The first estimate of radio jet proper motion at z &gt; 5

Abstract The extremely high-redshift (z = 5.3) radio source SDSS J102623.61+254259.5 (J1026+2542) is among the most distant and most luminous radio-loud active galactic nuclei (AGN) known to date. Its one-sided radio jet structure on milliarcsecond (mas) and ∼10-mas scales typical for blazars was first imaged at 5 GHz with very long baseline interferometry (VLBI) in 2006. Here we report on our dual-frequency (1.7 and 5 GHz) imaging observations performed with the European VLBI Network (EVN) in 2013. The prominent jet structure allows us to identify individual components whose apparent displacement can be detected over the time span of 7.33 yr. This is the first time when jet proper motions are directly derived in a blazar at z > 5. The small values of up to ∼0.1 mas yr−1 are consistent with what is expected in a relativistic cosmological model if redshift is a measure of distance. The apparent superluminal jet speeds, considered tentative because derived from two epochs only, exceed 10 c for three different components along the jet. Based on modelling its spectral energy distribution, J1026+2542 is known to have its X-ray jet oriented close to the line of sight, with significant Doppler boosting and a large bulk Lorentz factor (Γ ≈ 13). The new VLBI observations, indicating ∼2.3 × 1012 K lower limit to the core brightness temperature, are consistent with this picture. The spectral index in the core region is −0.35.

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Towards a census of high-redshift dusty galaxies with Herschel

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731888 ◽

2018 ◽

Vol 614 ◽

pp. A33 ◽

Cited By ~ 9

Author(s):

D. Donevski ◽

V. Buat ◽

F. Boone ◽

C. Pappalardo ◽

M. Bethermin ◽

...

Keyword(s):

Galaxy Evolution ◽

High Redshift ◽

Spectral Energy Distribution ◽

Formation Rate ◽

Far Infrared ◽

Virgo Cluster ◽

Spectral Energy ◽

Distribution Fitting ◽

Redshift Distribution ◽

Star Forming

Context. Over the last decade a large number of dusty star-forming galaxies has been discovered up to redshift z = 2 − 3 and recent studies have attempted to push the highly confused Herschel SPIRE surveys beyond that distance. To search for z ≥ 4 galaxies they often consider the sources with fluxes rising from 250 μm to 500 μm (so-called “500 μm-risers”). Herschel surveys offer a unique opportunity to efficiently select a large number of these rare objects, and thus gain insight into the prodigious star-forming activity that takes place in the very distant Universe. Aims. We aim to implement a novel method to obtain a statistical sample of 500 μm-risers and fully evaluate our selection inspecting different models of galaxy evolution. Methods. We consider one of the largest and deepest Herschel surveys, the Herschel Virgo Cluster Survey. We develop a novel selection algorithm which links the source extraction and spectral energy distribution fitting. To fully quantify selection biases we make end-to-end simulations including clustering and lensing. Results. We select 133 500 μm-risers over 55 deg2, imposing the criteria: S500 > S350 > S250, S250 > 13.2 mJy and S500 > 30 mJy. Differential number counts are in fairly good agreement with models, displaying a better match than other existing samples. The estimated fraction of strongly lensed sources is 24+6-5% based on models. Conclusions. We present the faintest sample of 500 μm-risers down to S250 = 13.2 mJy. We show that noise and strong lensing have an important impact on measured counts and redshift distribution of selected sources. We estimate the flux-corrected star formation rate density at 4 < z < 5 with the 500 μm-risers and find it to be close to the total value measured in far-infrared. This indicates that colour selection is not a limiting effect to search for the most massive, dusty z > 4 sources.

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Spectral energy distribution similarity of the local galaxies and the 3.6 μm selected galaxies from the Spitzer Extended Deep Survey

Research in Astronomy and Astrophysics ◽

10.1088/1674-4527/21/10/260 ◽

2021 ◽

Vol 21 (10) ◽

pp. 260

Author(s):

Cheng Cheng ◽

Jia-Sheng Huang ◽

Hai Xu ◽

Gao-Xiang Jin ◽

Chuan He ◽

...

Keyword(s):

High Redshift ◽

Spectral Energy Distribution ◽

Mass Function ◽

Spectral Energy ◽

Energy Distributions ◽

Mid Infrared ◽

Redshift Galaxy ◽

The Galaxy ◽

Deep Survey ◽

Multi Wavelength

Abstract The Spitzer Extended Deep Survey (SEDS) as a deep and wide mid-infrared (MIR) survey project provides a sample of 500 000+ sources spreading 1.46 square degree and a depth of 26 AB mag (3σ). Combining with the previous available data, we build a PSF-matched multi-wavelength photometry catalog from u band to 8 μm. We fit the SEDS galaxies spectral energy distributions by the local galaxy templates. The results show that the SEDS galaxy can be fitted well, indicating the high redshift galaxy (z ∼ 1) shares the same templates with the local galaxies. This study would facilitate the further study of the galaxy luminosity and high redshift mass function.

