Deep I-band Imaging of z=5.99 Quasar

Deep I-band imaging was carried out to search for the optical counterpart of the X-ray jet candidate near SDSS 1306+0356, reported by Schwartz (2002, astro-ph/0202190). The data suggest that the extended X-ray source may be a jet, related to a galaxy rather than to the quasar itself.Comment: 2 page letter, accepted for publication in Astronomy and Astrophysics Slight changes to the figure

United by skies, divided by language -- astronomy publishing in languages with small reader base

The mysteries of the Universe are international, the skies are not crossed by borders. However, the knowledge is transmitted by language, imposing linguistic barriers that are often difficult to break through. Bulgaria is considered as an example of a country with relatively small reader base -- it has a population of about 6.5 million (2021) and the Bulgarian language has probably $\sim$7 million speakers, if the diaspora in US, Germany and elsewhere is accounted for. The smaller-scale market, in comparison with larger non-English speaking countries, poses a number of limitation to the publishing landscape: (i) the local authors are discouraged to pen both popular and scientific astronomy books, because of the limited financial incentive; (ii) the market is heavily dominated by translations (from Russian before 1989, from English nowdays), but even those are fewer than in bigger countries, because the translation overhead costs are spread over smaller print runs. The history of the astronomy publishing in Bulgaria is summarized, with some distinct periods: pre-1944, the communist era 1944-1989, the modern times post 1989. A few notable publications are reviewed. Finally, some practices to help astronomy book publishing in languages with smaller reader bases are suggested, taking advantage of the recent technological developments.Comment: This is an extended write up of a poster presented at the European Week of Astronomy and Space Science (EAS) held in Valencia, Spain, Jun 26 -- Jul 1, 2022, Special Session 34: Diversity and Inclusion in European Astronomy (8 pages, 5 figures

Confirmation of a cluster of galaxies hidden behind the Galactic bulge using the VVV Survey

Suzaku and Chandra X-ray observations detected a new cluster of galaxies, Suzaku J1759-3450, at a redshift z=0.13. It is located behind the Milky Way, and the high Galactic dust extinction renders it nearly invisible at optical wavelengths. We attempt here to confirm the galaxy cluster with near-infrared imaging observations, and to characterize its central member galaxies. Images from the VVV survey were used to detect candidate member galaxies of Suzaku J1759-3450 within the central region of the cluster, up to 350 kpc from the X-ray peak emission. Color-magnitude and color-color diagrams and morphology criteria allowed us to select the galaxies among the numerous foreground sources. Fifteen candidate cluster members were found very close to a modeled red-sequence at the redshift of the cluster. Five members are extremely bright, and one is possibly a cD galaxy. The asymmetry in the spatial distribution of the galaxies respect to the X-ray peak emission is an indicator of that this cluster is still suffering a virialization process. Our investigation of Suzaku J1759-3450 demonstrates the potential of the VVV Survey to study the hidden population of galaxies in the Zone of Avoidance.Comment: 7 pages, 5 figures. Accepted for Publication in Astronomy & Astrophysic

Spectroscopy of Young Planetary Mass Candidates with Disks

It is now well established that many young brown dwarfs exhibit characteristics similar to classical T Tauri stars, including infrared excess from disks and emission lines related to accretion. Whether the same holds true for even lower mass objects, namely those near and below the Deuterium-burning limit, is an important question. Here we present optical spectra of six isolated planetary mass candidates in Chamaeleon II, Lupus I and Ophiuchus star-forming regions, recently identified by Allers and collaborators to harbor substantial mid-infrared excesses. Our spectra, from ESO's Very Large Telescope and New Technology Telescope, show that four of the targets have spectral types in the ~M9-L1 range, and three of those also exhibit H_alpha. Their luminosities are consistent with masses of ~5-15 M_{Jupiter} according to models of Chabrier, Baraffe and co-workers, thus placing these four objects among the lowest mass brown dwarfs known to be surrounded by circum-sub-stellar disks. Our findings bolster the idea that free-floating planetary mass objects could have infancies remarkably similar to those of Sun-like stars and suggest the intriguing possibility of planet formation around primaries whose masses are comparable to those of extra-solar giant planets. Another target appears to be a brown dwarf (~M8) with prominent H_alpha emission, possibly arising from accretion. The sixth candidate is likely a background source, underlining the need for spectroscopic confirmation.Comment: to appear in The Astrophysical Journal Letter

The structure and dynamics of the AC114 galaxy cluster revisited

We present a dynamical analysis of the galaxy cluster AC114 based on a catalogue of 524 velocities. Of these, 169 (32%) are newly obtained at ESO (Chile) with the VLT and the VIMOS spectrograph. Data on individual galaxies are presented and the accuracy of the measured velocities is discussed. Dynamical properties of the cluster are derived. We obtain an improved mean redshift value z= 0.31665 +/- 0.0008 and velocity dispersion \sigma= 1893+73-82 \kms. A large velocity dispersion within the core radius and the shape of the infall pattern suggests that this part of the cluster is in a radial phase of relaxation with a very elongated radial filament spanning 12000 \kms. A radial foreground structure is detected within the central 0.5/h Mpc radius, recognizable as a redshift group at the same central redshift value. We analyze the color distribution for this archetype Butcher-Oemler galaxy cluster and identify the separate red and blue galaxy sequences. The latter subset contains 44% of confirmed members of the cluster, reaching magnitudes as faint as R_{f}= 21.1 (1.0 magnitude fainter than previous studies). We derive a mass M_{200}= (4.3 \pm 0.7) x 10^15 Msun/h. In a subsequent paper we will utilize the spectral data presented here to explore the mass-metallicity relation for this intermediate redshift cluster.Comment: 17 pages, 11 figures, 4 tables, accepted for publication in MNRA