We present results from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CAN-DELS) photometric redshift methods investigation. In this investigation, the results from eleven participants, each using a different combination of photometric redshift code, template spectral energy distributions (SEDs) and priors, are used to examine the properties of photometric redshifts applied to deep fields with broad-band multi-wavelength coverage. The photometry used includes U -band through mid-infrared filters and was derived using the TFIT method. Comparing the results, we find that there is no particular code or set of template SEDs that results in significantly better photometric redshifts compared to others. However, we find codes producing the lowest scatter and outlier fraction utilize a training sample to optimize photometric redshifts by adding zero-point offsets, template adjusting or adding extra smoothing errors. These results therefore stress the importance of the training procedure. We find a strong dependence of the photometric redshift accuracy on the signal-to-noise ratio of the photometry. On the other hand, we find a weak dependence of the photometric redshift scatter with redshift and galaxy color. We find that most photometric redshift codes quote redshift errors (e.g., 68% confidence intervals) that are too small compared to that expected from the spectroscopic control sample. We find that all codes show a statistically significant bias in the photometric redshifts. However, the bias is in all cases smaller than the scatter, the latter therefore dominates the errors. Finally, we find that combining results from multiple codes significantly decreases the photometric redshift scatter and outlier fraction. We discuss different ways of combining data to produce accurate photometric redshifts and error estimates. 1 2 Dahlen et al.

This is the second paper in a series aimed at investigating the main sources of uncertainty in measuring the observable parameters in galaxies from their Spectral Energy Distributions (SEDs). In the first paper we presented a detailed account of the photometric redshift measurements and an error analysis of this process. In this paper we perform a comprehensive study of the main sources of random and systematic error in stellar mass estimates for galaxies, and their relative contributions to the associated error budget. Since there is no prior knowledge of the stellar mass of galaxies (unlike their photometric redshifts), we use mock galaxy catalogs with simulated multiwaveband photometry and known redshift, stellar mass, age and extinction for individual galaxies. The multi-waveband photometry for the simulated galaxies were generated in 13 filters spanning from U-band to mid-infrared wavelengths. Given different parameters affecting stellar mass measurement (photometric S/N ratios, SED fitting errors and systematic effects), the inherent degeneracies and correlated errors, we formulated different simulated galaxy catalogs to quantify these effects individually. For comparison, we also generated catalogs based on observed photometric data of real galaxies in the GOODS-South field, spanning the same passbands. The simulated and observed catalogs were provided to a number of teams within the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) collaboration to estimate the stellar masses for individual galaxies. A total of eleven teams participated, with different combinations of stellar mass measurement codes/methods, population synthesis models, star formation histories, extinction and age. For each simulated galaxy, the differences between the input stellar masses, M input , and those estimated by each team, M est , is defined as ∆ log(M ) ≡ log(M estimated ) − log(M input ), and used to identify the most fundamental parameters affecting stellar mass estimate in galaxies, with the following results: (1). no significant bias in ∆log(M ) was found among different codes, with all having comparable scatter (σ(∆log(M )) = 0.136 dex). The estimated stellar mass values are seriously affected by low photometric S/N ratios, with the rms scatter increasing for galaxies with H AB > 26 mag.; (2). A source of error contributing to the scatter in ∆log(M ) is found to be due to photometric uncertainties (0.136 dex) and low resolution in age and extinction grids when generating the SED templates;(3). The median of stellar masses among different methods provides a stable measure of the mass associated with any given galaxy (σ(∆log(M )) = 0.142 dex); (4). The ∆log(M ) values are strongly correlate with deviations in age (defined as the difference between the estimated and expected values), with a weaker correlation with extinction; (5). the rms scatter in the estimated stellar masses due to free parameters (after fixing redshifts and IMF) are quantified and found to be σ(∆log(M )) = 0.110 dex; (6). Using the...

