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Intensity mapping provides a unique means to probe the epoch of reionization (EoR), when the neutral intergalactic medium was ionized by the energetic photons emitted from the first galaxies. The [CII] 158$��$m fine-structure line is typically one of the brightest emission lines of star-forming galaxies and thus a promising tracer of the global EoR star-formation activity. However, [CII] intensity maps at $6 \lesssim z \lesssim 8$ are contaminated by interloping CO rotational line emission ($3 \leq J_{\rm upp} \leq 6$) from lower-redshift galaxies. Here we present a strategy to remove the foreground contamination in upcoming [CII] intensity mapping experiments, guided by a model of CO emission from foreground galaxies. The model is based on empirical measurements of the mean and scatter of the total infrared luminosities of galaxies at $z < 3$ and with stellar masses $M_{*} > 10^{8}\,\rm M_{\rm \odot}$ selected in $K$-band from the COSMOS/UltraVISTA survey, which can be converted to CO line strengths. For a mock field of the Tomographic Ionized-carbon Mapping Experiment (TIME), we find that masking out the "voxels" (spectral-spatial elements) containing foreground galaxies identified using an optimized CO flux threshold results in a $z$-dependent criterion $m^{\rm AB}_{\rm K} \lesssim 22$ (or $M_{*} \gtrsim 10^{9} \,\rm M_{\rm \odot}$) at $z < 1$ and makes a [CII]/CO$_{\rm tot}$ power ratio of $\gtrsim 10$ at $k=0.1$ $h$/Mpc achievable, at the cost of a moderate $\lesssim 8\%$ loss of total survey volume., 14 figures, 4 tables, re-submitted to ApJ after addressing reviewer's comments. Comments welcome

Spectral distortions in the cosmic microwave background over the 40--200~MHz band are imprinted by neutral hydrogen in the intergalactic medium prior to the end of reionization. This signal, produced in the redshift range $z = 6-34$ at the rest frame wavelength of 21 cm, has not been detected yet; and poor understanding of high redshift astrophysics results in a large uncertainty in the expected spectrum. The SARAS~2 radiometer was purposely designed to detect the sky-averaged 21-cm signal. The instrument, deployed at the Timbaktu Collective (Southern India) in April--June 2017, collected 63~hr of science data, which were examined for the presence of the cosmological 21-cm signal. In our previous work the first-light data from SARAS~2 radiometer were analyzed with Bayesian likelihood-ratio tests using $264$ plausible astrophysical scenarios. In this paper we re-examine the data using an improved analysis based on the frequentist approach and forward modeling. We show that SARAS~2 data rejects 27 models, out of which 25 are rejected at a significance $>5\sigma$. All the rejected models share the scenario of inefficient heating of the primordial gas by the first population of X-ray sources along with rapid reionization., Comment: 7 pages, 3 figures, 1 table; submitted to ApJ. Comments and suggestions are welcome

arXiv:1710.00826v1, We analyze the properties of a multiply imaged Lyα (Lyα) emitter at z = 5.75 identified through SHARDS Frontier Fields intermediate-band imaging of the Hubble Frontier Fields (HFF) cluster Abell 370. The source, A370-L57, has low intrinsic luminosity (M ∼ -16.5), steep UV spectral index (β = -2.4 ± 0.1), and extreme rest-frame equivalent width of Lyα. Two different gravitational lens models predict high magnification (μ ∼ 10-16) for the two detected counterimages, separated by 7″, while a predicted third counterimage (μ ∼ 3-4) is undetected. We find differences of ∼50% in magnification between the two lens models, quantifying our current systematic uncertainties. Integral field spectroscopy of A370-L57 with MUSE shows a narrow (FWHM = 204 ± 10 km s) and asymmetric Lyα profile with an integrated luminosity L(Lyα) ∼ 10 erg s. The morphology in the Hubble Space Telescope bands comprises a compact clump (r < 100 pc) that dominates the Lyα and continuum emission and several fainter clumps at projected distances ≲1 kpc that coincide with an extension of the Lyα emission in the SHARDS F823W17 and MUSE observations. The latter could be part of the same galaxy or an interacting companion. We find no evidence of a contribution from active galactic nuclei to the Lyα emission. Fitting of the spectral energy distribution with stellar population models favors a very young (t < 10 Myr), low-mass (), and metal-poor (Z ≲ 4 10) stellar population. Its modest star formation rate (SFR ∼ 1.0 yr) implies high specific SFR (sSFR ∼ 2.5 10 yr) and SFR density ( yr kpc). The properties of A370-L57 make it a good representative of the population of galaxies responsible for cosmic reionization., A.H.-C. and P.G.P.-G. acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) under grants AYA2012-31277, AYA2015-70815-ERC, and AYA2015-63650-P. J.M.D. acknowledges support of the projects AYA2015-64508-P (MINECO/FEDER, UE), AYA2012-39475-C02-01, and the consolider project CSD2010-00064 funded by MINECO. D.J.L. and J.R. acknowledge support from the ERC starting grant 336736-CALENDS. R.A.M. acknowledges support by the Swiss National Science Foundation. A.A.-H. acknowledges funding by the MINECO grant AYA2015-64346-C2-1-P, which is partly funded by the FEDER program. H.D.S. acknowledges funding from the program ANR-T-ERC ASTROBRAIN. P.S. acknowledges funding from the Swiss National Science Foundation under grant P2GEP2_165426. J.M.R.E. acknowledges funding by the MINECO grant AYA2015-70498-C2-1-R. H.D. acknowledges financial support from the Spanish 2014 Ramón y Cajal program MINECO RYC-2014-15686.

著者人数: 15名, Accepted: 2017-03-19, 資料番号: SA1170033000

We provide an holistic view of galaxy evolution at high redshift z>4, that incorporates the constraints from various astrophysical/cosmological probes, including the estimate of the cosmic SFR density from UV/IR surveys and long GRB rates, the cosmic reionization history after the latest Planck measurements, and the missing satellites issue. We achieve this goal in a model-independent way by exploiting the SFR functions derived by Mancuso et al. (2016) on the basis of an educated extrapolation of the latest UV/far-IR data from HST/Herschel, and already tested against a number of independent observables. Our SFR functions integrated down to an UV magnitude limit M_UV, Comment: 13 pages, 5 figures, 1 table. Accepted by ApJ

We present the analysis of deep HST multi-band imaging of the BDF field specifically designed to identify faint companions around two of the few Ly-alpha emitting galaxies spectroscopically confirmed at z~7 (Vanzella et al. 2011). Although separated by only 4.4 proper Mpc these galaxies cannot generate HII regions large enough to explain visibility of their Ly-alpha line, thus requiring a population of fainter ionizing sources in their vicinity. We use deep HST and VLT-Hawk-I data to select z~7 Lyman break galaxies around the emitters. We select 6 new robust z~7 LBGs at Y~26.5-27.5 whose average spectral energy distribution is consistent with the objects being at the redshift of the close-by Ly-alpha emitters. The resulting number density of z~7 LBGs in the BDF field is a factor ~3-4 higher than expected in random pointings of the same size. We compare these findings with cosmological hydrodynamic plus radiative transfer simulations of a universe with a half neutral IGM: we find that indeed Ly-alpha emitter pairs are only found in completely ionized regions characterized by significant LBG overdensities. Our findings match the theoretical prediction that the first ionization fronts are generated within significant galaxy overdensities and support a scenario where faint, "normal" star-forming galaxies are responsible for reionization., Comment: Accepted for publication in The Astrophysical Journal Letters. 6 pages, 5 figures