On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ∼ 1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40 − 8 + 8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 M ⊙ . An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ∼ 40 Mpc ) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ∼ 9 and ∼ 16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta.

We have obtained the best t to the light pro les of a luminosity limited sample of elliptical and S0 galaxies with a power law r 1=n , letting the exponent remain free rather than keeping it xed at 1=n = 1=4 as in the well known de Vaucouleurs formula. The introduction of a free parameter in the tting formula (ranging from n = 0:5 for hr e i = 0:3 kpc to n = 16 for hr e i = 25 kpc) is justi ed by the existence of a good correlation between n and the global galaxian parameters, such as total luminosity and scale-radius. This result seems to be in line with the segregation of properties between the`ordinary' and`bright' families of early-type galaxies, and has consequence for the claimed independence of the shape of galaxy pro les with respect to the Fundamental Plane parameters.

The merger of two neutron stars is predicted to give rise to three major detectable phenomena: a short burst of γ-rays, a gravitational-wave signal, and a transient optical-near-infrared source powered by the synthesis of large amounts of very heavy elements via rapid neutron capture (the r-process). Such transients, named 'macronovae' or 'kilonovae', are believed to be centres of production of rare elements such as gold and platinum. The most compelling evidence so far for a kilonova was a very faint near-infrared rebrightening in the afterglow of a short γ-ray burst at redshift z = 0.356, although findings indicating bluer events have been reported. Here we report the spectral identification and describe the physical properties of a bright kilonova associated with the gravitational-wave source GW170817 and γ-ray burst GRB 170817A associated with a galaxy at a distance of 40 megaparsecs from Earth. Using a series of spectra from ground-based observatories covering the wavelength range from the ultraviolet to the near-infrared, we find that the kilonova is characterized by rapidly expanding ejecta with spectral features similar to those predicted by current models. The ejecta is optically thick early on, with a velocity of about 0.2 times light speed, and reaches a radius of about 50 astronomical units in only 1.5 days. As the ejecta expands, broad absorption-like lines appear on the spectral continuum, indicating atomic species produced by nucleosynthesis that occurs in the post-merger fast-moving dynamical ejecta and in two slower (0.05 times light speed) wind regions. Comparison with spectral models suggests that the merger ejected 0.03 to 0.05 solar masses of material, including high-opacity lanthanides.

The kinematics of the outer parts of three intermediate-luminosity elliptical galaxies have been studied using the Planetary Nebula Spectrograph. The galaxies' velocity dispersion profiles are found to decline with radius; dynamical modeling of the data indicates the presence of little if any dark matter in these galaxies' halos. This surprising result conflicts with findings in other galaxy types, and poses a challenge to current galaxy formation theories.Over the past twenty-five years, astronomers have gone from being surprised by the existence of dark matter to the understanding that in fact most of the Universe is dominated by exotic non-luminous material. In the prevailing paradigm, the gravitational influence of "cold 1

We present new planetary nebulae (PNe) positions, radial velocities and magnitudes for six early-type galaxies obtained with the Planetary Nebulae Spectrograph (PNS), along with derived two-dimensional velocity and velocity dispersion fields, and the alpha parameters (i.e. the number of PNe per unit luminosity). We also present new deep absorption-line\ud long-slit kinematics for three galaxies in the sample, obtained with the FOcal Reducer and low dispersion Spectrograph (FORS2) at the Very Large Telescope (VLT).We extend this study to include additional 10 early-type galaxies with PNe radial velocity measurements available from the literature, including previous PNS studies, in order to obtain a broader description of the outer-halo kinematics in early-type galaxies. These\ud data extend the information derived from stellar absorption-line\ud kinematics to typically several and up to 8 effective radii.The\ud combination of photometry, absorption-line and PNe kinematics shows (i) a good agreement between the PNe number density distribution and the stellar surface brightness in the region where the two data sets overlap; (ii) a good agreement between PNe and absorption-line kinematics; (iii) that the mean rms velocity profiles fall into two groups, with part of the galaxies characterized by slowly decreasing profiles and the remainder having steeply falling profiles; (iv) a larger variety of velocity dispersion radial profiles; (v) that twists and misalignments in the velocity fields are more frequent at large radii, including some fast rotator galaxies;\ud (vi) that outer haloes are characterized by more complex radial profiles of the specific angular momentum-related lambda(R) parameter than observed within 1 R-e; (vii) that many objects are more rotationally dominated at large radii than in their central parts and (viii) that the halo kinematics are correlated with other galaxy properties, such as total B band and X-ray luminosity, isophotal shape, total stellar mass, V/sigma\ud and alpha parameter, with a clear separation between fast and slow rotators

