Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userOutflows from dwarf starbursts are ubiquitous: kinematics of z<0.3 GRB-SN hosts resolved with FLAMES
57
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The hosts of long duration gamma-ray bursts are predominantly starburst galaxies at subsolar metallicity. At redshifts z<1, this implies that most of them are low-mass dwarf galaxies similar to the populations of blue compact dwarfs and dwarf irregulars. What triggers the massive star-formation needed for producing a GRB progenitor is still largely unknown, as are the resolved gas properties and kinematics of these galaxies and their formation history. Here we present a sample of six spatially resolved GRB hosts at z<0.3 observed with 3D spectroscopy at high spectral resolution (R=8,000-13,000) using FLAMES/VLT. We analyze the resolved gas kinematics in the full and the abundances in a subsample. Only two galaxies show a regular disk-like rotation field, two are dispersion dominated and the others have several narrow emission components associated with different parts of the galaxy, which might indicate recent mergers. All galaxies show evidence for broad components underlying the main narrow emission with FWHM of 150-300 km/s. This broad component is more metal rich than the narrow components, blueshifted and follows a different velocity structure. We find a weak correlation between the star-formation rate and the FHWM of the broad component, its flux relative to the narrow component and the maximum outflow velocity of the gas, but we not find any correlation with the star-formation density, metallicity or stellar mass. We associate this broad component with a metal rich outflow from star-forming regions in the host. The GRB is not found at the brightest or most extreme region of the host but is always associated with a star-forming region showing a clear wind component. Our study shows the great potential of 3D spectroscopy to study the star-formation processes in galaxies hosting extreme transients, the need for high S/N and the dangers using un- or only partially resolved data.
rate research
Read More
The redshift distribution of gamma-ray bursts (GRBs) is strongly biased by selection effects. We investigate, via Monte Carlo simulations, one possible selection effect that may be modifying the Swift GRB redshift distribution. We show how telescope response times to acquire a GRB redshift may, via the Malmquist effect and GRB optical afterglow brightness distribution, introduce a bias into the average of the observed redshift distribution. It is difficult to reconcile a recently reported correlated trend between telescope response time and average redshifts unless we employ a redshift-dependent optical afterglow distribution. Simulations of this selection effect suggest that GRB optical afterglows may have been either intrinsically brighter early in the Universe or suffered less local host galaxy extinction.
The number of supernovae known to be connected with long-duration gamma-ray bursts is increasing and the link between these events is no longer exclusively found at low redshift ($z lesssim 0.3$) but is well established also at larger distances. We present a new case of such a liaison at $z = 0.33$ between GRB,171010A and SN,2017htp. It is the second closest GRB with an associated supernova of only three events detected by Fermi-LAT. The supernova is one of the few higher redshift cases where spectroscopic observations were possible and shows spectral similarities with the well-studied SN,1998bw, having produced a similar Ni mass ($M_{rm Ni}=0.33pm0.02 ~rm{M_{odot}}$) with slightly lower ejected mass ($M_{rm ej}=4.1pm0.7~rm{M_{odot}}$) and kinetic energy ($E_{rm K} = 8.1pm2.5 times 10^{51} ~rm{erg}$). The host-galaxy is bigger in size than typical GRB host galaxies, but the analysis of the region hosting the GRB revealed spectral properties typically observed in GRB hosts and showed that the progenitor of this event was located in a very bright HII region of its face-on host galaxy, at a projected distance of $sim$ 10 kpc from its galactic centre. The star-formation rate (SFR$_{GRB} sim$ 0.2 M$_{odot}$~yr$^{-1}$) and metallicity (12 + log(O/H) $sim 8.15 pm 0.10$) of the GRB star-forming region are consistent with those of the host galaxies of previously studied GRB-SN systems.
We study the properties of the galaxies hosting the first 19 tidal disruption events (TDEs) detected with the Zwicky Transient Facility (ZTF) within the context of a carefully constructed, representative host galaxy sample. We find that the ZTF sample of TDE hosts is dominated by compact green valley galaxies. After we restrict the comparison sample to galaxies with a similar concentration, as measured by Sersic index, we find this green valley over representation is even larger. That is, concentrated red sequence galaxies are not producing TDEs at elevated levels. We present host galaxy spectra which show that E+A galaxies are overrepresented in the ZTF sample by a factor of $approx$22, which is lower than previous TDE host galaxy studies have found. We find that this overrepresentation can be fully accounted for when taking into account the masses, colors, and Sersic indices of the ZTF TDE hosts. The combination of both green colors and high Sersic index of the typical TDE host galaxy could be explained if the TDE rate is temporarily enhanced following a merger that leads to a higher central concentration of stars.
We study Brightest Cluster Galaxies (BCGs) in $sim5000$ galaxy clusters from the Hyper Suprime-Cam (HSC) Subaru Strategic Program. The sample is selected over an area of 830 $textrm{deg}^2$ and is uniformly distributed in redshift over the range $z=0.3-1.0$. The clusters have stellar masses in the range $10^{11.8} - 10^{12.9} M_{odot}$. We compare the stellar mass of the BCGs in each cluster to what we would expect if their masses were drawn from the mass distribution of the other member galaxies of the clusters. The BCGs are found to be special, in the sense that they are not consistent with being a statistical extreme of the mass distribution of other cluster galaxies. This result is robust over the full range of cluster stellar masses and redshifts in the sample, indicating that BCGs are special up to a redshift of $z=1.0$. However, BCGs with a large separation from the center of the cluster are found to be consistent with being statistical extremes of the cluster member mass distribution. We discuss the implications of these findings for BCG formation scenarios.
GRB 020903 is a long-duration gamma ray burst (LGRB) with a host galaxy close enough and extended enough for spatially-resolved observations, making it one of less than a dozen GRBs where such host studies are possible. GRB 020903 lies in a galaxy host complex that appears to consist of four interacting components. Here we present the results of spatially-resolved spectroscopic observations of the GRB 020903 host. By taking observations at two different position angles we were able to obtain optical spectra (3600-9000{AA}) of multiple regions in the galaxy. We confirm redshifts for three regions of the host galaxy that match that of GRB 020903. We measure metallicity of these regions, and find that the explosion site and the nearby star-forming regions both have comparable sub-solar metallicities. We conclude that, in agreement with past spatially-resolved studies of GRBs, the GRB explosion site is representative of the host galaxy as a whole rather than localized in a metal-poor region of the galaxy.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
