Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMolecular Gas in the Halo Fuels the Growth of a Massive Cluster Galaxy at High Redshift
80
0
0.0
(
0
)
Authors
B.H.C. Emonts
Ask ChatGPT about the research
No Arabic abstract
The largest galaxies in the Universe reside in galaxy clusters. Using sensitive observations of carbon-monoxide, we show that the Spiderweb Galaxy -a massive galaxy in a distant protocluster- is forming from a large reservoir of molecular gas. Most of this molecular gas lies between the protocluster galaxies and has low velocity dispersion, indicating that it is part of an enriched inter-galactic medium. This may constitute the reservoir of gas that fuels the widespread star formation seen in earlier ultraviolet observations of the Spiderweb Galaxy. Our results support the notion that giant galaxies in clusters formed from extended regions of recycled gas at high redshift.
rate research
Read More
We perform simulations of the capabilities of the next generation Very Large Array in the context of imaging low order CO emission from typical high redshift star forming galaxies at ~ 1 kpc resolution. We adopt as a spatial and dynamical template the CO 1-0 emission from M 51, scaled accordingly for redshift, transition, and total gas mass. The molecular gas masses investigated are factors of 1.4, 3.5, and 12.5 larger that of M 51, at z = 0.5, 2, and 4.2, respectively. The z = 2 galaxy gas mass is comparable to the lowest mass galaxies currently being discovered in the deepest ALMA and NOEMA cosmological CO line surveys, corresponding to galaxies with star formation rates ~ 10 to 100 $M_odot$ yr$^{-1}$. The ngVLA will perform quality imaging at 1kpc resolution of the gas distribution and dynamics over this disk. We recover the overall rotation curve, galaxy orientation properties, and molecular ISM internal velocity dispersion. The model at z = 4.2 corresponds to a massive star forming main sequence disk (SFR ~ 130 $M_odot$ yr$^{-1}$). The ngVLA can obtain 1kpc resolution images of such a system in a reasonable integration time, and recover the basic galaxy orientation parameters, and, asymptotically, the maximum rotation velocity. We compare the ngVLA results with capabilities of ALMA and the Jansky VLA. ALMA and the VLA can detect the integrated low order CO emission from these galaxies, but lack the sensitivity to perform the high resolution imaging to recover the dynamics at 1kpc scales. To do so would require of order 1000 hrs per galaxy with these current facilities. We investigate a minimal ngVLA configuration, removing the longest baselines and much of the very compact core, and find good imaging can still be performed at 1 kpc resolution.
In this Letter, we report the discovery of a radio halo in the high-redshift galaxy cluster PSZ2 G099.86+58.45 ($z=0.616$) with the LOw Frequency ARray (LOFAR) at 120-168 MHz. This is one of the most distant radio halos discovered so far. The diffuse emission extends over $sim$ 1 Mpc and has a morphology similar to that of the X-ray emission as revealed by XMM-Newton data. The halo is very faint at higher frequencies and is barely detected by follow-up 1-2 GHz Karl G.~Jansky Very Large Array (JVLA) observations, which enable us to constrain the radio spectral index to be $alphaleq 1.5-1.6$, i.e.; with properties between canonical and ultra-steep spectrum radio halos. Radio halos are currently explained as synchrotron radiation from relativistic electrons that are re-accelerated in the intra-cluster medium (ICM) by turbulence driven by energetic mergers. We show that in such a framework radio halos are expected to be relatively common at $sim150$ MHz ($sim30-60%$) in clusters with mass and redshift similar to PSZ2 G099.86+58.45; however, at least 2/3 of these radio halos should have steep spectrum and thus be very faint above $sim 1$ GHz frequencies. Furthermore, since the luminosity of radio halos at high redshift depends strongly on the magnetic field strength in the hosting clusters, future LOFAR observations will also provide vital information on the origin and amplification of magnetic fields in galaxy clusters.
