medium: Online Resource
    ISSN: 2041-8205 , 2041-8213
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2020
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 2006858-X
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  • 2
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 526, No. 1 ( 2023-09-21), p. 1512-1527
    Abstract: The $\rm {H}\alpha$-to-UV luminosity ratio ($L(\text{H}\alpha)/L(\rm UV)$) is often used to probe bursty star formation histories (SFHs) of star-forming galaxies and it is important to validate it against other proxies for burstiness. To address this issue, we present a statistical analysis of the resolved distribution of star formation rate surface density (ΣSFR) as well as stellar age and their correlations with the globally measured $L(\text{H}\alpha)/L(\rm UV)$ for a sample of 310 star-forming galaxies in two redshift bins of 1.37 & lt; z & lt; 1.70 and 2.09 & lt; z & lt; 2.61 observed by the MOSFIRE Deep Evolution Field (MOSDEF) survey. We use the multiwaveband CANDELS/3D-HST imaging of MOSDEF galaxies to construct ΣSFR and stellar age maps. We analyse the composite rest-frame far-ultraviolet spectra of a subsample of MOSFIRE Deep Evolution Field (MOSDEF) targets obtained by the Keck Low Resolution Imager and Spectrometer (LRIS), which includes 124 star-forming galaxies (MOSDEF-LRIS) at redshifts 1.4 & lt; z & lt; 2.6, to examine the average stellar population properties, and the strength of age-sensitive far-ultraviolet spectral features in bins of $L(\text{H}\alpha)/L(\rm UV)$. Our results show no significant evidence that individual galaxies with higher $L(\text{H}\alpha)/L(\rm UV)$ are undergoing a burst of star formation based on the resolved distribution of ΣSFR of individual star-forming galaxies. We segregate the sample into subsets with low and high $L(\text{H}\alpha)/L(\rm UV)$. The high-$L(\text{H}\alpha)/L(\rm UV)$ subset exhibits, on average, an age of $\log [\rm {Age/yr}]$ = 8.0, compared to $\log [\rm {Age/yr}] $ = 8.4 for the low-$L(\text{H}\alpha)/L(\rm UV)$ galaxies, though the difference in age is significant at only the 2σ level. Furthermore, we find no variation in the strengths of Si iv λλ1393, 1402 and C iv λλ1548, 1550 P-Cygni features from massive stars between the two subsamples, suggesting that the high-$L(\text{H}\alpha)/L(\rm UV)$ galaxies are not preferentially undergoing a burst compared to galaxies with lower $L(\text{H}\alpha)/L(\rm UV)$. On the other hand, we find that the high-$L(\text{H}\alpha)/L(\rm UV)$ galaxies exhibit, on average, more intense He ii λ1640 emission, which may possibly suggest the presence of a higher abundance of high-mass X-ray binaries.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 2016084-7
    SSG: 16,12
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  • 3
    Online Resource
    Online Resource
    American Astronomical Society ; 2021
    In:  The Astrophysical Journal Vol. 910, No. 1 ( 2021-03-01), p. 57-
    In: The Astrophysical Journal, American Astronomical Society, Vol. 910, No. 1 ( 2021-03-01), p. 57-
    Abstract: We study the mass–metallicity relation for 19 members of a spectroscopically confirmed protocluster in the COSMOS field at z = 2.2 (CC2.2), and compare it with that of 24 similarly selected field galaxies at the same redshift. Both samples are H α emitting sources, chosen from the HiZELS narrowband survey, with metallicities derived from the N 2 [ NII ] λ 6584 H α line ratio. For the mass-matched samples of protocluster and field galaxies, we find that protocluster galaxies with 10 9.9 M ⊙ ≤ M * ≤ 10 10.9 M ⊙ are metal deficient by 0.10 ± 0.04 dex (2.5 σ significance) compared to their coeval field galaxies. This metal deficiency is absent for low-mass galaxies, M * 〈 10 9.9 M ⊙ . Moreover, relying on both spectral energy distribution derived and H α (corrected for dust extinction based on M * ) star formation rates (SFRs), we find no strong environmental dependence of the SFR– M * relation; however, we are not able to rule out the existence of small dependence due to inherent uncertainties in both SFR estimators. The existence of 2.5 σ significant metal deficiency for massive protocluster galaxies favors a model in which funneling of the primordial cold gas through filaments dilutes the metal content of protoclusters at high redshifts ( z ≳ 2). At these redshifts, gas reservoirs in filaments are dense enough to cool down rapidly and fall into the potential well of the protocluster to lower the gas-phase metallicity of galaxies. Moreover, part of this metal deficiency could be originated from galaxy interactions that are more prevalent in dense environments.