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The star formation properties of the observed and simulated AGN Universe: BAT versus EAGLE

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2414 ◽

2020 ◽

Vol 498 (2) ◽

pp. 2323-2338

Author(s):

Thomas M Jackson ◽

D J Rosario ◽

D M Alexander ◽

J Scholtz ◽

Stuart McAlpine ◽

...

Keyword(s):

Star Formation ◽

High Redshift ◽

Spectral Energy Distribution ◽

Formation Rate ◽

Host Galaxy ◽

Spectral Energy ◽

Host Galaxies ◽

X Ray ◽

Two Samples ◽

Stellar Masses

ABSTRACT In this paper, we present data from 72 low-redshift, hard X-ray selected active galactic nucleus (AGN) taken from the Swift–BAT 58 month catalogue. We utilize spectral energy distribution fitting to the optical to infrared photometry in order to estimate host galaxy properties. We compare this observational sample to a volume- and flux-matched sample of AGN from the Evolution and Assembly of GaLaxies and their Environments (EAGLE) hydrodynamical simulations in order to verify how accurately the simulations can reproduce observed AGN host galaxy properties. After correcting for the known +0.2 dex offset in the SFRs between EAGLE and previous observations, we find agreement in the star formation rate (SFR) and X-ray luminosity distributions; however, we find that the stellar masses in EAGLE are 0.2–0.4 dex greater than the observational sample, which consequently leads to lower specific star formation rates (sSFRs). We compare these results to our previous study at high redshift, finding agreement in both the observations and simulations, whereby the widths of sSFR distributions are similar (∼0.4–0.6 dex) and the median of the SFR distributions lie below the star-forming main sequence by ∼0.3–0.5 dex across all samples. We also use EAGLE to select a sample of AGN host galaxies at high and low redshift and follow their characteristic evolution from z = 8 to z = 0. We find similar behaviour between these two samples, whereby star formation is quenched when the black hole goes through its phase of most rapid growth. Utilizing EAGLE we find that 23 per cent of AGN selected at z ∼ 0 are also AGN at high redshift, and that their host galaxies are among the most massive objects in the simulation. Overall, we find EAGLE reproduces the observations well, with some minor inconsistencies (∼0.2 dex in stellar masses and ∼0.4 dex in sSFRs).

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Temporal correlation between the optical and γ-ray flux variations in the blazar 3C 454.3

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz941 ◽

2019 ◽

Vol 486 (2) ◽

pp. 1781-1795 ◽

Cited By ~ 8

Author(s):

Bhoomika Rajput ◽

C S Stalin ◽

S Sahayanathan ◽

Suvendu Rakshit ◽

Amit Kumar Mandal

Keyword(s):

Spectral Energy Distribution ◽

Broad Band ◽

Temporal Correlation ◽

Lorentz Factor ◽

Degree Of Polarization ◽

Spectral Energy ◽

Long Duration ◽

Γ Ray ◽

Optical Flux ◽

Optical Flare

ABSTRACT Blazars show optical and γ-ray flux variations that are generally correlated, although there are exceptions. Here we present anomalous behaviour seen in the blazar 3C 454.3 based on an analysis of quasi-simultaneous data at optical, ultraviolet, X-ray, and γ-ray energies, spanning about 9 yr from 2008 August to 2017 February. We have identified four time intervals (epochs), A, B, D, and E, when the source showed large-amplitude optical flares. In epochs A and B the optical and γ-ray flares are correlated, while in D and E corresponding flares in γ-rays are weak or absent. In epoch B the degree of optical polarization strongly correlates with changes in optical flux during a short-duration optical flare superimposed on one of long duration. In epoch E the optical flux and degree of polarization are anticorrelated during both the rising and declining phases of the optical flare. We carried out broad-band spectral energy distribution (SED) modelling of the source for the flaring epochs A,B, D, and E, and a quiescent epoch, C. Our SED modelling indicates that optical flares with absent or weak corresponding γ-ray flares in epochs D and E could arise from changes in a combination of parameters, such as the bulk Lorentz factor, magnetic field, and electron energy density, or be due to changes in the location of the γ-ray-emitting regions.

