Dust Attenuation in High Redshift Galaxies: “Diamonds in the Sky”

Scoville, N. Z.; Faisst, Andreas L.; Capak, P.; Kakazu, Y.; Li, Gongjie; Steinhardt, Charles L.

doi:10.1088/0004-637x/800/2/108

Cited by 87 publications

(123 citation statements)

References 23 publications

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“…Such simple forms for τ λ with a logarithmic slope of −1.3 are expected from various detailed measurements of the dust extinction curves in the Milky Way galaxy (Seaton 1979), the Large Magellanic Cloud (Fitzpatrick 1986), local starburst galaxies (Calzetti et al 2000), and even normal star-forming galaxies at z=2-4 (Scoville et al 2015). For the birth clouds, a similar optical depth is assumed with…”

Section: Analytical Models To Explain Irx−βin Typical Local Tomentioning

confidence: 84%

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Are High-redshift Galaxies Hot? Temperature of z > 5 Galaxies and Implications for Their Dust Properties

Faisst

Capak

Yan

et al. 2017

ApJ

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126

163

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Recent studies have found a significant evolution and scatter in the relationship between the UV spectral slope (β UV ) and the infrared excess (IRX; L IR /L UV ) at z>4, suggesting different dust properties of these galaxies. The total farinfrared (FIR) luminosity is key for this analysis, but it is poorly constrained in normal (main-sequence) star-forming z>5 galaxies, where often only one single FIR point is available. To better inform estimates of the FIR luminosity, we construct a sample of local galaxies and three low-redshift analogues of z>5 systems. The trends in this sample suggest that normal high-redshift galaxies have a warmer infrared (IR) spectral energy distribution (SED) compared to average z<4 galaxies that are used as priors in these studies. The blueshifted peak and mid-IR excess emission could be explained by a combination of a larger fraction of metal-poor interstellar medium being optically thin to ultraviolet (UV) light and a stronger UV radiation field due to high star formation densities. Assuming a maximally warm IR SED suggests a 0.6 dex increase in total FIR luminosities, which removes some tension between the dust attenuation models and observations of the IRX−βrelation at z>5. Despite this, some galaxies still fall below the minimum IRX −βrelation derived with standard dust cloud models. We propose that radiation pressure in these highly star-forming galaxies causes a spatial offset between dust clouds and young star-forming regions within the lifetime of O/B stars. These offsets change the radiation balance and create viewing-angle effects that can change UV colors at fixed IRX. We provide a modified model that can explain the location of these galaxies on the IRX−βdiagram.

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Section: Analytical Models To Explain Irx−βin Typical Local Tomentioning

confidence: 84%

“…Furthermore, the UV slope β also depends on other galaxy properties such as star formation history (SFH), age of the stellar population, and metallicity. However, in comparison to dust, these effects are shown to contribute little to β in the case of young galaxies in the early universe (Bouwens et al 2012;Scoville et al 2015).…”

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confidence: 99%

Are High-redshift Galaxies Hot? Temperature of z > 5 Galaxies and Implications for Their Dust Properties

Faisst

Capak

Yan

et al. 2017

ApJ

Self Cite

126

163

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“…The MW curve exhibits the 2175 Å bump that could explain the flux decrease in the z 850 band, while uncertainties are too large to discriminate between a curve with or without the 2175 Å bump. However, Scoville et al (2015) report that their data are consistent with the presence of the 2175 Å bump, while for Reddy et al (2015) this presence is only marginal. We derive the β slope from the UV spectrum, using the wavelength windows described in Calzetti et al (1994), but excluding the 10th window because it is outside the UV spectrum wavelength coverage.…”