    Type of Medium: Online Resource
    ISSN: 0004-637X , 1538-4357
    RVK:
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2021
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 1473835-1
    SSG: 16,12
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  • 4
    In: The Astrophysical Journal, American Astronomical Society, Vol. 942, No. 1 ( 2023-01-01), p. 36-
    Abstract: We present the first comprehensive release of photometric redshifts (photo - z 's) from the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS) team. We use statistics based upon the Quantile–Quantile ( Q – Q ) plot to identify biases and signatures of underestimated or overestimated errors in photo - z probability density functions (PDFs) produced by six groups in the collaboration; correcting for these effects makes the resulting PDFs better match the statistical definition of a PDF. After correcting each group’s PDF, we explore three methods of combining the different groups’ PDFs for a given object into a consensus curve. Two of these methods are based on identifying the minimum f -divergence curve, i.e., the PDF that is closest in aggregate to the other PDFs in a set (analogous to the median of an array of numbers). We demonstrate that these techniques yield improved results using sets of spectroscopic redshifts independent of those used to optimize PDF modifications. The best photo - z PDFs and point estimates are achieved with the minimum f -divergence using the best four PDFs for each object (mFDa4) and the hierarchical Bayesian (HB4) methods, respectively. The HB4 photo - z point estimates produced σ NMAD = 0.0227/0.0189 and ∣Δ z /(1 + z )∣ 〉 0.15 outlier fraction = 0.067/0.019 for spectroscopic and 3D Hubble Space Telescope redshifts, respectively. Finally, we describe the structure and provide guidance for the use of the CANDELS photo - z catalogs, which are available at https://archive.stsci.edu/prepds/candels/ .
    Type of Medium: Online Resource
    ISSN: 0004-637X , 1538-4357
    RVK:
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2023
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 1473835-1
    SSG: 16,12
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  • 5
    In: The Astrophysical Journal, American Astronomical Society, Vol. 908, No. 2 ( 2021-02-01), p. 120-
    Abstract: Using the near-IR spectroscopy of the MOSFIRE Deep Evolution Field survey, we investigate the role of the local environment in the gas-phase metallicity of galaxies. The local environment measurements are derived from accurate and uniformly calculated photometric redshifts with well-calibrated probability distributions. Based on rest-frame optical emission lines, [N ii ] λ 6584 and H α , we measure gas-phase oxygen abundances of 167 galaxies at 1.37 ≤ z ≤ 1.7 and 303 galaxies at 2.09 ≤ z ≤ 2.61, located in diverse environments. We find that at z ∼ 1.5, the average metallicity of galaxies in overdensities with M * ∼ 10 9.8 M ⊙ , 10 10.2 M ⊙, and 10 10.8 M ⊙ is higher relative to their field counterparts by 0.094 ± 0.051, 0.068 ± 0.028, and 0.052 ± 0.043 dex, respectively. However, this metallicity enhancement does not exist at higher redshift, z ∼ 2.3, where, compared to the field galaxies, we find 0.056 ± 0.043, 0.056 ± 0.028, and 0.096 ± 0.034 dex lower metallicity for galaxies in overdense environments with M * ∼ 10 9.8 M ⊙ , 10 10.2 M ⊙ and 10 10.7 M ⊙ , respectively. Our results suggest that, at 1.37 ≤ z ≤ 2.61, the variation of mass–metallicity relation with local environment is small ( 〈 0.1 dex), and reverses at z ∼ 2. Our results support the hypothesis that, at the early stages of cluster formation, owing to efficient gas cooling, galaxies residing in overdensities host a higher fraction of pristine gas with prominent primordial gas accretion, which lowers their gas-phase metallicity compared to their coeval field galaxies. However, as the universe evolves to lower redshifts ( z ≲ 2), the shock-heated gas in overdensities cannot cool down efficiently, and galaxies become metal-rich rapidly due to the suppression of pristine gas inflow and re-accretion of metal-enriched outflows in overdensities.
