We report on the detailed analysis of a gravitationally lensed Y-band dropout, A2744_YD4, selected from deep Hubble Space Telescope imaging in the Frontier Field cluster Abell 2744. Band 7 ...observations with the Atacama Large Millimeter/submillimeter Array (ALMA) indicate the proximate detection of a significant 1 mm continuum flux suggesting the presence of dust for a star-forming galaxy with a photometric redshift of . Deep X-SHOOTER spectra confirms the high-redshift identity of A2744_YD4 via the detection of Ly emission at a redshift z = 8.38. The association with the ALMA detection is confirmed by the presence of O iii 88 m emission at the same redshift. Although both emission features are only significant at the 4 level, we argue their joint detection and the positional coincidence with a high-redshift dropout in the Hubble Space Telescope images confirms the physical association. Analysis of the available photometric data and the modest gravitational magnification ( ) indicates A2744_YD4 has a stellar mass of ∼2 × 109 , a star formation rate of ∼20 yr−1 and a dust mass of ∼6 × 106 . We discuss the implications of the formation of such a dust mass only after the onset of cosmic reionization.
The extended Baryon Oscillation Spectroscopic Survey of the Sloan Digital Sky Survey (SDSS-IV/eBOSS) has an extensive quasar program that combines several selection methods. Among these, the ...photometric variability technique provides highly uniform samples, which are unaffected by the redshift bias of traditional optical-color selections, when z = 2.7−3.5 quasars cross the stellar locus or when host galaxy light affects quasar colors at z< 0.9. We present the variability selection of quasars in eBOSS, focusing on a specific program that led to a sample of 13 876 quasars to gdered = 22.5 over a 94.5 deg2 region in Stripe 82, which has an areal density 1.5 times higher than over the rest of the eBOSS footprint. We use these variability-selected data to provide a new measurement of the quasar luminosity function (QLF) in the redshift range of 0.68 <z< 4.0. Our sample is denser and reaches more deeply than those used in previous studies of the QLF, and it is among the largest ones. At the faint end, our QLF extends to Mg(z = 2) = −21.80 at low redshift and to Mg(z = 2) = −26.20 at z ~ 4. We fit the QLF using two independent double-power-law models with ten free parameters each. The first model is a pure luminosity-function evolution (PLE) with bright-end and faint-end slopes allowed to be different on either side of z = 2.2. The other is a simple PLE at z< 2.2, combined with a model that comprises both luminosity and density evolution (LEDE) at z> 2.2. Both models are constrained to be continuous at z = 2.2. They present a flattening of the bright-end slope at high redshift. The LEDE model indicates a reduction of the break density with increasing redshift, but the evolution of the break magnitude depends on the parameterization. The models are in excellent accord, predicting quasar counts that agree within 0.3% (resp., 1.1%) to g< 22.5 (resp., g< 23). The models are also in good agreement over the entire redshift range with models from previous studies.
Abstract
The inner kiloparsec regions surrounding sub-Eddington (luminosity less than 10
−3
in Eddington units,
L
Edd
) supermassive black holes (BHs) often show a characteristic network of dust ...filaments that terminate in a nuclear spiral in the central parsecs. Here we study the role and fate of these filaments in one of the least accreting BHs known, M31 (10
−7
L
Edd
) using hydrodynamical simulations. The evolution of a streamer of gas particles moving under the barred potential of M31 is followed from kiloparsec distance to the central parsecs. After an exploratory study of initial conditions, a compelling fit to the observed dust/ionized gas morphologies and line-of-sight velocities in the inner hundreds of parsecs is produced. After several million years of streamer evolution, during which friction, thermal dissipation, and self-collisions have taken place, the gas settles into a disk tens of parsecs wide. This is fed by numerous filaments that arise from an outer circumnuclear ring and spiral toward the center. The final configuration is tightly constrained by a critical input mass in the streamer of several 10
3
M
☉
(at an injection rate of 10
−4
M
⊙
yr
−
1
); values above or below this lead to filament fragmentation or dispersion respectively, which are not observed. The creation of a hot gas atmosphere in the region of ∼10
6
K is key to the development of a nuclear spiral during the simulation. The final inflow rate at 1 pc from the center is ∼1.7 × 10
−7
M
☉
yr
−1
, consistent with the quiescent state of the M31 BH.
