scholarly journals The nature of faint radio galaxies at high redshifts

2019 ◽  
Vol 489 (4) ◽  
pp. 5053-5075 ◽  
Author(s):  
A Saxena ◽  
H J A Röttgering ◽  
K J Duncan ◽  
G J Hill ◽  
P N Best ◽  
...  
Keyword(s):  
Near Infrared ◽  
High Redshift ◽  
Radio Galaxies ◽  
Star Forming ◽  
Inverse Compton Scattering ◽  
Inverse Compton ◽  
Order Of Magnitude ◽  
Stellar Masses ◽  
Scattering Losses ◽  
Rule Out

ABSTRACT We present spectra and near-infrared images of a sample of faint radio sources initially selected as promising high-redshift radio galaxy (HzRG) candidates. We have determined redshifts for a total of 13 radio galaxies with redshifts ranging from 0.52 ≤ $z$ ≤ 5.72. Our sample probes radio luminosities that are almost an order of magnitude fainter than previous large samples at the highest redshifts. We use near-infrared photometry for a subsample of these galaxies to calculate stellar masses using simple stellar population models, and find stellar masses to be in the range $10^{10.8} {--}10^{11.7} \, \mathrm{M}_\odot$. We then compare our faint radio galaxies with brighter radio galaxies at $z$ ≥ 2 from the literature. We find that fainter radio galaxies have lower Ly α luminosities and narrower line widths compared to the bright ones, implying photoionization by a weaker active galactic nucleus (AGN). We also rule out the presence of strong shocks in faint HzRGs. The stellar masses determined for faint HzRGs are lower than those observed for brighter ones. We find that faint HzRG population in the redshift range 2–4 forms a bridge between star-forming and narrow-line AGNs, whereas the ones at $z$ > 4 are likely to be dominated by star formation, and may be building up their stellar mass through cold accretion of gas. Finally, we show that the overall redshift evolution of radio sizes at $z$ > 2 is fully compatible with increased inverse Compton scattering losses at high redshifts.

scholarly journals A near-infrared morphological comparison of high-redshift submillimetre and radio galaxies: massive star-forming discs versus relaxed spheroids

2011 ◽  
Vol 412 (1) ◽  
pp. 295-317 ◽  
Author(s):  
Thomas A. Targett ◽  
James S. Dunlop ◽  
Ross J. McLure ◽  
Philip N. Best ◽  
Michele Cirasuolo ◽  
...  
Keyword(s):  
Massive Star ◽  
Near Infrared ◽  
High Redshift ◽  
Radio Galaxies ◽  
Morphological Comparison ◽  
Star Forming

scholarly journals Euclid preparation

2020 ◽  
Vol 642 ◽  
pp. A192 ◽  
Author(s):  
◽  
V. Guglielmo ◽  
R. Saglia ◽  
F. J. Castander ◽  
A. Galametz ◽  
...  
Keyword(s):  
Near Infrared ◽  
Current Knowledge ◽  
High Redshift ◽  
Stage Iv ◽  
Weak Lensing ◽  
Success Rates ◽  
Spectroscopic Measurements ◽  
Star Forming ◽  
The Galaxy ◽  
Stellar Masses

The Complete Calibration of the Colour–Redshift Relation survey (C3R2) is a spectroscopic effort involving ESO and Keck facilities designed specifically to empirically calibrate the galaxy colour–redshift relation – P(z|C) to the Euclid depth (iAB = 24.5) and is intimately linked to the success of upcoming Stage IV dark energy missions based on weak lensing cosmology. The aim is to build a spectroscopic calibration sample that is as representative as possible of the galaxies of the Euclid weak lensing sample. In order to minimise the number of spectroscopic observations necessary to fill the gaps in current knowledge of the P(z|C), self-organising map (SOM) representations of the galaxy colour space have been constructed. Here we present the first results of an ESO@VLT Large Programme approved in the context of C3R2, which makes use of the two VLT optical and near-infrared multi-object spectrographs, FORS2 and KMOS. This data release paper focuses on high-quality spectroscopic redshifts of high-redshift galaxies observed with the KMOS spectrograph in the near-infrared H- and K-bands. A total of 424 highly-reliable redshifts are measured in the 1.3 ≤ z ≤ 2.5 range, with total success rates of 60.7% in the H-band and 32.8% in the K-band. The newly determined redshifts fill 55% of high (mainly regions with no spectroscopic measurements) and 35% of lower (regions with low-resolution/low-quality spectroscopic measurements) priority empty SOM grid cells. We measured Hα fluxes in a 1.″2 radius aperture from the spectra of the spectroscopically confirmed galaxies and converted them into star formation rates. In addition, we performed an SED fitting analysis on the same sample in order to derive stellar masses, E(B − V), total magnitudes, and SFRs. We combine the results obtained from the spectra with those derived via SED fitting, and we show that the spectroscopic failures come from either weakly star-forming galaxies (at z <  1.7, i.e. in the H-band) or low S/N spectra (in the K-band) of z >  2 galaxies.