We report the results of the counterpart identification and a detailed analysis of the physical properties of the 48 sources discovered in our deep 1.1‐mm wavelength imaging survey of the Great Observatories Origins Deep Survey‐South (GOODS‐S) field using the AzTEC instrument on the Atacama Submillimeter Telescope Experiment. One or more robust or tentative counterpart candidate is found for 27 and 14 AzTEC sources, respectively, by employing deep radio continuum, Spitzer/Multiband Imaging Photometer for Spitzer and Infrared Array Camera, and Large APEX Bolometer Camera 870 μm data. Five of the sources (10 per cent) have two robust counterparts each, supporting the idea that these galaxies are strongly clustered and/or heavily confused. Photometric redshifts and star formation rates (SFRs) are derived by analysing ultraviolet(UV)‐to‐optical and infrared(IR)‐to‐radio spectral energy distributions (SEDs). The median redshift of zmed∼ 2.6 is similar to other earlier estimates, but we show that 80 per cent of the AzTEC–GOODS sources are at z≥ 2, with a significant high‐redshift tail (20 per cent at z≥ 3.3). Rest‐frame UV and optical properties of AzTEC sources are extremely diverse, spanning 10 mag in the i‐ and K‐band photometry (a factor of 104 in flux density) with median values of i= 25.3 and K= 22.6 and a broad range of red colour (i−K= 0–6) with an average value of i−K≈ 3. These AzTEC sources are some of the most luminous galaxies in the rest‐frame optical bands at z≥ 2, with inferred stellar masses M*= (1–30) × 1010 M⊙ and UV‐derived SFRs of SFRUV≳ 101‐3 M⊙ yr−1. The IR‐derived SFR, 200–2000 M⊙ yr−1, is independent of z or M*. The resulting specific star formation rates, SSFR ≈ 1–100 Gyr−1, are 10–100 times higher than similar mass galaxies at z= 0, and they extend the previously observed rapid rise in the SSFR with redshift to z= 2–5. These galaxies have a SFR high enough to have built up their entire stellar mass within their Hubble time. We find only marginal evidence for an active galactic nucleus (AGN) contribution to the near‐IR and mid‐IR SEDs, even among the X‐ray detected sources, and the derived M* and SFR show little dependence on the presence of an X‐ray bright AGN.

This is the first in a series of papers examining the demographics of star-forming galaxies at 0.2 < z < 2.5 in CANDELS. We study 9,100 galaxies from GOODS-S and UDS having published values of redshifts, masses, star-Corresponding author: Jerome Fang jjfang@ucolick.org arXiv:1710.05489v2 [astro-ph.GA] 6 Apr 2018 2 FANG ET AL.formation rates (SFRs), and dust attenuation (A V ) derived from UV-optical SED fitting. In agreement with previous works, we find that the U V J colors of a galaxy are closely correlated with its specific star-formation rate (SSFR) and A V . We define rotated U V J coordinate axes, termed S SED and C SED , that are parallel and perpendicular to the starforming sequence and derive a quantitative calibration that predicts SSFR from C SED with an accuracy of ∼ 0.2 dex. SFRs from UV-optical fitting and from UV+IR values based on Spitzer /MIPS 24 µm agree well overall, but systematic differences of order 0.2 dex exist at high and low redshifts. A novel plotting scheme conveys the evolution of multiple galaxy properties simultaneously, and dust growth, as well as star-formation decline and quenching, exhibit "massaccelerated evolution" ("downsizing"). A population of transition galaxies below the star-forming main sequence is identified. These objects are located between star-forming and quiescent galaxies in U V J space and have lower A V and smaller radii than galaxies on the main sequence. Their properties are consistent with their being in transit between the two regions. The relative numbers of quenched, transition, and star-forming galaxies are given as a function of mass and redshift.

We present a catalogue of 17 filamentary X-ray features located within a 68\times34 arcmin^2 view centred on the Galactic Centre region from images taken by Chandra. These features are described by their morphological and spectral properties. Many of the X-ray features have non-thermal spectra that are well fitted by an absorbed power law. Of the 17 features, we find six that have not been previously detected, four of which are outside the immediate 20\times20 arcmin^2 area centred on the Galactic Centre. Seven of the 17 identified filaments have morphological and spectral properties expected for pulsar wind nebulae (PWNe) with X-ray luminosities of 5\times10^32 to 10^34 erg s^-1 in the 2.0-10.0 keV band and photon indices in the range of \Gamma = 1.1 to 1.9. In one feature, we suggest the strong neutral Fe K\alpha emission line to be a possible indicator for past activity of Sgr A*. For G359.942-0.03, a particular filament of interest, we propose the model of a ram pressure confined stellar wind bubble from a massive star to account for the morphology, spectral shape and 6.7 keV He-like Fe emission detected. We also present a piecewise spectral analysis on two features of interest, G0.13-0.11 and G359.89-0.08, to further examine their physical interpretations. This analysis favours the PWN scenario for these features.Comment: 12 pages, 10 figure