ABSTRACT In this paper we present the results of our search for and study of z 6 galaxy candidates behind the third Frontier Fields (FFs) cluster, MACS J0717.5+3745, and its parallel field, combining ...data from Hubble and Spitzer. We select 39 candidates using the Lyman break technique, for which the clear non-detection in optical make the extreme mid-z interlopers hypothesis unlikely. We also take benefit from z 6 samples selected using the previous FF data sets of Abell 2744 and MACS 0416 to improve the constraints on the properties of very high redshift objects. We compute the redshift and the physical properties such emission lines properties, star formation rate, reddening, and stellar mass for all FF objects from their spectral energy distribution using templates including nebular emission lines. We study the relationship between several physical properties and confirm the trend already observed in previous surveys for evolution of star formation rate with galaxy mass and between the size and the UV luminosity of our candidates. The analysis of the evolution of the UV luminosity function with redshift seems more compatible with an evolution of density. Moreover, no robust z ≥ 8.5 object is selected behind the cluster field and few z ∼ 9 candidates have been selected in the two previous data sets from this legacy survey, suggesting a strong evolution in the number density of galaxies between z ∼ 8 and 9. Thanks to the use of the lensing cluster, we study the evolution of the star formation rate density produced by galaxies with L > 0.03 L , and confirm the strong decrease observed between z ∼ 8 and 9.
The second catalogue of Planck Sunyaev-Zeldovich (SZ) sources, hereafter PSZ2, represents the largest galaxy cluster sample selected by means of their SZ signature in a full-sky survey. Using ...telescopes at the Canary Island observatories, we conducted the long-term observational program 128- MULTIPLE-16/15B (hereafter LP15), a large and complete optical follow-up campaign of all the unidentified PSZ2 sources in the northern sky, with declinations above −15° and no correspondence in the first Planck catalogue PSZ1. This paper is the third and last in the series of LP15 results, after Streblyanska et al. (2019, A&A, 628, A13) and Aguado-Barahona et al. (2019, A&A, 631, A148), and presents all the spectroscopic observations of the full program. We complement these LP15 spectroscopic results with Sloan Digital Sky Survey archival data and other observations from a previous program (ITP13-08), and present a catalogue of 388 clusters and groups of galaxies including estimates of their velocity dispersion. The majority of them (356) are optical counterparts of PSZ2 sources. A subset of 297 of those clusters are used to construct the MSZ − Mdyn scaling relation based on the estimated SZ mass from Planck measurements and our dynamical mass estimates. We discuss and correct for different statistical and physical biases in the estimation of the masses, such as the Eddington bias when estimating MSZ and the aperture and the number of galaxies used to calculate Mdyn. The SZ-to-dynamical mass ratio for those 297 PSZ2 clusters is (1 − B) = 0.80 ± 0.04 (stat) ± 0.05 (sys), with only marginal evidence for a possible mass dependence for this factor. Our value is consistent with previous results in the literature, but is associated with a significantly smaller uncertainty due to the use of the largest sample size for this type of study.
We present a list of 13 candidate gravitationally lensed submillimeter galaxies (SMGs) from 95 deg super(2) of the Herschel Multi-tiered Extragalactic Survey, a surface density of 0.14 + or - 0.04 ...deg super(-2). The selected sources have 500 mum flux densities (S sub(500)) greater than 100 mJy. Gravitational lensing is confirmed by follow-up observations in 9 of the 13 systems (70%), and the lensing status of the four remaining sources is undetermined. We also present a supplementary sample of 29 (0.31 + or - 0.06 deg super(-2)) gravitationally lensed SMG candidates with S sub(500) = 80-100 mJy, which are expected to contain a higher fraction of interlopers than the primary candidates. The model predicts that 32%-74% of our S sub(500) > or =, slanted 100 mJy candidates are strongly gravitationally lensed (mu > or =, slanted 2), with the brightest sources being the most robust; this is consistent with the observational data. Thus, samples of strongly gravitationally lensed SMGs, such as those presented here, probe below the nominal Herschel detection limit at 500 mum.