scholarly journals Using ALMA to resolve the nature of the early star-forming large-scale structure PLCK G073.4−57.5

2019 ◽  
Vol 625 ◽  
pp. A96 ◽  
Author(s):  
Rüdiger Kneissl ◽  
Maria del Carmen Polletta ◽  
Clement Martinache ◽  
Ryley Hill ◽  
Benjamin Clarenc ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Clusters ◽  
Large Scale ◽  
Near Infrared ◽  
High Redshift ◽  
Photometric Redshifts ◽  
Star Forming ◽  
Multi Wavelength ◽  
The Individual ◽  
Stellar Masses

Galaxy clusters at high redshift are key targets for understanding matter assembly in the early Universe, yet they are challenging to locate. A sample of more than 2000 high-z candidate structures has been found using Planck’s all-sky submillimetre maps, and a sub-set of 234 have been followed up with Herschel-SPIRE, which showed that the emission can be attributed to large overdensities of dusty star-forming galaxies. As a next step, we need to resolve and characterise the individual galaxies giving rise to the emission seen by Planck and Herschel, and to find out whether they constitute the progenitors of present-day, massive galaxy clusters. Thus, we targeted the eight brightest Herschel-SPIRE sources in the centre of the Planck peak PLCK G073.4−57.5 using ALMA at 1.3 mm, and complemented these observations with multi-wavelength data from Spitzer-IRAC, CFHT-WIRCam in the J and Ks bands, and JCMT’s SCUBA-2 instrument. We detected a total of 18 millimetre galaxies brighter than 0.3 mJy within the 2.4 arcmin2 ALMA pointings, corresponding to an ALMA source density 8–30 times higher than average background estimates and larger than seen in typical “proto-cluster” fields. We were able to match all but one of the ALMA sources to a near infrared (NIR) counterpart. The four most significant SCUBA-2 sources are not included in the ALMA pointings, but we find an 8σ stacking detection of the ALMA sources in the SCUBA-2 map at 850 μm. We derive photometric redshifts, infrared (IR) luminosities, star-formation rates (SFRs), stellar masses (ℳ), dust temperatures, and dust masses for all of the ALMA galaxies. Photometric redshifts identify two groups each of five sources, concentrated around z  ≃  1.5 and 2.4. The two groups show two “red sequences”, that is similar near-IR [3.6]  −  [4.5] colours and different J  −  Ks colours. The majority of the ALMA-detected galaxies are on the SFR versus ℳ main sequence (MS), and half of the sample is more massive than the characteristic ℳ* at the corresponding redshift. We find that the z  ≃  1.5 group has total SFR = 840−100+120 M⊙ yr−1 and ℳ = 5.8−2.4+1.7 × 1011 M⊙, and that the z  ≃  2.4 group has SFR = 1020−170+310 M⊙ yr−1 and ℳ = 4.2−2.1+1.5 × 1011 M⊙, but the latter group is more scattered in stellar mass and around the MS. Serendipitous CO line detections in two of the galaxies appear to match their photometric redshifts at z  =  1.54. We performed an analysis of star-formation efficiencies (SFEs) and CO- and mm-continuum-derived gas fractions of our ALMA sources, combined with a sample of 1 <  z <  3 cluster and proto-cluster members, and observed trends in both quantities with respect to stellar masses and in comparison to field galaxies.