We present a new study of archival ALMA observations of the CO(2-1) line emission of the host galaxy of quasar RX J1131 at redshift $z$=0.654, lensed by a foreground galaxy. A simple lens model is shown to well reproduce the optical images obtained by the Hubble Space Telescope. Clear evidence for rotation of the gas contained in the galaxy is obtained and a simple rotating disc model is shown to give an excellent overall description of the morpho-kinematics of the source. The possible presence of a companion galaxy suggested by some previous authors is not confirmed. Detailed comparison between model and observations gives evidence for a more complex dynamics than implied by the model. Doppler velocity dispersion within the beam size in the image plane is found to account for the observed line width.
According to the current understanding of cosmic structure formation, the precursors of the most massive structures in the Universe began to form shortly after the Big Bang, in regions corresponding to the largest fluctuations in the cosmic density field. Observing these structures during their period of active growth and assembly - the first few hundred million years of the Universe - is challenging because it requires surveys that are sensitive enough to detect the distant galaxies that act as signposts for these structures and wide enough to capture the rarest objects. As a result, very few such objects have been detected so far. Here we report observations of a far-infrared-luminous object at redshift 6.900 (less than 800 Myr after the Big Bang) that was discovered in a wide-field survey. High-resolution imaging reveals this source to be a pair of extremely massive star-forming galaxies. The larger of these galaxies is forming stars at a rate of 2900 solar masses per year, contains 270 billion solar masses of gas and 2.5 billion solar masses of dust, and is more massive than any other known object at a redshift of more than 6. Its rapid star formation is probably triggered by its companion galaxy at a projected separation of just 8 kiloparsecs. This merging companion hosts 35 billion solar masses of stars and has a star-formation rate of 540 solar masses per year, but has an order of magnitude less gas and dust than its neighbor and physical conditions akin to those observed in lower-metallicity galaxies in the nearby Universe. These objects suggest the presence of a dark-matter halo with a mass of more than 400 billion solar masses, making it among the rarest dark-matter haloes that should exist in the Universe at this epoch.
Based on ALMA Band 3 observations of the CO(2-1) line transition, we report the discovery of three new gas-rich (M_H2 ~ 1.5-4.8 x 10^10 M_sun, SFRs in the range ~5-100 M_sun/yr) galaxies in an overdense region at z=1.7, that already contains eight spectroscopically confirmed members. This leads to a total of 11 confirmed overdensity members, within a projected distance of ~ 1.15 Mpc and in a redshift range of Dz = 0.012. Under simple assumptions, we estimate that the system has a total mass of >= 3-6 x 10^13 M_sun, and show that it will likely evolve into a >~ 10^14 M_sun cluster at z = 0. The overdensity includes a powerful Compton-thick Fanaroff-Riley type II (FRII) radio-galaxy, around which we discovered a large molecular gas reservoir (M_H2 ~ 2 x 10^11 M_sun). We fitted the FRII resolved CO emission with a 2-D Gaussian model with major (minor) axis of ~ 27 (~ 17) kpc, that is a factor of ~3 larger than the optical rest-frame emission. Under the assumption of a simple edge-on disk morphology, we find that the galaxy interstellar medium produces a column density towards the nucleus of ~ 5.5 x 10^23 cm^-2. Such a dense ISM may then contribute significantly to the total nuclear obscuration measured in the X-rays (N_(H,X) ~ 1.5 x 10^24 cm^-2) in addition to a small, pc-scale absorber around the central engine. The velocity map of this source unveils a rotational motion of the gas that is perpendicular to the radio-jets. The FRII is located at the center of the projected spatial distribution of the structure members, and its velocity offset from the peak of the redshift distribution is well within the structures velocity dispersion. All this, coupled with the large amount of gas around the FRII, its stellar mass of ~ 3 x 10^11 M_sun, SFR of ~ 200-600 M_sun/yr, and powerful radio-to-X-ray emission, suggests that this source is the likely progenitor of the future brightest cluster galaxy.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