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Serendipitous discovery of an “ALMA-only” galaxy at 5 < z < 6 in an ALMA 3-mm survey

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320000605 ◽

2019 ◽

Vol 15 (S352) ◽

pp. 194-198

Author(s):

Christina C. Williams

Keyword(s):

Star Formation ◽

Energy Distribution ◽

Star Formation Rate ◽

High Redshift ◽

Spectral Energy Distribution ◽

Formation Rate ◽

Spectral Energy ◽

Large Contribution ◽

Massive Galaxies ◽

Multi Wavelength

AbstractWe discuss the serendipitous discovery of a dusty high-redshift galaxy in a small (8 arcmin2) ALMA 3-mm survey Williams et al. (2019). The galaxy was previously unknown and is absent from existing multi-wavelength catalogs (“ALMA-only”). Using the ALMA position as prior, we perform forced deblended photometry to constrain its spectral energy distribution. The spectral energy distribution is well described by a massive (M* = 1010.8 M⊙) and highly obscured (AV ∼ 4) galaxy at redshift z = 5.5 ± 1.1 with star formation rate ∼ 300 M⊙yr−1. Our small survey area implies an uncertain but large contribution to the cosmic star formation rate density, similar to the contribution from all ultraviolet-selected galaxies combined at this redshift. This galaxy likely traces an abundant population of massive galaxies absent from current samples of infrared-selected or sub-millimeter galaxies, but with larger space densities, higher duty cycles, and significant contribution to the cosmic star-formation rate and stellar mass densities.

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Cosmological models and the brightness profile of distant galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s174392131000966x ◽

2009 ◽

Vol 5 (H15) ◽

pp. 329-329

Author(s):

I. Olivares-Salaverri ◽

Marcelo B. Ribeiro

Keyword(s):

Cosmological Model ◽

Observational Data ◽

Galaxy Evolution ◽

Surface Brightness ◽

High Redshift ◽

Spectral Energy Distribution ◽

Surface Profile ◽

Galactic Evolution ◽

Spectral Energy ◽

Distant Galaxies

This work aims to determine the feasibility of an assumed cosmological model by means of a detailed analysis of the brightness profiles of distant galaxies. Starting from the theory of Ellis & Perry (1979) connecting the angular diameter distance obtained from a relativistic cosmological model and the detailed photometry of galaxies, we assume the presently most accepted cosmology with Λ ¬ = 0 and seek to predict the brightness profile of a galaxy in a given redshift z. To do so, we have to make assumptions concerning the galactic brightness structure and evolution, assuming a scenario where the specific emitted surface brightness Be,νe can be characterized as, Be,νe (r,z) = B0(z)J(νe,z)f[r(z)/a(z)]. Here r is the intrinsic galactic radius, νe the emitted frequency, B0(z) the central surface brightness, J(νe,z) the spectral energy distribution (SED), f[r(z)/a(z)] characterizes the shape of the surface profile distribution and a(z) is the scaling radius. The dependence on z is due to the galactic evolution. As spacetime curvature affects the received surface brightness, the reciprocity theorem (Ellis 1971) allows us to predict the theoretical received surface brightness. So, we are able to compare the theoretical surface brightness with its equivalent observational data already available for high redshift galaxies in order to test the consistency of the assumed cosmological model. The function f[r(z)/a(z)] is represented in the literature by various different shapes, like the Hubble, Hubble-Oemler and Abell-Mihalas single parameter profiles, characterizing the galactic surface brightness quite well when the disk or bulge dependence is dominant. Sérsic and core-Sérsic profiles use two or more parameters and reproduce the galactic profile almost exactly (Trujillo et al. 2004). If we consider all wavelengths, the theory tells us that the total intensity is equal to the surface brightness, so the chosen bandwidth should include most of the SED. In order to analyze only the effect of the cosmological model in the surface brightness and minimize evolutionary effects, we assume that there exists a homogeneous class of objects, whose properties are similar in all redshifts, allowing us to carry out comparisons at different values of z. Studying the parameters that affect the galactic evolution, as well as in others geometrical tests, we will be able to infer some possible galaxy evolution which could reproduce a theoretical surface brightness profile, in order to compare with the observational data and reach conclusions about the observational feasibility of the underlying cosmological model.