Cold gas studies of a z = 2.5 protocluster

2020 ◽  
Vol 15 (S359) ◽  
pp. 136-140
Author(s):  
Minju M. Lee ◽  
Ichi Tanaka ◽  
Rohei Kawabe
Keyword(s):  
Galaxy Evolution ◽  
High Redshift ◽  
Kinematic Model ◽  
Molecular Gas ◽  
General View ◽  
Massive Galaxies ◽  
Star Forming ◽  
Gas Kinematics ◽  
Narrow Band Filter ◽  
Stellar Masses

AbstractWe present studies of a protocluster at z =2.5, an overdense region found close to a radio galaxy, 4C 23.56, using ALMA. We observed 1.1 mm continuum, two CO lines (CO (4–3) and CO (3–2)) and the lower atomic carbon line transition ([CI](3P1-3P0)) at a few kpc (0″.3-0″.9) resolution. The primary targets are 25 star-forming galaxies selected as Hα emitters (HAEs) that are identified with a narrow band filter. These are massive galaxies with stellar masses of > 1010Mʘ that are mostly on the galaxy main sequence at z =2.5. We measure the molecular gas mass from the independent gas tracers of 1.1 mm, CO (3–2) and [CI], and investigate the gas kinematics of galaxies from CO (4–3). Molecular gas masses from the different measurements are consistent with each other for detection, with a gas fraction (fgas = Mgas/(Mgas+ Mstar)) of ≃ 0.5 on average but with a caveat. On the other hand, the CO line widths of the protocluster galaxies are typically broader by ˜50% compared to field galaxies, which can be attributed to more frequent, unresolved gas-rich mergers and/or smaller sizes than field galaxies, supported by our high-resolution images and a kinematic model fit of one of the galaxies. We discuss the expected scenario of galaxy evolution in protoclusters at high redshift but future large surveys are needed to get a more general view.

scholarly journals Planck’s dusty GEMS

2018 ◽  
Vol 620 ◽  
pp. A60 ◽  
Author(s):  
R. Cañameras ◽  
N. P. H. Nesvadba ◽  
M. Limousin ◽  
H. Dole ◽  
R. Kneissl ◽  
...  
Keyword(s):  
Star Formation ◽  
Near Infrared ◽  
Infrared Imaging ◽  
High Redshift ◽  
Dust Emission ◽  
Galaxy Cluster ◽  
Star Forming ◽  
The Galaxy ◽  
Mass Outflow ◽  
Gas Accretion

We report the discovery of a molecular wind signature from a massive intensely star-forming clump of a few 109 M⊙, in the strongly gravitationally lensed submillimeter galaxy “the Emerald” (PLCK_G165.7+49.0) at z = 2.236. The Emerald is amongst the brightest high-redshift galaxies on the submillimeter sky, and was initially discovered with the Planck satellite. The system contains two magnificient structures with projected lengths of 28.5″ and 21″ formed by multiple, near-infrared arcs, falling behind a massive galaxy cluster at z = 0.35, as well as an adjacent filament that has so far escaped discovery in other wavebands. We used HST/WFC3 and CFHT optical and near-infrared imaging together with IRAM and SMA interferometry of the CO(4–3) line and 850 μm dust emission to characterize the foreground lensing mass distribution, construct a lens model with LENSTOOL, and calculate gravitational magnification factors between 20 and 50 in most of the source. The majority of the star formation takes place within two massive star-forming clumps which are marginally gravitationally bound and embedded in a 9 × 1010 M⊙, fragmented disk with 20% gas fraction. The stellar continuum morphology is much smoother and also well resolved perpendicular to the magnification axis. One of the clumps shows a pronounced blue wing in the CO(4–3) line profile, which we interpret as a wind signature. The mass outflow rates are high enough for us to suspect that the clump might become unbound within a few tens of Myr, unless the outflowing gas can be replenished by gas accretion from the surrounding disk. The velocity offset of –200 km s−1 is above the escape velocity of the clump, but not that of the galaxy overall, suggesting that much of this material might ultimately rain back onto the galaxy and contribute to fueling subsequent star formation.

scholarly journals Optical and IR Properties of Radio Galaxies as a Function of their Radio Power