    Type of Medium: Online Resource
    ISSN: 0004-637X , 1538-4357
    RVK:
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2021
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 1473835-1
    SSG: 16,12
    Library Location Call Number Volume/Issue/Year Availability
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  • 6
    In: The Astrophysical Journal, American Astronomical Society, Vol. 970, No. 2 ( 2024-08-01), p. 188-
    Abstract: We use the Ultraviolet Imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey fields (UVCANDELS) to measure half-light radii in the rest-frame far-UV for ∼16,000 disk-like galaxies over 0.5 ≤ z ≤ 3. We compare these results to rest-frame optical sizes that we measure in a self-consistent way and find that the stellar mass–size relation of disk galaxies is steeper in the rest-frame UV than in the optical across our entire redshift range. We show that this is mainly driven by massive galaxies (≳10 10 M ⊙ ), which we find to also be among the most dusty. Our results are consistent with the literature and have commonly been interpreted as evidence of inside-out growth wherein galaxies form their central structures first. However, they could also suggest that the centers of massive galaxies are more heavily attenuated than their outskirts. We distinguish between these scenarios by modeling and selecting galaxies at z = 2 from the VELA simulation suite in a way that is consistent with UVCANDELS. We show that the effects of dust alone can account for the size differences we measure at z = 2. This indicates that, at different wavelengths, size differences and the different slopes of the stellar mass–size relation do not constitute evidence for inside-out growth.
    Type of Medium: Online Resource
    ISSN: 0004-637X , 1538-4357
    RVK:
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2024
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 1473835-1
    SSG: 16,12
    Library Location Call Number Volume/Issue/Year Availability
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  • 7
    In: The Astrophysical Journal, American Astronomical Society, Vol. 943, No. 2 ( 2023-02-01), p. 82-
    Abstract: Atacama Large Millimeter/submillimeter Array (ALMA) observations of the long-wavelength dust continuum are used to estimate the gas masses in a sample of 708 star-forming galaxies at z = 0.3−4.5. We determine the dependence of gas masses and star formation efficiencies (SFEs; SFR per unit gas mass) on redshift (z), M * , and star formation rate (SFR) relative to the main sequence (MS). We find that 70% of the increase in SFRs of the MS is due to the increased gas masses at earlier epochs, while 30% is due to increased efficiency of star formation (SF). For galaxies above the MS this is reversed—with 70% of the increased SFR relative to the MS being due to elevated SFEs. Thus, the major evolution of star formation activity at early epochs is driven by increased gas masses, while the starburst activity taking galaxies above the MS is due to enhanced triggering of star formation (likely due to galactic merging). The interstellar gas peaks at z = 2 and dominates the stellar mass down to z = 1.2. Accretion rates needed to maintain continuity of the MS evolution reach 〉 100 M ⊙ yr −1 at z 〉 2. The galactic gas contents are likely the driving determinant for both the rise in SF and AGN activity from z = 5 to their peak at z = 2 and subsequent fall at lower z . We suggest that for self-gravitating clouds with supersonic turbulence, cloud collisions and the filamentary structure of the clouds regulate the star formation activity.
    Type of Medium: Online Resource
    ISSN: 0004-637X , 1538-4357
    RVK:
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2023
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 1473835-1
    SSG: 16,12
    Library Location Call Number Volume/Issue/Year Availability
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  • 8
    In: The Astrophysical Journal, American Astronomical Society, Vol. 942, No. 2 ( 2023-01-01), p. 91-
    Abstract: We present a new method based on information theory to find the optimal number of bands required to measure the physical properties of galaxies with desired accuracy. As a proof of concept, using the recently updated COSMOS catalog (COSMOS2020), we identify the most relevant wave bands for measuring the physical properties of galaxies in a Hawaii Two-0- (H20) and UVISTA-like survey for a sample of i 〈 25 AB mag galaxies. We find that with the available i -band fluxes, r , u , IRAC/ ch 2, and z bands provide most of the information regarding the redshift with importance decreasing from r band to z band. We also find that for the same sample, IRAC/ ch 2, Y , r , and u bands are the most relevant bands in stellar-mass measurements with decreasing order of importance. Investigating the intercorrelation between the bands, we train a model to predict UVISTA observations in near-IR from H20-like observations. We find that magnitudes in the YJH bands can be simulated/predicted with an accuracy of 1 σ mag scatter ≲0.2 for galaxies brighter than 24 AB mag in near-IR bands. One should note that these conclusions depend on the selection criteria of the sample. For any new sample of galaxies with a different selection, these results should be remeasured. Our results suggest that in the presence of a limited number of bands, a machine-learning model trained over the population of observed galaxies with extensive spectral coverage outperforms template fitting. Such a machine-learning model maximally comprises the information acquired over available extensive surveys and breaks degeneracies in the parameter space of template fitting inevitable in the presence of a few bands.
