The Abell 85 BCG: a nucleated, core-less galaxy

New high-resolution r band imaging of the brightest cluster galaxy (BCG) in Abell 85 (Holm 15A) was obtained using the Gemini Multi Object Spectrograph. These data were taken with the aim of deriving an accurate surface brightness profile of the BCG of Abell 85, in particular its central region. The new Gemini data show clear evidence of a previously unreported nuclear emission that is evident as a distinct light excess in the central kiloparsec of the surface brightness profile. We find that the light profile is never flat nor does it present a downward trend towards the center of the galaxy. That is, the new Gemini data show a different physical reality from the featureless, "evacuated core" recently claimed for the Abell 85 BCG. After trying different models, we find that the surface brightness profile of the BCG of Abell 85 is best fit by a double Sersic model.Comment: Gemini web feature: Supermassive black hole that wasn't - http://gemini.edu/node/1247

AGN Jets and a Fanciful Trio of Black Holes in the Abell 85 Brightest Cluster Galaxy

A new radio map of the Abell 85 Brightest Cluster Galaxy (BCG) was obtained with the Karl G. Jansky Very Large Array. With a resolution of 002, this radio image shows two kiloparsec-scale bipolar active galactic nucleus jets emanating from the active galactic nucleus of the A85 BCG. The galaxy core appears as a single entity on the new radio map. It has been assumed that the A85 BCG contained a binary black hole in its core. However, Chandra X-ray data and the new high-resolution radio map show no evidence that the A85 BCG harbors a binary black hole. The assumption that this galaxy contains a binary black hole was based on the analysis of its optical surface brightness profile obtained under poor seeing conditions. We demonstrate how the well-known blurring effects of atmospheric seeing can mimic the effects of a binary supermassive black hole (SMBH). Likewise, SDSS J004150.75–091824.3 was postulated to be a third SMBH associated with the BCG. In the optical and X-rays, SDSS J004150.75–091824.3 is a point-like source located ~14\u27\u27 away from the nucleus of the A85 BCG. A new spectrum of SDSS J004150.75–091824.3, obtained with the 10.4 m Gran Telescopio Canarias, reveals that this source is a background quasar at a redshift of z = 1.5603 ± 0.003 and not associated in any way with the A85 cluster

Which countries are leading high-impact science in astronomy?

Recent news reports claim that China is overtaking the United States and all other countries in scientific productivity and scientific impact. A straightforward analysis of high-impact papers in astronomy reveals that this is not true in our field. In fact, the United States continues to host, by a large margin, the authors that lead high-impact papers. Moreover, this analysis shows that 90% of all high-impact papers in astronomy are led by authors based in North America and Europe. That is, only about 10% of countries in the world host astronomers that publish “astronomy’s greatest hits

Monitoring of the radio galaxy M 87 during a low-emission state from 2012 to 2015 with MAGIC

M87 is one of the closest (z = 0.004 36) extragalactic sources emitting at very high energies (VHE, E \u3e 100 GeV). The aim of this work is to locate the region of the VHE gamma-ray emission and to describe the observed broad-band spectral energy distribution (SED) during the low VHE gamma-ray state. The data fromM87 collected between 2012 and 2015 as part of aMAGIC monitoring programme are analysed and combined with multiwavelength data from Fermi-LAT, Chandra, HST, EVN, VLBA, and the Liverpool Telescope. The averaged VHE gamma-ray spectrum can be fitted from ∼100 GeV to ∼10 TeV with a simple power law with a photon index of (−2.41 ± 0.07), while the integral flux above 300 GeV is (1.44 ± 0.13) × 10−12 cm−2 s−1. During the campaign between 2012 and 2015, M87 is generally found in a low-emission state at all observed wavelengths. The VHE gamma-ray flux from the present 2012–2015M 87 campaign is consistent with a constant flux with some hint of variability (∼ 3 σ) on a daily time-scale in 2013. The low-state gamma-ray emission likely originates from the same region as the flare-state emission. Given the broad-band SED, both a leptonic synchrotron self-Compton and a hybrid photohadronic model reproduce the available data well, even if the latter is preferred. We note, however, that the energy stored in the magnetic field in the leptonic scenario is very low, suggesting a matter-dominated emission region

3C 17: The BCG of a Galaxy Cluster at z = 0.22

Gemini Multi Object Spectrograph medium-resolution spectra and photometric data of 39 objects in the field of the radio galaxy 3C 17 are presented. Based on the new data, a previously uncataloged cluster of galaxies is identified at a mean redshift of z = 0.220 ± 0.003, a projected virial radius of 0.37 Mpc, and a velocity dispersion of σ v = 821 ± 171 km s-1. The brightest member of this cluster is 3C 17, with M r = -22.45 mag. The surface brightness profile of 3C 17 is best fit with two components (Exponential + Sérsic) characteristic of brightest cluster galaxies. The spectrum of 3C 17 is dominated by broad emission lines Hα + N[ ii] and Hβ + [O iii]. Analysis of Chandra data shows extended emission around the cluster core that supports the existence of hot gas cospatial with 3C 17. The discovery of a cluster of galaxies around 3C 17 better explains the sharply bent morphology of the radio jet given that it propagates through a dense intracluster medium.Fil: Madrid, Juan P.. Commonwealth Scientific And Industrial Research Organization; AustraliaFil: Donzelli, Carlos Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Rodríguez-Ardila, Alberto. Laboratorio Nacional de Astrofisica; Brasil. Instituto Astrofisico de Canarias; EspañaFil: Paggi, Alessandro. Istituto Nazionale di Astrofisica; ItaliaFil: Massaro, Francesco. Istituto Nazionale di Astrofisica; ItaliaFil: Schirmer, Mischa. Gemini Observatorysouthern Operations Center; Chile. Max Planck Institute For Astronomy; Alemani

Hubble Space Telescope Near-Infrared Snapshot Survey of 3CR Radio Source Counterparts at Low Redshift

We present newly acquired images of the near-infrared counterpart of 3CR radio sources. All the sources were selected to have a redshift of less than 0.3 to allow us to obtain the highest spatial resolution. The observations were carried out as a snapshot program using the Near-Infrared Camera and Multiobject Spectrograph (NICMOS) on-board the Hubble Space Telescope (HST). In this paper we describe 69 radio galaxies observed for the first time with NICMOS during HST cycle 13. All the objects presented here are elliptical galaxies. However, each of them has unique characteristics such as close companions, dust lanes, unresolved nuclei, arc-like features, globular clusters and jets clearly visible from the images or with basic galaxy subtraction

Structural Parameters of the M87 Globular Clusters

We derive structural parameters for ~2000 globular clusters in the giant Virgo elliptical M87 using extremely deep Hubble Space Telescope images in F606W (V) and F814W (I) taken with the ACS/WFC. The cluster scale sizes (half-light radii r_h) and ellipticities are determined from PSF-convolved King-model profile fitting. We find that the r_h distribution closely resembles the inner Milky Way clusters, peaking at r_h~2.5 pc and with virtually no clusters more compact than r_h ~ 1 pc. The metal-poor clusters have on average an r_h 24% larger than the metal-rich ones. The cluster scale size shows a gradual and noticeable increase with galactocentric distance. Clusters are very slightly larger in the bluer waveband V a possible hint that we may be beginning to see the effects of mass segregation within the clusters. We also derived a color magnitude diagram for the M87 globular cluster system which show a striking bimodal distribution.Comment: ApJ accepte