The AMIGA sample of isolated galaxies. IV. A catalogue of neighbours around isolated galaxies

Studies of the effects of environment on galaxy properties and evolution require well defined control samples. Such isolated galaxy samples have up to now been small or poorly defined. The AMIGA project (Analysis of the interstellar Medium of Isolated GAlaxies) represents an attempt to define a statistically useful sample of the most isolated galaxies in the local (z < 0.05) Universe. A suitable large sample for the AMIGA project already exists, the Catalogue of Isolated Galaxies (CIG, Karachentseva 1973; 1050 galaxies), and we use this sample as a starting point to refine and perform a better quantification of its isolation properties. Digitised POSS-I E images were analysed out to a minimum projected radius R > 0.5 Mpc around 950 CIG galaxies (those within Vr = 1500 km s-1 were excluded). We identified all galaxy candidates in each field brighter than B = 17.5 with a high degree of confidence using the LMORPHO software. We generated a catalogue of approximately 54 000 potential neighbours (redshifts exist for 30% of this sample). Six hundred sixty-six galaxies pass and two hundred eighty-four fail the original CIG isolation criterion. The available redshift data confirm that our catalogue involves a largely background population rather than physically associated neighbours. We find that the exclusion of neighbours within a factor of four in size around each CIG galaxy, employed in the original isolation criterion, corresponds to Delta Vr ~ 18000 km s-1 indicating that it was a conservative limit. Galaxies in the CIG have been found to show different degrees of isolation. We conclude that a quantitative measure of this is mandatory. It will be the subject of future work based on the catalogue of neighbours obtained here.Comment: Accepted by A&A, 10 pages, 8 figures, 4 table

Sensitive VLBI Continuum and H I Absorption Observations of NGC 7674: First Scientific Observations with the Combined Array VLBA, VLA & Arecibo

We present phase-referenced VLBI observations of the radio continuum emission from, and the H I 21 cm absorption toward, the Luminous Infrared Galaxy NGC 7674. The observations were carried out at 1380 MHz using the VLBA, the phased VLA, and theArecibo radio telescope. These observations constitute the first scientific use of the Arecibo telescope in a VLBI observation with the VLBA. The high- and low-resolution radio continuum images reveal several new continuum structures in the nuclear region of this galaxy. At ~100 mas resolution, we distinguish six continuum structures extending over 1.4 arcsec, with a total flux density of 138 mJy. Only three of these structures were known previously. All these structures seem to be related to AGN activity. At the full resolution of the array, we only detect two of the six continuum structures. Both are composed of several compact components with brightness temperatures on the order of $10^{7}$ K. While it is possible that one of these compact structures could host an AGN, they could also be shock-like features formed by the interaction of the jet with compact interstellar clouds in the nuclear region of this galaxy. Complex H I absorption is detected with our VLBI array at both high and low angular resolution. Assuming that the widest H I feature is associated with a rotating H I disk or torus feeding a central AGN, we estimate an enclosed dynamical mass of ~7 x 10^7 M_sun, comparable to the value derived from the hidden broad H$\beta$ emission in this galaxy. The narrower H I lines could represent clumpy neutral hydrogen structures in the H I torus. The detection of H I absorption toward some of the continuum components, and its absence toward others, suggest an inclined H I disk or torus in the central region of NGC 7674.Comment: 37 pages, 11 figures. ApJ accepted. To appear in the Nov. 10, 2003 issue of ApJ. Please use the PDF version if the postscript doesn't show the figure

The AMIGA sample of isolated galaxies. V. Quantification of the isolation

The AMIGA project aims to build a well defined and statistically significant reference sample of isolated galaxies in order to estimate the environmental effects on the formation and evolution of galaxies. The goal of this paper is to provide a measure of the environment of the isolated galaxies in the AMIGA sample, quantifying the influence of the candidate neighbours identified in our previous work and their potential effects on the evolution of the primary galaxies. Here we provide a quantification of the isolation degree of the galaxies in this sample. Our starting sample is the Catalogue of Isolated Galaxies (CIG). We used two parameters to estimate the influence exerted by the neighbour galaxies on the CIG galaxy: the local number density of neighbour galaxies and the tidal strength affecting the CIG galaxy. We show that both parameters together provide a comprehensive picture of the environment. For comparison, those parameters have also been derived for galaxies in denser environments such as triplets, groups and clusters. The CIG galaxies show a continuous spectrum of isolation, as quantified by the two parameters, from very isolated to interacting. The fraction of CIG galaxies whose properties are expected to be influenced by the environment is however low (159 out of 950 galaxies). The isolated parameters derived for the comparsion samples gave higher values than for the CIG and we found clear differences for the average values of the 4 samples considered, proving the sensitivity of these parameters. The environment of the galaxies in the CIG has been characterised, using two complementary parameters quantifying the isolation degree, the local number density of the neighbour galaxies and the tidal forces affecting the isolated galaxies. (Abridged)Comment: 10 pages, 12 figures, proposed for acceptance A&

