Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userEvidence for GN-z11 as a luminous galaxy at redshift 10.957
135
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
GN-z11 was photometrically selected as a luminous star-forming galaxy candidate at redshift z > 10 based on Hubble Space Telescope (HST) imaging data. Follow-up HST near-infrared grism observations detected a continuum break that was explained as the Ly-alpha break corresponding to z = 11.09 (+0.08-0.12). However, its accurate redshift remained unclear. Here we report a probable detection of three ultraviolet (UV) emission lines from GN-z11, which can be interpreted as the [C III] 1907, C III] 1909 doublet and O III] 1666 at z = 10.957+/-0.001 (when the Universe was only ~420 Myr old, or ~3% of its current age). This is consistent with the redshift of the previous grism observations, supporting GN-z11 as the most distant galaxy known to date. Its UV lines likely originate from dense ionized gas that is rarely seen at low redshifts, and its strong [C III] and C III] emission is partly due to an active galactic nucleus (AGN) or enhanced carbon abundance. GN-z11 is luminous and young, yet moderately massive, implying a rapid build-up of stellar mass in the past. Future facilities will be able to find the progenitors of such galaxies at higher redshift and probe the cosmic epoch in the beginning of re-ionization.
rate research
Read More
The recently discovered rapid transient GN-z11-flash has been suggested to be the prompt-emission ultraviolet flash associated with a gamma-ray burst serendipitously exploding in the ultra-high-$z$ galaxy GN-z11. We here place the flash into the context of the early ultraviolet emission of gamma-ray bursts, and find it is in agreement with the luminosity distribution of these events.
We discuss the possible interpretation of the recently observed transient, GN-z11-flash as originating from a shock-breakout in a Population III supernova occurring in the GN-z11 galaxy at $z sim 11$. We find that the parameters of the explosion are fully consistent with those expected from the shock breakout associated with a Type II supernova of a progenitor star of $sim 300$ solar masses in this galaxy, with of order unity such events expected over an observing timescale of a few years. We forecast the expected number of such transients from $z > 10$ galaxies as a function of their host stellar mass and star formation rate.
In Jiang et al. (2020), we reported a possible bright flash (hereafter GN-z11-flash) from a galaxy GN-z11 at z ~ 11. Recently, Steinhardt et al. (2021; arXiv:2101.12738) found 27 images with transient signals in Keck MOSFIRE archival data and claimed that GN-z11-flash was more likely from a moving object in our Solar system. We show that the Steinhardt et al.s definition of the chance probability and their methodology of finding GN-z11-flash-like transients are problematic in several aspects. In particular, none of their transients is analogous to GN-z11-flash, and none of them is positionally coincident with a known object in their imaging data. In Jiang et al., we performed a comprehensive analysis of the origin of GN-z11-flash and ruled out, to the best of our knowledge, the possibility of known man-made objects or moving objects in the Solar system, based on all available information and our current understanding of these objects. Steinhardt et al. did not use such information and did not analyse the GN-z11-flash event itself. The majority of their transients are apparently low-Earth orbit satellites or aircrafts. Therefore, their analysis can neither prove nor disprove our results. Finally, we present a method to estimate the chance probability of finding GN-z11-flash-like transients in archival data. Based on this method and the archival data used by Steinhardt et al., we obtain a loose upper limit of the probability that actually support the original results of Jiang et al. (2020).
Distant quasars are unique tracers to study the formation of the earliest supermassive black holes (SMBHs) and the history of cosmic reionization. Despite extensive efforts, only two quasars have been found at $zge7.5$, due to a combination of their low spatial density and the high contamination rate in quasar selection. We report the discovery of a luminous quasar at $z=7.642$, J0313$-$1806, the most distant quasar yet known. This quasar has a bolometric luminosity of $3.6times10^{13} L_odot$. Deep spectroscopic observations reveal a SMBH with a mass of $(1.6pm0.4) times10^9M_odot$ in this quasar. The existence of such a massive SMBH just $sim$670 million years after the Big Bang challenges significantly theoretical models of SMBH growth. In addition, the quasar spectrum exhibits strong broad absorption line (BAL) features in CIV and SiIV, with a maximum velocity close to 20% of the speed of light. The relativistic BAL features, combined with a strongly blueshifted CIV emission line, indicate that there is a strong active galactic nucleus (AGN) driven outflow in this system. ALMA observations detect the dust continuum and [CII] emission from the quasar host galaxy, yielding an accurate redshift of $7.6423 pm 0.0013$ and suggesting that the quasar is hosted by an intensely star-forming galaxy, with a star formation rate of $rmsim 200 ~M_odot ~yr^{-1}$ and a dust mass of $sim7times10^7~M_odot$. Followup observations of this reionization-era BAL quasar will provide a powerful probe of the effects of AGN feedback on the growth of the earliest massive galaxies.
We report on the second installment of an X-ray monitoring project of seven luminous radio-quiet quasars (RQQs). New {sl Chandra} observations of four of these, at $4.10leq zleq4.35$, yield a total of six X-ray epochs, per source, with temporal baselines of $sim850-1600$ days in the rest frame. These data provide the best X-ray light curves for RQQs at $z>4$, to date, enabling qualitative investigations of the X-ray variability behavior of such sources for the first time. On average, these sources follow the trend of decreasing variability amplitude with increasing luminosity, and there is no evidence for X-ray variability increasing toward higher redshifts, in contrast with earlier predictions of potential evolutionary scenarios. An ensemble variability structure function reveals that their variability level remains relatively flat across $approx20 - 1000$ days in the rest frame and it is generally lower than that of three similarly luminous RQQs at $1.33leq zleq 2.74$ over the same temporal range. We discuss possible explanations for the increased variability of the lower-redshift subsample and, in particular, whether higher accretion rates play a leading role. Near-simultaneous optical monitoring of the sources at $4.10leq zleq 4.35$ indicates that none is variable on $approx1$-day timescales, although flux variations of up to $sim25$% are observed on $approx100$-day timescales, typical of RQQs at similar redshifts. Significant optical-X-ray spectral slope variations observed in two of these sources are consistent with the levels observed in luminous RQQs and are dominated by X-ray variations.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