1996 ◽  
Vol 171 ◽  
pp. 414-414
Author(s):  
L. Maxfield ◽  
S.G. Djorgovski ◽  
D. Thompson ◽  
M.A. Pahre ◽  
R.R. de Carvalho ◽  
...  
Keyword(s):  
High Redshift ◽  
Spectroscopic Properties ◽  
Radio Galaxies ◽  
Active Nucleus ◽  
Data Set ◽  
Uv Emission ◽  
Two Samples ◽  
Order Of Magnitude ◽  
Ir Photometry ◽  
Radio Power

We compare optical and infrared photometric and spectroscopic properties of high-redshift radio galaxies from the 3CR and B3 surveys. At a given redshift and a fixed restframe frequency, the two samples differ on average by an order of magnitude in radio power, thus providing a fair baseline in radio powerfor a range of redshifts. We present new optical and IR photometry and spectrosopy for a number of B3 sources. We combine these data with the existing corresponding information on B3 and 3CR sources, in order to explore different correlations of source properties with redshift, and among themselves. B3 sources follow the same trend as 3CR's in the K band Hubble diagram, although they do seem to be slightly fainter on average at a given redshift. This trend is slightly more prominent in the Gunn r band. This suggests that some fraction of the observed light in the r and K bands is contributed by an active nucleus, which also powers the radio lobes. The B3's also tend to have lower emission line luminosities than 3CR's at any given redshift, suggesting that there may be a correlation between line luminosity and radio power. Such a correlation is clearly seen and is followed by both samples. It suggests that the UV emission lines are largely powered by the active nucleus, ostensibly a hidden quasar, which is also responsible for the radio emission. We also examine the behavior of the optical and radio PA alignments for the combined B3+3CR data set. We find that high-power and high-redshift subsamples for both B3's and 3CR's show the alignments more prominently, but we still cannot tell which of these variables dominates this effect. This work was supported in part by the NSF PYI award AST-9157412, and the Bressler Foundation.

scholarly journals The potential of using KMOS for multi-object massive star spectroscopy

2016 ◽  
Vol 12 (S329) ◽  
pp. 454-454
Author(s):  
Michael Wegner ◽  
Ralf Bender ◽  
Ray Sharples ◽  
Keyword(s):  
Galaxy Formation ◽  
Near Infrared ◽  
High Redshift ◽  
High Mass ◽  
Galactic Centre ◽  
Star Forming ◽  
Star Forming Regions ◽  
Spectral Bands ◽  
Galaxy Formation And Evolution ◽  
Potential Applications

AbstractKMOS, the “K-Band Multi-Object Spectrometer”, was built by a British-German consortium as a second generation instrument for the ESO Paranal Observatory. It is available to the user community since its successful commissioning in 2013 (Sharples et al. 2013). As a multi-object integral field spectrometer for the near infrared, KMOS offers 24 deployable IFUs of 2.8x2.8 arcsec and 14x14 spatial pixels each, which can either be placed individually within a 7.2 arcmin field of view or combined in a Mosaic mode in order to map contiguous fields on sky. The instrument covers the whole range of NIR atmospheric windows (0.8. . .2.5μm) with 5 spectral bands and a resolution of R ≈ 3000. . .4000.Although the main science driver for KMOS was to enable the study of galaxy formation and evolution through multiplexed observations of high-redshift galaxies, KMOS also already exhibited its tremendous potential for the spectroscopy of massive stars: A quantitative study of 27 RSGs in NGC 300 (Gazak et al. 2015) proves its applicability for the spectroscopy of individual stars even beyond the Local Group. A Mosaic observation of the Galactic centre (Feldmeier-Krause et al. 2015) demonstrates how spectra of early-type stars can be extracted from a contiguous field. Other applications include (but need not be limited to) velocity determinations of globular cluster stars, observations of jets/outflows of high mass protostars, or contiguous mapping of star-forming regions.We therefore aim at presenting the excellent capabilities of KMOS to a wider community and indicate potential applications.