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Stellar Population Models

Proceedings of the International Astronomical Union ◽

10.1017/s174392131300505x ◽

2012 ◽

Vol 8 (S295) ◽

pp. 272-281 ◽

Cited By ~ 2

Author(s):

Claudia Maraston

Keyword(s):

Galaxy Formation ◽

Stellar Population ◽

High Redshift ◽

Spectral Energy Distribution ◽

Cosmic Time ◽

Mass Function ◽

Initial Mass Function ◽

Asymptotic Giant Branch ◽

Spectral Energy ◽

Massive Galaxies

AbstractModelling stellar populations in galaxies is a key approach to gain knowledge on the still elusive process of galaxy formation as a function of cosmic time. In this review, after a summary of the state-of-art, I discuss three aspects of the modelling, that are particularly relevant to massive galaxies, the focus of this symposium, at low and high-redshift. These are the treatment of the Thermally-Pulsating Asymptotic Giant Branch phase, evidences of an unusual Initial Mass Function, and the effect of modern stellar libraries on the model spectral energy distribution.

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GLACiAR, an Open-Source Python Tool for Simulations of Source Recovery and Completeness in Galaxy Surveys

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2018.17 ◽

2018 ◽

Vol 35 ◽

Cited By ~ 3

Author(s):

D. Carrasco ◽

M. Trenti ◽

S. Mutch ◽

P. A. Oesch

Keyword(s):

Hubble Space Telescope ◽

High Redshift ◽

Spectral Energy Distribution ◽

Software Tool ◽

Spectral Energy ◽

High Redshift Galaxies ◽

Galaxy Surveys ◽

Modelling Assumptions ◽

Number Counts ◽

Cosmic History

AbstractThe luminosity function is a fundamental observable for characterising how galaxies form and evolve throughout the cosmic history. One key ingredient to derive this measurement from the number counts in a survey is the characterisation of the completeness and redshift selection functions for the observations. In this paper, we present GLACiAR, an open python tool available on GitHub to estimate the completeness and selection functions in galaxy surveys. The code is tailored for multiband imaging surveys aimed at searching for high-redshift galaxies through the Lyman-break technique, but it can be applied broadly. The code generates artificial galaxies that follow Sérsic profiles with different indexes and with customisable size, redshift, and spectral energy distribution properties, adds them to input images, and measures the recovery rate. To illustrate this new software tool, we apply it to quantify the completeness and redshift selection functions for J-dropouts sources (redshift z ~ 10 galaxies) in the Hubble Space Telescope Brightest of Reionizing Galaxies Survey. Our comparison with a previous completeness analysis on the same dataset shows overall agreement, but also highlights how different modelling assumptions for the artificial sources can impact completeness estimates.

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A method for checking high-redshift identification of radio AGNs

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2132 ◽

2020 ◽

Vol 497 (2) ◽

pp. 2260-2264

Author(s):

Tao An ◽

Yingkang Zhang ◽

Sándor Frey

Keyword(s):

Large Scale ◽

High Redshift ◽

Lorentz Factor ◽

Jet Physics ◽

Automatic Identification ◽

Proper Motions ◽

Photometric Redshift ◽

Radio Jets ◽

Long Baseline ◽

Redshift Galaxy

ABSTRACT In large-scale optical spectroscopic surveys, there are many objects found to have multiple redshift measurements due to the weakness of their emission lines and the different automatic identification algorithms used. These include some suspicious high-redshift $(z \gtrsim 5)$ active galactic nuclei (AGNs). Here, we present a method for inspecting the high-redshift identification of such sources provided that they are radio-loud and have very long baseline interferometry (VLBI) imaging observations of their milli-arcsec (mas) scale jet structure available at multiple epochs. The method is based on the determination of jet component proper motions, and the fact that the combination of jet physics (the observed maximal values of the bulk Lorentz factor) and cosmology (the time dilation of observed phenomena in the early Universe) constrain the possible values of apparent proper motions. As an example, we present the case of the quasar J2346 + 0705 that was reported with two different redshifts, z1 = 5.063 and z2 = 0.171, in the literature. We measured the apparent proper motions (μ) of three components identified in its radio jet by utilizing VLBI data taken from 2014 to 2018. We obtained μJ1 = 0.334 ± 0.099 mas yr−1, μJ2 = 0.116 ± 0.029 mas yr−1, and μJ3 = 0.060 ± 0.005 mas yr−1. The maximal proper motion is converted to an apparent transverse speed of $\beta _{\rm app} = 41.2\pm 12.2\, c$, if the source is at redshift 5.063. This value exceeds the blazar jet speeds known to date. This and other arguments suggest that J2346 + 0705 is hosted by a low-redshift galaxy. Our method may be applicable for other high-redshift AGN candidates lacking unambiguous spectroscopic redshift determination or having photometric redshift estimates only, but showing prominent radio jets allowing for VLBI measurements of fast jet proper motions.

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