Dust properties of Lyman-break galaxies atz~ 3

Abstract

Context. Since the mid-1990s, the sample of Lyman break galaxies (LBGs) has been growing thanks to the increasing sensitivities in the optical and in near-infrared telescopes for objects at z > 2.5. However, the dust properties of the LBGs are poorly known because the samples are small and/or biased against far-infrared or sub-mm observations. Aims. This work explores from a statistical point of view the far-infrared (far-IR) and sub-millimeter (sub-mm) properties of a large sample of LBGs at z ∼ 3 that cannot be individually detected from current far-infrared observations. Methods. We select a sample of 22, 000 LBGs at 2.5 < z < 3.5 in the COSMOS field using the dropout technique. The large number of galaxies included in the sample allows us to split it in several bins as a function of UV luminosity (L FUV ), UV continuum slope (β UV ) and stellar mass (M * ) to better sample their variety. We stack in PACS (100 and 160 µm) images from PACS Evolution Probe survey (PEP), SPIRE (250, 350 and 500µm) images from the Herschel Multi-tied Extragalactic Survey (HerMES) programs and AzTEC (1.1 mm) images from the Atacama Submillimetre Telescope Experiment (ASTE). Our stacking procedure corrects the biases induced by galaxy clustering and incompleteness of our input catalogue in dense regions. Results. We obtain the full infrared spectral energy distributions (SED) of subsamples of LBGs and derive the mean IR luminosity as a function of L FUV , β UV and M * . The average IRX (or dust attenuation) is roughly constant over the L FUV range, with a mean of 7.9 (1.8 mag). However, it is correlated with β UV , A FUV = (3.15 ± 0.12) + (1.47 ± 0.14) β UV , and stellar mass, log (IRX) = (0.84 ± 0.11) log M * /10 10.35 + 1.17 ± 0.05. We investigate using a statistically-controlled stacking analysis as a function of (M * , β UV ) the dispersion of the IRX-β UV and IRX-M * plane. On the one hand, the dust attenuation shows a departure by up to 2.8 mag above the mean IRX-β UV relation, when log(M * [M ]) increases from 9.75 to 11.5 in the same β UV bin. That strongly suggests that M * plays an important role in shaping the IRX-β UV plane. On the other hand, the IRX-M * plane is less dispersed for variation in the β UV . However, the dust attenuation shows a departure by up to 1.3 mag above the mean IRX-M * relation, when β UV increases from -1.7 to 0.5 in the same M * bin. The low stellar mass LBGs (log(M * [M ]) < 10.5) and red β UV (β UV > −0.7), 15% of the total sample, present a large dust attenuation than the mean IRX-M * , but they still are in agreement with the mean IRX-β UV relation. We suggest that we have to combine both, IRX-β UV and IRX-M * , relations to obtain the best estimation of the dust attenuation from the UV and NIR properties of the galaxies (L FUV , β UV , M * ). Our results enable us to study the average relation between star-formation rate (SFR) and stellar mass, and we show that our LBG sample lies on the main sequence of star formation at z ∼ 3. we demonstrate that the SFR is underestimate for LBGs with hig...

INFERRED Hα FLUX AS A STAR FORMATION RATE INDICATOR AT z ∼ 4–5: IMPLICATIONS FOR DUST PROPERTIES, BURSTINESS, AND THE z = 4–8 STAR FORMATION RATE FUNCTIONS

“…Current observational constraints on the IR-to-UV luminosity ratio as a function of the UV continuum slope (β) using stacks of UV-selected galaxies (left panel) and constraints on individual galaxies from ALMA and PdBI (right panel). While the stacking results by Coppin et al (2015) over the redshift rangez 35 -are in good agreement with the dust calibration needed to bring Hα-and UV-based SFR measurements, i.e., b =+ A 1.99 2.5 1600 () (see Section 5.1), many of the results suggest lower dust corrections (Cooray et al 2014;Capak et al 2015;Schaerer et al 2015;Watson et al 2015;Álvarez-Márquez et al 2016;Bouwens et al 2016a). At present, the impact that dust has on the observed UV brightness and SFRs of z∼4-5 galaxies is not clear, on the basis of far-IR observations.…”

The Galaxy–Halo Connection in High-redshift Universe: Details and Evolution of Stellar-to-halo Mass Ratios of Lyman Break Galaxies on CFHTLS Deep Fields

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The Strong Gravitationally Lensed Herschel Galaxy HLock01: Optical Spectroscopy Reveals a Close Galaxy Merger with Evidence of Inflowing Gas

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