scholarly journals X-shooter and ALMA spectroscopy of GRB 161023A

2018 ◽  
Vol 620 ◽  
pp. A119 ◽  
Author(s):  
A. de Ugarte Postigo ◽  
C. C. Thöne ◽  
J. Bolmer ◽  
S. Schulze ◽  
S. Martín ◽  
...  
Keyword(s):  
Near Infrared ◽  
Gamma Ray ◽  
High Redshift ◽  
Nir Spectroscopy ◽  
Host Galaxy ◽  
Star Forming ◽  
Star Forming Regions ◽  
Molecular Features ◽  
Short Period ◽  
Luminous Objects

Context. Long gamma-ray bursts (GRBs) are produced during the dramatic deaths of massive stars with very short lifetimes, meaning that they explode close to the birth place of their progenitors. Over a short period they become the most luminous objects observable in the Universe, being perfect beacons to study high-redshift star-forming regions. Aims. We aim to use the afterglow of GRB 161023A at a redshift z = 2.710 as a background source to study the environment of the explosion and the intervening systems along its line of sight. Methods. For the first time, we complement ultraviolet (UV), optical and near-infrared (NIR) spectroscopy with millimetre spectroscopy using the Atacama Large Millimeter Array (ALMA), which allows us to probe the molecular content of the host galaxy. The X-shooter spectrum shows a plethora of absorption features including fine-structure and metastable transitions of Fe, Ni, Si, C, and O. We present photometry ranging from 43 s to over 500 days after the burst. Results. We infer a host-galaxy metallicity of [Zn/H] = −1.11 ± 0.07, which, corrected for dust depletion, results in [X/H] = −0.94 ± 0.08. We do not detect molecular features in the ALMA data, but we derive limits on the molecular content of log(NCO/cm−2) < 15.7 and log(NHCO+/cm−-12, which are consistent with those that we obtain from the optical spectra, log(NH2/cm−2)< 15.2 and log(NCO/cm−2) < 14.5. Within the host galaxy, we detect three velocity systems through UV, optical and NIR absorption spectroscopy, all with levels that were excited by the GRB afterglow. We determine the distance from these systems to the GRB to be in the range between 0.7 and 1.0 kpc. The sight line to GRB 161023A shows nine independent intervening systems, most of them with multiple components. Conclusions. Although no molecular absorption was detected for GRB 161023A, we show that GRB millimetre spectroscopy is now feasible and is opening a new window on the study of molecular gas within star-forming galaxies at all redshifts. The most favoured lines of sight for this purpose will be those with high metallicity and dust.

scholarly journals Molecular gas, stars, and dust in sub-L⋆ star-forming galaxies at z ~ 2: Evidence for universal star formation and non-universal dust-to-gas ratio

2015 ◽  
Vol 11 (S315) ◽  
pp. 254-257
Author(s):  
Miroslava Dessauges-Zavadsky ◽  
Michel Zamojski ◽  
Daniel Schaerer ◽  
Françoise Combes ◽  
Eiichi Egami ◽  
...  
Keyword(s):  
Star Formation ◽  
Gravitational Lensing ◽  
High Redshift ◽  
Clear Trend ◽  
Star Forming ◽  
Solar Metallicity ◽  
Stellar Masses ◽  
Formation Efficiency ◽  
Gas Ratio ◽  
Single Relation

AbstractCurrent star-forming galaxies (SFGs) with CO measurements at z ~ 2 suffer from a bias toward high star formation rates (SFR) and high stellar masses (M*). It is yet essential to extend the CO measurements to the more numerous z ~ 2 SFGs with LIR < L⋆ = 4× 1011 L⊙ and M* < 2.5× 1010 M⊙. We have achieved CO, stars, and dust measurements in 8 such sub-L⋆ SFGs with the help of gravitational lensing. Combined with CO-detected galaxies from the literature, we find that the LIR, L′CO(1−0) data are best-fitted with a single relation that favours a universal star formation. This picture emerges because of the enlarged star formation efficiency spread of the current z>1 SFGs sample. We show that this spread is mostly triggered by the combination of redshift, specific SFR, and M*. Finally, we find evidence for a non-universal dust-to-gas ratio (DGR) with a clear trend for a lower DGR mean in z>1 SFGs by a factor of 2 with respect to local galaxies and high-redshift sub-mm galaxies at fixed about solar metallicity.

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