Section: Appendix A: Emission Lines Dust Correctionmentioning

confidence: 95%

An extreme [O III] emitter atz= 3.2: a low metallicity Lyman continuum source

Barros

Vanzella

Amorín

et al. 2015

A&A

185

158

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Aims. Cosmic reionization is an important process occurring in the early epochs of the Universe. However, because of observational limitations due to the opacity of the intergalactic medium to Lyman continuum photons, the nature of ionizing sources is still not well constrained. While high-redshift star-forming galaxies are thought to be the main contributors to the ionizing background at z > 6, it is impossible to directly detect their ionizing emission. Therefore, looking at intermediate redshift analogues (z ∼ 2−4) can provide useful hints about cosmic reionization. Methods. We investigate the physical properties of one of the best Lyman continuum emitter candidate at z = 3.212 found in the GOODS-S/CANDELS field with photometric coverage from the U to the MIPS 24 μm band and VIMOS/VLT and MOSFIRE/Keck spectroscopy. These observations allow us to derive physical properties such as stellar mass, star formation rate, age of the stellar population, dust attenuation, metallicity, and ionization parameter, and to determine how these parameters are related to the Lyman continuum emission. Results. Investigation of the UV spectrum confirms a direct spectroscopic detection of the Lyman continuum emission with S /N > 5.Non-zero Lyα flux at the systemic redshift and high Lyman-α escape fraction ( f esc (Lyα) ≥ 0.78) suggest a low H i column density.The weak C and Si low-ionization absorption lines are also consistent with a low covering fraction along the line of sight. The subsolar abundances are consistent with a young and extreme starburst. The [O iii]λλ4959, 5007+Hβ equivalent width (EW) is one of the largest reported for a galaxy at z > 3 (EW([O iii]λλ4959, 5007 + Hβ) 1600 Å, rest-frame; 6700 Å observed-frame) and the near-infrared spectrum shows that this is mainly due to an extremely strong [O (>10) and high ionization parameter are consistent with prediction from photoionization models in the case of a density-bounded nebula scenario. Furthermore, the EW([O iii]λλ4959, 5007+Hβ) is comparable to recent measurements reported at z ∼ 7−9, in the reionization epoch. We also investigate the possibility of an AGN contribution to explain the ionizing emission but most of the AGN identification diagnostics suggest that stellar emission dominates instead. Conclusions. This source is currently the first high-z example of a Lyman continuum emitter exhibiting indirect and direct evidences of a Lyman continuum leakage and having physical properties consistent with theoretical expectation from Lyman continuum emission from a density-bounded nebula. A low H i column density, low covering fraction, compact star formation activity, and a possible interaction/merging of two systems may contribute to the Lyman continuum photon leakage.

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“…Dust extinction is implemented assuming 0 E(B − V) 0.8. We allow for only one attenuation law, that is, Calzetti et al (2000) with the addition of the 2175 Å feature (see Scoville et al 2015).…”

Section: Galaxy Stellar Massmentioning

confidence: 99%

The COSMOS2015 galaxy stellar mass function

Davidzon

Ilbert

Laigle

et al. 2017

A&A

408

613

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We measure the stellar mass function (SMF) and stellar mass density of galaxies in the COSMOS field up to z ∼ 6. We select them in the near-IR bands of the COSMOS2015 catalogue, which includes ultra-deep photometry from UltraVISTA-DR2, SPLASH, and Subaru/Hyper SuprimeCam. At z > 2.5 we use new precise photometric redshifts with error σ z = 0.03(1 + z) and an outlier fraction of 12%, estimated by means of the unique spectroscopic sample of COSMOS (∼100 000 spectroscopic measurements in total, more than one thousand having robust z spec > 2.5). The increased exposure time in the DR2, along with our panchromatic detection strategy, allow us to improve the completeness at high z with respect to previous UltraVISTA catalogues (e.g. our sample is >75% complete at 10 10 M and z = 5). We also identify passive galaxies through a robust colour-colour selection, extending their SMF estimate up to z = 4. Our work provides a comprehensive view of galaxy-stellar-mass assembly between z = 0.1 and 6, for the first time using consistent estimates across the entire redshift range. We fit these measurements with a Schechter function, correcting for Eddington bias. We compare the SMF fit with the halo mass function predicted from ΛCDM simulations, finding that at z > 3 both functions decline with a similar slope in the high-mass end. This feature could be explained assuming that mechanisms quenching star formation in massive haloes become less effective at high redshifts; however further work needs to be done to confirm this scenario. Concerning the SMF low-mass end, it shows a progressive steepening as it moves towards higher redshifts, with α decreasing from −1.47 +0.02 −0.02 at z 0.1 to −2.11 +0.30 −0.13 at z 5. This slope depends on the characterisation of the observational uncertainties, which is crucial to properly remove the Eddington bias. We show that there is currently no consensus on the method to quantify such errors: different error models result in different best-fit Schechter parameters.

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Dust Attenuation in High Redshift Galaxies: “Diamonds in the Sky”

Cited by 87 publications

References 23 publications

Are High-redshift Galaxies Hot? Temperature of z > 5 Galaxies and Implications for Their Dust Properties

Are High-redshift Galaxies Hot? Temperature of z > 5 Galaxies and Implications for Their Dust Properties

An extreme [O III] emitter atz= 3.2: a low metallicity Lyman continuum source

The COSMOS2015 galaxy stellar mass function

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