Aims. We present in this letter the first analysis of a z ~ 8 galaxy candidate found in the Hubble and Spitzer imaging data of Abell 2744 as part of the Hubble Frontier Fields legacy program. ...Methods. We applied the most commonly used methods to select exceptionally high-redshift galaxies by combining non-detection and color criteria using seven HST bands. We used GALFIT on IRAC images to fit and subtract contamination of bright nearby sources.The physical properties were inferred from spectral energy distribution-fitting using templates with and without nebular emission. Results. This letter is focused on the brightest candidate we found (mF160W = 26.2) over the 4.9 arcmin2 field of view covered by the WFC3. It is not detected in the ACS bands and at 3.6 μm, while it is clearly detected at 4.5 μm with rather similar depths. This break in the IRAC data might be explained by strong OIII+Hβ lines at z ~ 8 that contribute to the 4.5 μm photometry. The best photo-z is found at z ~ 8.0+0.2-0.5, although solutions at low-redshift (z ~ 1.9) cannot be completely excluded , but they are strongly disfavored by the SED-fitting. The amplification factor is relatively small at μ = 1.49 ± 0.02. The star formation rate in this object ranges from 8 to 60 M⊙ yr-1, the stellar mass is on the order of M⋆ = (2.5−10) × 109 M⊙, and the size is r ≈ 0.35 ± 0.15 kpc. Conclusions. This object is one of the first z ~ 8 Lyman break galaxy candidates showing a clear break between 3.6 μm and 4.5 μm, which is consistent with the IRAC properties of the first spectroscopically confirmed galaxy at a similar redshift. Due to its brightness, the redshift of this object could potentially be confirmed by near-infrared spectroscopy with current 8−10 m telescopes. The nature of this candidate will be revealed in the coming months with the arrival of new ACS and Spitzer data, increasing the depth at optical and near-infrared wavelengths.
Abstract
Broad absorption lines (BALs) found in a significant fraction of quasar spectra identify high-velocity outflows that might be present in all quasars and could be a major factor in feedback ...to galaxy evolution. Understanding the nature of these flows requires further constraints on their physical properties, including their column densities, for which well-studied BALs, such as C iv λλ1548,1551, typically provide only a lower limit because of saturation effects. Low-abundance lines, such as P v λλ1118,1128, indicate large column densities, implying that outflows more powerful than measurements of C iv alone would indicate. We search through a sample of 2694 BAL quasars from the Sloan Digital Sky Survey III/Baryon Oscillation Spectroscopic Survey data release 9 quasar catalogue for such absorption, and we identify 81 ‘definite’ and 86 ‘probable’ detections of P v broad absorption, yielding a firm lower limit of 3.0–6.2 per cent for the incidence of such absorption among BAL quasars. The P v-detected quasars tend to have stronger C iv and Si iv absorption, as well as a higher incidence of LoBAL absorption, than the overall BAL quasar population. Many of the P v-detected quasars have C iv troughs that do not reach zero intensity (at velocities where P v is detected), confirming that the outflow gas only partially covers the UV continuum source. P v appears significantly in a composite spectrum of non-P v-detected BAL quasars, indicating that P v absorption (and large column densities) is much more common than indicated by our search results. Our sample of P v detections significantly increases the number of known P v detections, providing opportunities for follow-up studies to better understand BAL outflow energetics.