    Type of Medium: Online Resource
    ISSN: 0004-637X , 1538-4357
    RVK:
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2023
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 1473835-1
    SSG: 16,12
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  • 9
    In: The Astrophysical Journal, American Astronomical Society, Vol. 951, No. 2 ( 2023-07-01), p. 147-
    Abstract: High-resolution imaging of galaxies in rest-frame UV has revealed the existence of giant star-forming clumps prevalent in high-redshift galaxies. Studying these substructures provides important information about their formation and evolution and informs theoretical galaxy evolution models. We present a new method to identify clumps in galaxies’ high-resolution rest-frame UV images. Using imaging data from CANDELS and UVCANDELS, we identify star-forming clumps in an HST/F160W ≤ 25 AB mag sample of 6767 galaxies at 0.5 ≤ z ≤ 3 in four fields, GOODS-N, GOODS-S, EGS, and COSMOS. We use a low-passband filter in Fourier space to reconstruct the background image of a galaxy and detect small-scale features (clumps) on the background-subtracted image. Clumpy galaxies are defined as those having at least one off-center clump that contributes a minimum of 10% of the galaxy’s total rest-frame UV flux. We measure the fraction of clumpy galaxies ( f clumpy ) as a function of stellar mass, redshift, and galaxy environment. Our results indicate that f clumpy increases with redshift, reaching ∼65% at z ∼ 1.5. We also find that f clumpy in low-mass galaxies ( 9.5 ≤ log ( M * / M ⊙ ) ≤ 10 ) is 10% higher compared to that of their high-mass counterparts ( log ( M * / M ⊙ ) 〉 10.5 ). Moreover, we find no evidence of significant environmental dependence of f clumpy for galaxies at the redshift range of this study. Our results suggest that the fragmentation of gas clouds under violent disk instability remains the primary driving mechanism for clump formation, and incidents common in dense environments, such as mergers, are not the dominant processes.
    Type of Medium: Online Resource
    ISSN: 0004-637X , 1538-4357
    RVK:
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2023
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 1473835-1
    SSG: 16,12
    Library Location Call Number Volume/Issue/Year Availability
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  • 10
    In: The Astrophysical Journal, American Astronomical Society, Vol. 952, No. 2 ( 2023-08-01), p. 110-
    Abstract: We present the Texas Euclid Survey for Ly α (TESLA), a spectroscopic survey in the 10 deg 2 of the Euclid North Ecliptic Pole (NEP) field. Using TESLA, we study how the physical properties of Ly α emitters (LAEs) correlate with Ly α emission to understand the escape of Ly α emission from galaxies at redshifts of 2–3.5. We present an analysis of 43 LAEs performed in the NEP field using early data from the TESLA survey. We use Subaru Hyper Suprime-Cam imaging in the grizy bands, Spitzer/IRAC channels 1 and 2 from the Hawaii 20 deg 2 (H20) survey, and spectra acquired by the Visible Integral-Field Replicable Unit Spectrograph (VIRUS) on the Hobby–Eberly Telescope. We perform spectral energy distribution (SED) fitting to compute the galaxy properties of 43 LAEs, and study correlations between stellar mass, star formation rate (SFR), and dust to the Ly α rest-frame equivalent width ( W Ly α ). We uncover marginal (1 σ significance) correlations between stellar mass and W Ly α , and SFR and W Ly α , with a Spearman correlation coefficient of −0. 34 − .14 + .17 and −0. 37 − .14 + .16 , respectively. We show that the W Ly α distribution of the 43 LAEs is consistent with being drawn from an exponential distribution with an e-folding scale of W 0 = 150 Å. Once complete the TESLA survey will enable the study of ≳50,000 LAEs to explore more correlations between galaxy properties and W Ly α . The large sample size will allow the construction of a predictive model for W Ly α as a function of SED-derived galaxy properties, which could be used to improve Ly α -based constraints on reionization.
    Type of Medium: Online Resource
    ISSN: 0004-637X , 1538-4357
    RVK:
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2023
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 1473835-1
    SSG: 16,12
    Library Location Call Number Volume/Issue/Year Availability
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