Ken-Ichi Wakamatsu

The 6dF Galaxy Survey: final redshift release (DR3) and southern large-scale structures

We report the final redshift release of the 6dF Galaxy Survey (6dFGS), a combined redshift and peculiar velocity survey over the southern sky (|b| > 10°). Its 136 304 spectra have yielded 110 256 new extragalactic redshifts and a new catalogue of 125 071 galaxies making near-complete samples with (K, H, J, r_F, b_J) ≤ (12.65, 12.95, 13.75, 15.60, 16.75). The median redshift of the survey is 0.053. Survey data, including images, spectra, photometry and redshifts, are available through an online data base. We describe changes to the information in the data base since earlier interim data releases. Future releases will include velocity dispersions, distances and peculiar velocities for the brightest early-type galaxies, comprising about 10 per cent of the sample. Here we provide redshift maps of the southern local Universe with z ≤ 0.1, showing nearby large-scale structures in hitherto unseen detail. A number of regions known previously to have a paucity of galaxies are confirmed as significantly underdense regions. The URL of the 6dFGS data base is http://www-wfau.roe.ac.uk/6dFGS.

The 6dF Galaxy Survey: samples, observational techniques and the first data release

The 6dF Galaxy Survey (6dFGS) aims to measure the redshifts of around 150 000 galaxies, and the peculiar velocities of a 15 000-member subsample, over almost the entire southern sky. When complete, it will be the largest redshift survey of the nearby Universe, reaching out to about z similar to 0.15, and more than an order of magnitude larger than any peculiar velocity survey to date. The targets are all galaxies brighter than K-tot = 12.75 in the 2MASS Extended Source Catalog (XSC), supplemented by 2MASS and SuperCOSMOS galaxies that complete the sample to limits of (H, J, r(F), b(J)) = (13.05, 13.75, 15.6, 16.75). Central to the survey is the Six-Degree Field (6dF) multifibre spectrograph, an instrument able to record 150 simultaneous spectra over the 5.7-field of the UK Schmidt Telescope. An adaptive tiling algorithm has been employed to ensure around 95 per cent fibring completeness over the 17 046 deg(2) of the southern sky with \b\ > 10degrees. Spectra are obtained in two observations using separate V and R gratings, that together give R similar to 1000 over at least 4000-7500 Angstrom and signal-to-noise ratio similar to10 per pixel. Redshift measurements are obtained semi-automatically, and are assigned a quality value based on visual inspection. The 6dFGS data base is available at http://www-wfau.roe.ac.uk/6dFGS/, with public data releases occurring after the completion of each third of the survey.

Flaring up of the compact cloud G2 during the close encounter with Sgr A

A compact gas cloud G2 (Gillessen+2012) is predicted to reach the pericentre of its orbit around the super massive black hole (SMBH) of our galaxy, Sagittarius (Sgr A*), by summer 2013. This event will give us a rare opportunity to observe the interaction between SMBH and gas around it. We report the result of the fully three-dimensional simulation of the evolution of G2 during the first pericentre passage. The strong tidal force by the SMBH stretches the cloud along its orbit, and compress it strongly in the vertical direction, resulting in the heating up and flaring up of the cloud. The bolometric luminosity will reach the maximum of 100

Japanese VLBI Network Observations of Radio-Loud Narrow-Line Seyfert 1 Galaxies

L_{\odot}

A deep 6.7 μm survey in the SSA13 field with ISO

by July 2013. This flare should be easily observed in the near infrared.

ISO deep far-infrared survey in the lockman hole: III. Catalogs and source counts at 90 & 170 μm

We performed phase-reference very long baseline interferometry (VLBI) observations on five radio-loud narrow-line Seyfert 1 galaxies (NLS1s) at 8.4 GHz with the Japanese VLBI Network. Each of the five targets (RXS J08066+7248, RXS J16290+4007, RXS J16333+4718, RXS J16446+2619, and B3 1702+457) in milli-Jansky levels were detected and unresolved in milli-arcsecond resolutions, i.e., with brightness temperatures higher than 10 7 K. The nonthermal processes of active galactic nucleus activity, rather than starbursts, are predominantly responsible for the radio emissions from these NLS1s. Out of the nine known radio-loud NLS1s, including those chosen for this study, we found that the four most radio-loud objects exclusively have inverted spectra. This suggests a possibility that these NLS1s are radio-loud due to Doppler beaming, which can apparently enhance both the radio power and the spectral frequency.