Context. The Hubble Space Telescope (HST) Frontier Fields (HFFs) project started at the end of 2013 with the aim of providing extremely deep images of six massive galaxy clusters. One of the main ...goals of this program is to push several telescopes to their limits to provide the best current view of the earliest stages of the Universe. The analysis of the initial data has already demonstrated the huge capabilities of the program. Aims. We present a detailed analysis of z ~ 8 objects behind the HFFs lensing cluster, MACSJ0416.1-2403, combining 0.3−1.6 μm imaging from HST, ground-based Ks imaging from VLT HAWK-I, and 3.6 μm and 4.5 μm Spitzer Space Telescope. The images probe to 5σ depths of ≈29 AB for HST, 25.6 AB for HAWK-I, and ≈0.310 and 0.391 μJy at 3.6 and 4.5 μm, respectively. With these datasets, we assess the photometric properties of z ~ 8 galaxies in this field, as well as their distribution in luminosity, to unprecedented sensitivity. Methods. We applied the classical Lyman break (LB) technique, which combines non detection criteria in bands blueward of the Lyman break at z ~ 8 and color-selection in bands redward of the break. To avoid contamination by mid-z interlopers, we required a strong break between optical and near-infrared data. We determined the photometric properties of z ~ 8 selected candidates using spectral energy distribution (SED)-fitting with standard library templates. The luminosity function at z ~ 8 is computed using a Monte-Carlo method taking advantage of the SED-fitting results. A piece of cautionary information is gleaned from new deep optical photometry of a previously identified z ~ 8 galaxy in this cluster, which is now firmly detected as a mid-z interloper with a strong ≈1.5 mag Balmer break (between F606W and F125W). Using the SED of this interloper, we estimated the contamination rate of our MACSJ0416.1−2403 sample, and that of previous samples in Abell 2744 that were based on HFF data, we highlight the dangers of pushing the LB technique too close to the photometry limits. Results. Our selection reliably recovers four objects with mF160W ranging from 26.0 to 27.9 AB that are located in modest-amplification regions (μ < 2.4). Two of the objects display a secondary break between the IRAC 3.6 μm and 4.5 μm bands, which could be associated to the Balmer break or emission lines at z ~ 8. The SED-fitting analysis suggests that all of these objects favor high-z solutions with no reliable secondary solutions. The candidates generally have star formation rates around ~10 M⊙/yr and sizes ranging from 0.2 to 0.5 kpc, which agrees well with previous observations and expectations for objects in the early Universe. The sample size and luminosity distribution are consistent with previous findings.
Aims. The Planck catalogues of Sunyaev –Zeldovich (SZ) sources, PSZ1 and PSZ2, are the largest catalogues of galaxy clusters selected through their SZ signature in the full sky. In 2013, we started a ...long-term observational programme at Canary Island observatories with the aim of validating ∼500 unconfirmed SZ sources. In this work we present results of the initial pre-screening of possible cluster counterparts using photometric and spectroscopic data of the Sloan Digital Sky Survey DR12. Our main aim is to identify previously unconfirmed PSZ2 cluster candidates and to contribute in the determination of the actual purity and completeness of Planck SZ source sample. Methods. Using the latest version of the PSZ2 catalogue, we selected all sources overlapping with the SDSS DR12 footprint and without redshift information. We validated these cluster fields following optical criteria (mainly distance with respect to the Planck pointing, magnitude of the brightest cluster galaxy, and cluster richness), and combined these criteria with the profiles of the Planck Compton y-maps. This combined procedure allows for a more robust identification of optical counterparts compared to simply cross-matching with existing SDSS cluster catalogues that have been constructed from earlier SDSS data releases. Results. The sample contains new redshifts for 37 Planck galaxy clusters that were not included in the original release of PSZ2 Planck catalogue. We detect three cases as possible multiple counterparts. We show that a combination of all available information (optical images and profile of SZ signal) can provide correct associations between the observed Planck SZ source and the optically identified cluster. We also show that Planck SZ detection is very sensitive even to high-z (z > 0.5) clusters. In addition, we also present updated spectroscopic information for 34 Planck PSZ1 sources (33 previously photometrically confirmed and 1 new identification).
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