Circumnuclear stellar population, morphology and environment of Seyfert 2 galaxies: an evolutionary scenario

We investigate the relation between the characteristics of the circumnuclear stellar population and both the galaxy morphology and the presence of close companions for a sample of 35 Seyfert 2 nuclei. Fifteen galaxies present unambiguous signatures of recent episodes of star formation within $\approx$300 pc from the nucleus. When we relate this property with the Hubble type of the host galaxy, we find that the incidence of recent circumnuclear star formation increases along the Hubble sequence, and seems to be larger than in non-Seyfert galaxies for the early Hubble types S0 and Sa, but similar to that in non-Seyfert galaxies for later Hubble types. Both in early-type and late-type Seyferts, the presence of recent star-formation is related to the galaxy morphology in the inner few kiloparsecs, as observed in HST images through the filter F606W by Malkan et al., who has assigned a late ``inner Hubble type'' to most Seyfert 2s with recent nuclear star-formation. This new classification is due to the presence of dust lanes and spiral structures in the inner region. The presence of recent star formation in Seyfert 2 nuclei is also related to interactions: among the 13 galaxies of the sample with close companions or in mergers, 9 have recent star formation in the nucleus. These correlations between the presence of companions, inner morphology and the incidence of recent star formation suggest an evolutionary scenario in which the interaction is responsible for sending gas inwards which both feeds the AGN and triggers star-formation. The starburst then fades with time and the composite Seyfert 2 + Starburst nucleus evolves to a ``pure'' Seyfert 2 nucleus with an old stellar population.Comment: 12 pages, 6 figures, 2 table

HI Observations of the Stephan's Quintet

Using the VLA, we have made spectral-line and continuum observations of the neutral hydrogen in the direction of the compact group of galaxies Stephan's Quintet. The high-velocity clouds between 5600 and 6600 km/s, the disk of the foreground galaxy, NGC 7320, at 800 km/s, the extended continuum ridge near the center of the group, and 3 faint dwarf-like galaxies in the surrounding field were imaged with C, CS, and D arrays. Four of the HI clouds previously detected are confirmed. The two largest HI features are coincident with and concentrated mainly along separate large tidal tails that extend eastward. The most diffuse of the four clouds is resolved into two clumps, one coincide with tidal features south of NGC 7318a and the other devoid of any detectable stellar or Halfa sources. The two compact clouds, along the same line of sight, have peak emission at luminous infrared and bright Halfa sources probably indicative of star-forming activity. The total amount of HI detected at high redshifts is ~ 10**10Msol. As in previous HI studies of the group, no detectable emission was measured at the positions of any high-redshift galaxies so that any HI still bound to their disks must be less than 2.4 x 10**7Msol.Comment: Accepted for publication in AJ and tentatively scheduled for the May 2002 issue. High-resolution ps figures are available at: http://www.iaa.es/~lourdes/bw/bw-paper.tar.g

Electrochromic and electrofluorochromic properties of a new boron dipyrromethene–ferrocene conjugate

A new boron dipyrromethene–ferrocene (BODIPY–Fc) conjugate with pentafluorophenyl as the meso substituent and two Fc termini was synthesized and its spectroscopic and electrochemical features were analyzed. An intramolecular charge transfer from the donor Fc to the acceptor BODIPY has been predicted by theory and confirmed experimentally, leading to efficient fluorescence quenching when the dyad is in the neutral state. Fluorescence can be triggered by oxidizing both ferrocenyl units either chemically or electrochemically. Eventually, a fully reversible fluorescence switch is evidenced by coupling TIRF microscopy with electrolysis in an electrochemical cell

Is natural orifice specimen extraction surgery really safe in radical surgery for colorectal cancer?