VLBI Detections of Parsec-Scale Nonthermal Jets in Radio-Loud Broad Absorption Line Quasars

We present results of a deep mid-infrared survey in the SSA13 field with the Infrared Space Observatory (ISO). In order to probe the near-infrared light at high redshifts, we surveyed the field with the broad band LW2 (5-8.5 µm) filter of the mid-infrared camera ISOCAM. Adopting a highly redundant imaging strategy for the 23 h observation and carefully treating gradual changes in the detector responsivity caused by a very high rate of cosmic ray impacts, we succeeded in reaching an 80% completeness limit of 16 µJy in the central 7 arcmin 2 region. Utilizing the signal-to-noise ratio map, we detected 65 sources down to 6 µJy in the 16 arcmin 2 field. Integral galaxy number counts at 6.7 µm are then derived, reaching 1.3 × 10 4 deg −2 at the faint limit with a slope of −1.6 between 13 µJy and 130 µJy. Integrating individual sources in this flux range, the resolved fraction of the extragalactic background light at 6.7 µm is estimated to be 0.56 nW m −2 sr −1 . These results, which reach a flux limit three times fainter than those in the Hubble Deep Fields, are in fairly good agreement with a model prediction by Franceschini et al. (1997). Finally, we discuss the relation of distant massive E/S0 galaxies to the faint 6.7 µm galaxy population.

On the nature of Hoag-type galaxy NGC 6028 and related objects

We present the catalogs and source counts for the C 90 (reference wavelength of 90m) and C 160 (170m) bands, which were extracted from our analysis of an ISO deep far-infrared survey conducted as part of the Japan/UH ISO cosmology project. The total survey area is0: 9d eg 2 in two fields within the Lockman Hole. The analysis consists of source extraction using the IRAF DAOPHOT package and simulations carried out by adding artificial sources to the maps to estimate the detection rate, the flux bias, the positional accuracy, and the noise. The flux calibration was performed using the Sb galaxy UGC 06009 - the photometric error was estimated to be50% at C 90 and65% at C 160. The total noise estimated from the simulation is dominated by the confusion noise due to the high source density. The confusion noise is 20 mJy at C 90 and35 mJy at C 160, which is much larger than the instrumental noise which is at the level of a few mJy or less. The catalogs were constructed by selecting 223 C 90 sources and 72 C 160 sources with a Signal to Noise Ratio ( SN R )o f three or greater. The distribution of the observed associations between C 90 and C 160 sources indicates that the 1 positional errors are20 00 and35 00 at C 90 and C 160, respectively. The corrections for the detection rate and the flux bias are significant for sources fainter than 200 mJy at C 90 and 250 mJy at C 160. Most of the sources detected both at C 90 and C 160 have a F(C 160)/F(C 90) color redder than the Sb galaxy UGC 06009. Such a red color could result from reddening due to the flux bias or a K-correction brightening due to the eect of redshift. Red sources brighter than 200 mJy at C 160 may be very luminous galaxies like Arp 220 at moderate redshift. The source counts are derived by applying the corrections for the detection rate and flux bias. The resultant counts are quite consistent with the constraints derived from the fluctuation analysis performed in Paper II. The C 160 counts are also consistent with the results from the FIRBACK project. Our C 90 survey, which is 2- 3 times deeper than those previously published, reveals an upturn in the count slope at around 200 mJy. While recent models give a reasonable fit to the C 160 counts, none of them are successful in accounting for the upturn in the C 90 counts. If the upturn is caused by ultraluminous IR galaxies, their redshifts would need to be at z 0:5, implying a major event in galaxy evolution at moderate redshift.

Multi-epoch VLBA observations of 3C 66A

We conducted radio detection observations at 8.4 GHz for 22 radio-loud broad absorption line (BAL) quasars, selected from the Sloan Digital Sky Survey (SDSS) Third Data Release, by a very-long-baseline interferometry (VLBI) technique. The VLBI instrument we used was developed by the Optically ConnecTed Array for VLBI Exploration project (OCTAVE), which is operated as a subarray of the Japanese VLBI Network (JVN). We aimed at selecting BAL quasars with nonthermal jets suitable for measuring their orientation angles and ages by subsequent detailed VLBI imaging studies to evaluate two controversial issues of whether BAL quasars are viewed nearly edge-on, and of whether BAL quasars are in a short-lived evolutionary phase of quasar population. We detected 20 out of 22 sources using the OCTAVE baselines, implying brightness temperatures greater than 10^5 K, which presumably come from nonthermal jets. Hence, BAL outflows and nonthermal jets can be generated simultaneously in these central engines. We also found four inverted-spectrum sources, which are interpreted as Doppler-beamed, pole-on-viewed relativistic jet sources or young radio sources: single edge-on geometry cannot describe all BAL quasars. We discuss the implications of the OCTAVE observations for investigations for the orientation and evolutionary stage of BAL quasars.

A Seyfert nucleus of a new ring galaxy in Sextans

Surface photometry has been done on the nearest and brightest Hoag-type galaxy, NGC 6028, which is known to be a peculiar galaxy consisting of a luminous core surrounded by a faint, apparently detached ring. Most of the Hoag-type galaxies are found to have oval-shaped cores, and it is suggested that the outer rings of both NGC 6028 and Hoag-type galaxies may be formed through mechanisms related to the oval structures of the central cores. A countereffect of the ring formation relating to a possible dissolution of barred structures is discussed briefly. The accretion hypothesis for the origin of outer rings is considered, and possible interactions between the accreting gas and the hot, X-ray emitting gas around elliptical galaxies are discussed. 60 refs.