Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userChemical properties in the most distant radio galaxy
147
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present a deep optical spectrum of TN J0924-2201, the most distant radio galaxy at z = 5.19, obtained with FOCAS on the Subaru Telescope. We successfully detect, for the first time, the CIV1549 emission line from the narrow-line region (NLR). In addition to the emission-line fluxes of Ly alpha and CIV, we set upper limits on the NV and HeII emissions. We use these line detections and upper limits to constrain the chemical properties of TN J0924-2201. By comparing the observed emission-line flux ratios with photoionization models, we infer that the carbon-to-oxygen relative abundance is already [C/O] > -0.5 at a cosmic age of ~ 1.1 Gyr. This lower limit on [C/O] is higher than the ratio expected at the earliest phases of the galaxy chemical evolution, indicating that TN J0924-2201 has already experienced significant chemical evolution at z = 5.19.
rate research
Read More
We show that the most distant X-ray detected cluster known to date, ClJ1001 at z=2.506, hosts a strong overdensity of radio sources. Six of them are individually detected (within 10) in deep 0.75 resolution VLA 3GHz imaging, with S(3GHz)>8uJy. Of the six, AGN likely affects the radio emission in two galaxies while star formation is the dominant source powering the remaining four. We searched for cluster candidates over the full COSMOS 2-square degree field using radio-detected 3GHz sources and looking for peaks in Sigma5 density maps. ClJ1001 is the strongest overdensity by far with >10sigma, with a simple z_phot>1.5 preselection. A cruder photometric rejection of z<1 radio foregrounds leaves ClJ1001 as the second strongest overdensity, while even using all radio sources ClJ1001 remains among the four strongest projected overdensities. We conclude that there are great prospects for future, deep and wide-area radio surveys to discover large samples of the first generation of forming galaxy clusters. In these remarkable structures widespread star formation and AGN activity of massive galaxy cluster members, residing within the inner cluster core, will ultimately lead to radio continuum as one of the most effective means for their identification, with detection rates expected in the ballpark of 0.1-1 per square degree at z>2.5. Samples of hundreds such high-redshift clusters could potentially constrain cosmological parameters and test cluster and galaxy formation models.
The highest-redshift quasars are still rare and valuable objects for observational astrophysics and cosmology. They provide important constraints on the growth of the earliest supermassive black holes in the Universe, and information on the physical conditions in their environment. Among the nearly 60 quasars currently known at redshifts z>5.7, only a handful are strong emitters in radio continuum. These can be targets of sensitive high-resolution Very Long Baseline Interferometry (VLBI) observations to reveal their innermost structure, down to ~10 pc linear scales. We review the results of our earlier European VLBI Network (EVN) experiments on three of the most distant radio quasars known to date, and give a preliminary report on the EVN detection of a fourth one. The results obtained so far suggest that we see really young active galactic nuclei - not just in a cosmological sense but also in terms of their active life in radio.
We report the discovery of extended radio emission in the Phoenix cluster (SPT-CL J2344-4243, z=0.596) with the GMRT at 610 MHz. The diffuse emission extends over a region of at least 400-500 kpc and surrounds the central radio source of the Brightest Cluster Galaxy, but does not appear to be directly associated with it. We classify the diffuse emission as a radio mini-halo, making it the currently most distant mini-halo known. Radio mini-halos have been explained by synchrotron emitting particles re-accelerated via turbulence, possibly induced by gas sloshing generated from a minor merger event. Chandra observations show a non-concentric X-ray surface brightness distribution, which is consistent with this sloshing interpretation. The mini-halo has a flux density of $17pm5$ mJy, resulting in a 1.4 GHz radio power of ($10.4pm3.5) times 10^{24}$ W Hz$^{-1}$. The combined cluster emission, which includes the central compact radio source, is also detected in a shallow GMRT 156 MHz observation and together with the 610 MHz data we compute a spectral index of $-0.84pm0.12$ for the overall cluster radio emission. Given that mini-halos typically have steeper radio spectra than cluster radio galaxies, this spectral index should be taken as an upper limit for the mini-halo.
We present results from a 577 ks XMM-Newton observation of SPT-CL J0459-4947, the most distant cluster detected in the South Pole Telescope 2500 square degree (SPT-SZ) survey, and currently the most distant cluster discovered through its Sunyaev-Zeldovich effect. The data confirm the clusters high redshift, $z=1.71 pm 0.02$, in agreement with earlier, less precise optical/IR photometric estimates. From the gas density profile, we estimate a characteristic mass of $M_{500}=(1.8 pm 0.2) times 10^{14}M_{Sun}$; cluster emission is detected above the background to a radius of $sim 2.2 r_{500}$, or approximately the virial radius. The intracluster gas is characterized by an emission-weighted average temperature of $7.2 pm 0.3$ keV and metallicity with respect to Solar of $0.37 pm 0.08$. For the first time at such high redshift, this deep data set provides a measurement of metallicity outside the cluster center; at radii $r > 0.3 r_{500}$, we find it to be $0.33 pm 0.17$, in good agreement with precise measurements at similar radii in the most nearby clusters, supporting an early enrichment scenario in which the bulk of the cluster gas is enriched to a universal metallicity prior to cluster formation, with little to no evolution thereafter. The leverage provided by the high redshift of this cluster tightens by a factor of 2 constraints on evolving metallicity models, when combined with previous measurements at lower redshifts.
Blazars are a sub-class of quasars with Doppler boosted jets oriented close to the line of sight, and thus efficient probes of supermassive black hole growth and their environment, especially at high redshifts. Here we report on Very Long Baseline Interferometry observations of a blazar J0906+6930 at z = 5.47, which enabled the detection of polarised emission and measurement of jet proper motion at parsec scales. The observations suggest a less powerful jet compared with the general blazar population, including lower proper motion and bulk Lorentz factor. This coupled with a previously inferred high accretion rate indicate a transition from an accretion radiative power to a jet mechanical power based transfer of energy and momentum to the surrounding gas.While alternative scenarios could not be fully ruled out, our results indicate a possibly nascent jet embedded in and interacting with a dense medium resulting in a jet bending.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