Scop: Chirurgia rectală robotică este în prezent o procedură nouă pentru cancerele rectale. Extracția eșantionului cu orificiu natural transanal (NOSE) este o tehnică nouă de îndepărtare a specimenului din cavitatea abdominală prin anus, în loc de o incizie suplimentară după o intervenție chirurgicală colorectală laparoscopică sau robotică. Siguranța NOSE rămâne controversată. Acest studiu și-a propus să investigheze siguranța precoce a NOSE transanal în tratamentul cancerului de colon sigmoid și rectal superior din următoarele aspecte: caracteristici clinice și patologice, indicatori inflamatori și imunitari și complicații postoperatorii. Prezentare de caz: O femeie de 61 de ani, diagnosticată anterior cu cancer rectal, cu antecedente de 6 luni de hematochezie și alternanta diaree-constipatie. Diagnosticul de cancer rectal a fost pus pe baza biopsiei colonoscopice care a confirmat un nodul circumferenţial neregulat de adenocarcinom bine diferenţiat la 10 cm de marginea anală. Rezecția anterioară joasă asistata robotic, urmata de extracția specimenului transanal a fost efectuată după obținerea consimțământului informat. Procedura a fost efectuată cu succes și pacienta a avut o evolutie postoperatorie fără complicații. Diagnosticul patologic postoperator a evidențiat un adenocarcinom moderat diferențiat de 4x4x0,6 cm3 și margine circumferențiala libera. Concluzii: Rezectia de rect robotica plus extractia transanala a specimenului pentru cancerul rectal poate fi efectuata în siguranță și poate fi o abordare eficientă în contrast cu abordarea deschisă sau laparoscopică.Background: Robotic rectal surgery is currently a novel procedure for rectal cancers. Transanal natural orifice specimen extraction (NOSE) is a novel technique to remove the specimen from the abdominal cavity through the anus instead of an additional incision following laparoscopic or robotic colorectal surgery. The safety of NOSE remains controversial. This study aimed to investigate the early safety of transanal NOSE in the treatment of sigmoid colon and upper rectal cancer from the follow aspects: clinical and pathological characteristics, inflammatory and immune indicators and postoperative complications. Case presentation: A 61-year-old women, previously diagnosed with rectal cancer with came 6 months history of hematochezia and altered bowel habit. A diagnosis of rectal cancer was made in view of colonoscopic biopsy which confirmed an irregular circumferential lump of well differentiated adenocarcinoma at 10 cm from the anal verge. Robotic low anterior resection (LAR) plus transanal natural orifice specimen extraction (NOSE) was performed after obtaining informed consent. The procedure was performed successfully and the patient convalesced nicely without any complications. The postoperative pathological diagnosis revealed a 4x4x0.6 cm3 moderately differentiated adenocarcinoma and circumferential clearance. Conclusions: Robotic LAR plus transanal NOSE for rectal cancer can be performed safely and may be an effective approach in contrast to open or laparoscopic approach

AMIGA project: Quantification of the isolation of 950 CIG galaxies

The role of the environment on galaxy evolution is still not fully understood. In order to quantify and set limits on the role of nurture one must identify and study a sample of isolated galaxies. The AMIGA project "Analysis of the Interstellar Medium of Isolated GAlaxies" is doing a multi-wavelength study of a large sample of isolated galaxies in order to examine their interstellar medium and star formation activity. We processed data for 950 galaxies from the Catalogue of Isolated Galaxies (CIG, Karachentseva 1973) and evaluated their isolation using an automated star-galaxy classification procedure (down to M_B ~17.5) on large digitised POSS-I fields surrounding each isolated galaxy (within a projected radius of at least 0.5 Mpc). We defined, compared and discussed various criteria to quantify the degree of isolation for these galaxies: e.g. Karachentseva's revised criterion, local surface density computations, estimation of the external tidal force affecting each isolated galaxy. We found galaxies violating Karachentseva's original criterion, and we defined various subsamples of galaxies according to their degree of isolation. Additionally, we sought for the redshifts of the primary and companion galaxies to access the radial dimension. We also applied our pipeline to triplets, compact groups and clusters and interpret the isolated galaxy population in light of these control samples.Comment: 4 pages, proceedings of the contributed talk given at the conference "Galaxies in Isolation: Exploring Nature vs. Nurture" held in Granada, May 12-15, 200