We have started a new, deep multi-imaging survey of the Fornax cluster, dubbed the Fornax Deep Survey (FDS), at the VLT Survey Telescope (VST). In this paper we present the deep photometry inside two square degrees around the bright galaxy NGC1399 in the core of the cluster. We found that the core of the Fornax cluster is characterized by a very extended and diffuse envelope surrounding the luminous galaxy NGC1399: we map the surface brightness out to 33 arcmin (∼192 kpc) from the galaxy center and down to μ g ∼31 mag arcsec −2 in the g band. The deep photometry allows us to detect a faint stellar bridge in the intracluster region on the west side of NGC1399 and toward NGC1387. By analyzing the integrated colors of this feature, we argue that it could be due to the ongoing interaction between the two galaxies, where the outer envelope of NGC1387 on its east side is stripped away. By fitting the light profile, we found that there exists a physical break radius in the total light distribution at R=10 arcmin (∼58 kpc) that sets the transition region between the bright central galaxy and the outer exponential halo, and that the stellar halo contributes 60% of the total light of the galaxy (Section 3.5). We discuss the main implications of this work on the build-up of the stellar halo at the center of the Fornax cluster. By comparing with the numerical simulations of the stellar halo formation for the most massive bright cluster galaxies (i.e., M M 13 log 14, we find that the observed stellar halo mass fraction is consistent with a halo formed through the multiple accretion of progenitors with stellar mass in the range 10 8 -10 11 M e . This might suggest that the halo of NGC1399 has also gone through a major merging event. The absence of a significant number of luminous stellar streams and tidal tails out to 192 kpc suggests that the epoch of this strong interaction goes back to an early formation epoch. Therefore, different from the Virgo cluster, the extended stellar halo around NGC1399 is characterized by a more diffuse and well-mixed component, including the intracluster light.

Context. The Fornax Deep Survey (FDS), an imaging survey in the u , g , r , and i -bands, has a supreme resolution and image depth compared to the previous spatially complete Fornax Cluster Catalog (FCC). Our new data allows us to study the galaxies down to r -band magnitude m r ≈ 21 mag (M r ≈ −10.5 mag), which opens a new parameter regime to investigate the evolution of dwarf galaxies in the cluster environment. After the Virgo cluster, Fornax is the second nearest galaxy cluster to us, and with its different mass and evolutionary state, it provides a valuable comparison that makes it possible to understand the various evolutionary effects on galaxies and galaxy clusters. These data provide an important legacy dataset to study the Fornax cluster. Aims. We aim to present the Fornax Deep Survey (FDS) dwarf galaxy catalog, focusing on explaining the data reduction and calibrations, assessing the quality of the data, and describing the methods used for defining the cluster memberships and first order morphological classifications for the catalog objects. We also describe the main scientific questions that will be addressed based on the catalog. This catalog will also be invaluable for future follow-up studies of the Fornax cluster dwarf galaxies. Methods. As a first step we used the SExtractor fine-tuned for dwarf galaxy detection, to find galaxies from the FDS data, covering a 26 deg 2 area of the main cluster up to its virial radius, and the area around the Fornax A substructure. We made 2D-decompositions of the identified galaxies using GALFIT, measure the aperture colors, and the basic morphological parameters like concentration and residual flux fraction. We used color-magnitude, luminosity-radius and luminosity-concentration relations to separate the cluster galaxies from the background galaxies. We then divided the cluster galaxies into early-and late-type galaxies according to their morphology and gave first order morphological classifications using a combination of visual and parametric classifications. Results. Our final catalog includes 14 095 galaxies. We classify 590 galaxies as being likely Fornax cluster galaxies, of which 564 are dwarfs (M r > −18.5 mag) consisting our Fornax dwarf catalog. Of the cluster dwarfs we classify 470 as early-types, and 94 as late-type galaxies. Our final catalog reaches its 50% completeness limit at magnitude M r = −10.5 mag and surface brightness µ e,r = 26 mag arcsec −2 , which is approximately three magnitudes deeper than the FCC. Based on previous works and comparison with a spectroscopically confirmed subsample, we estimate that our final Fornax dwarf galaxy catalog has 10% contamination from the background objects.The catalogs are only at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/620/A165Article published by EDP Sciences A165, page 1 of 31 A&A 620, A165 (2018)

Abstract. -We present results of a CCD optical imaging survey of the ionized gas in 73 luminous elliptical and lenticular galaxies, selected from the RC3 catalog to represent a broad variety of X-ray, radio, infrared and kinematical properties. For each galaxy we have used broad-band R images and narrow-band images centered at the Hα and [NII] emission lines to derive the luminosity and distribution of the ionized gas. We found that a large fraction of E (72%) and SO (85%) galaxies in our sample contain ionized gas. The gas morphology appears to be rather smooth for most galaxies; however ~ 12% of the sample galaxies show a very extended filamentary structure. According to the morphology and size of the gas distribution, the galaxies have been classified into three broad groups, named small disk (SD), regular extended (RE) and filamentary structure (F). The mean diameter of the emitting region ranges between 1 and 10 kpc; the derived mass of the ionized gas ranges between 103 and 105 solar masses. A sig nificant correlation between Hα +[NII] and X-ray luminosities is found for those galaxies (27% of the sample) for which we have detected ionized gas and are also listed as X-ray sources. However, there are relatively strong X-ray emitting galaxies for which we have not detected Ha+[NII] emission and objects which show emission-lines but are not listed either in the EINSTEIN or in the ROSAT databases. The distribution of datapoint and upper limits in this diagram suggests that galaxies with warm gas are also X-ray emitters, while there are X-ray emitters without measur able Hα+[NII] emission. Similar characteristics are present in the correlation between the infrared luminosity in the 12 p m band and Lhα+ [nii]; correlations with other infrared wavelengths are weaker. A strong correlation was also found between the Ha+[NIIj luminosity and the luminosity in the B band inside the region occupied by the lineemitting gas. We use these correlations to discuss the possible mechanisms responsible for the gas ionization and excitation, analyzing in particular the role of the post-AGB stars and the thermal conduction from the X-ray halo in providing the necessary source of ionization.