Paola Focardi

• University of Bologna

We used resolved star counts from Hubble Space Telescope ( HST ) images to determine the center of gravity and the projected density profiles of six old globular clusters (GCs) in the Large Magellanic Cloud (LMC), namely NGC 1466, NGC 1841, NGC 1898, NGC 2210, NGC 2257, and Hodge 11. For each system, the LMC field contribution was properly taken in...

We used optical images acquired with the UVIS channel of the Wide Field Camera 3 on board the Hubble Space Telescope to construct the first high-resolution extinction map in the direction of NGC 6440, a globular cluster located in the bulge of our Galaxy. The map has a spatial resolution of 0.″5 over a rectangular region of about 160″ × 240″ around...

We used optical images acquired with the UVIS channel of the Wide Field Camera 3 on board of the Hubble Space Telescope to construct the first high-resolution extinction map in the direction of NGC 6440, a globular cluster located in the bulge of our Galaxy. The map has a spatial resolution of 0.5" over a rectangular region of about 160" X 240" aro...

Context. Galaxy-scale gravitational lenses are powerful tools, which can be used to address major astrophysical questions that are still open. They can be identified either through imaging or through spectroscopy, which is less efficient than imaging but offers the major advantage of having both source and deflector red shift previously measured at...

We investigate the effect of the environment on the Faber Jackson (FJ) relation, using a sample of 384 nearby elliptical galaxies and estimating objectively their environment on the typical scale of galaxy clusters. We show that the intrinsic scatter of the FJ is significantly reduced when ellipticals in high density environments are compared to el...

We have carried out a spectroscopic study to determine the frequency and nature of the nuclear activity found in compact groups. With this aim we chose two samples, one selected from the Hickson Compact Groups Catalogue and another one from the Updated Zwicky Catalogue of Compact Groups. With the analysis of 1056 galaxies we found that more than 71...

To explore the connection between AGN activity and environment in the nearby Universe, we have carried out a spectroscopic study to determine the frequency and nature of the nuclear activity in two well-defined samples of compact groups (CGs) of galaxies: Hickson Compact Groups and Updated Zwicky Catalogue of Compact Groups. We found that a large f...

After analysis of the frequency and nature of nuclear activity in two samples of Compact Groups (CGs) of Galaxies we find a remarkable deficiency of Broad Line AGNs relative to Narrow Line AGNs, despite the high frequency of active nuclei found in these groups. The cause of the deficiency may be related to the typical compact group environment. The...

In spite of careful selection of very homogeneous objects, both in terms of optical properties and environmental characteristics, we were unable to significantly reduce the large spread in the Lx vs Lb plane. We confirm that optical luminosities are not clear predictors of the X-ray luminosity in early-type galaxies, even when environmental effects...

We investigate the X-ray properties of four isolated elliptical galaxies, selected from the Updated Zwicky Catalog according to strict isolation criteria. Isolated galaxies are not influenced by the group/cluster environment, and their X-ray emission can be studied independently of the often overwhelming contribution of the hot intergalactic medium...

Based on a new survey of AGN activity in Compact Groups of Galaxies, we report a remarkable deficiency of Broad Line AGNs as compared to Narrow Line AGNs. The cause of such deficiency could be related to the average low luminosity of AGNs in CGs: $10^{39}$ erg s$^{-1}$. This result may imply lower accretion rates in CG AGNs, making Broad Line Regio...

Galaxy pairs are ideal sites in which to investigate the role of interaction on nuclear activity. For this reason we have undertaken a spectroscopic survey of a large homogeneous sample of galaxy pairs (UZC-BGP) and we present the results of the nuclear spectral classification of 48 pairs (more than half of the whole sample). The fraction of emissi...

Preliminary results of the X-ray analysis of three nearby, bright, and truly isolated Ellipticals show that even with just three objects, carefully selected to have similar optical and environmental characteristics, we can reproduce, at their L B , almost the full L X range observed for elliptical galaxies.

Compact Groups are ideal systems to study galaxy-galaxy interactions and eventually the activity-environment-morphology relationship.

Compact Groups are ideal places to investigate the role of environment on galaxy formation and evolution. Their high galaxy density coupled with their low velocity dispersion makes them the most suitable systems to study galaxy-galaxy interaction and the AGN-environment relation. UZC Compact Groups sample (UZC-CG, Focardi & Kelm 2002) contains 986...

We analyse the level of nuclear activity in galaxies belonging to UZC-CGs. Spectra are available for 868 galaxies (90% of the whole catalog); 67 % of them show nuclear activity (AGN or Star formation). To carry out a detailed study about the nuclear activity and its relationship with properties of the host galaxy and parent group we select a sample...

We present a new sample of bright galaxy pairs extracted applying an objective selection code to the UZC catalog. The sample is volume-limited to Mzw=-18.9+5logh and contains 89 galaxy pairs. We analyze the kinematical, morphological, and photometrical properties of galaxies belonging to this sample. (1 data file).

We present a new sample of bright galaxy pairs extracted applying an objective selection code to UZC catalog.The sample is volume limited to M$_{zw}$ = -18.9 +5 log ${\it h}$ and contains 89 galaxy pairs.We analyze the kinematical, morphological and photometrical properties of galaxies belonging to this sample. We show that velocity separation, $|...

The observations were performed at the ESO 3.6-m telescope in La Silla, Chile during the nights of 2000 May 5 and 6. Details of the observations and the data reduction procedures are described in Paper II (Grutzbauch et al., 2005, Cat. ). (1 data file).

We present the results of a photometric and spectroscopic study of seven members of the NGC 5328 group of galaxies, a chain of galaxies spanning over 200 kpc (H0= 70 km s−1 Mpc−1). We analyse the galaxy structure and study the emission-line properties of the group members looking for signatures of star formation and active galactic nucleus activity...

We examine the relative fractions of passive (Type 1), quiet-SF (Type 2) and active-SF (Type 3+4) galaxies as a function of luminosity and number of neighbours in several volume limited samples selected from the 2dFGRS. Neighbours are counted within 1 $h_{75}^{-1}$ Mpc projected distance, and $\pm$ 1000 km s$^{-1}$ depth. We apply a maximum magnitu...

This paper is part of a series that focuses on investigating galaxy formation and evolution in small-scale systems of galaxies in low-density environments. We present results from a study of the NGC 4756 group, which is dominated by the elliptical galaxy NGC 4756. The characteristics of the group are investigated through (1) the detailed investigat...

We present results from a study of the NGC 4756 group which is dominated by the elliptical galaxy NGC 5746. The characteristics of the group are investigated through (a) the detailed investigation of the morphological, photometric and spectroscopic properties of nine galaxies among the dominant members of the group (b) the determination of the phot...

We explore the close environment of active star-forming galaxies (ASF) in the 2dF. We find ASF galaxies to be the most likely population to inhabit extremely close pairs located in low density regions. In addition, we find that ASF galaxies in these pairs are almost entirely concentrated in the -20 < M_B < -19 magnitude range.

We use a complete AGN sample (Ho et al. 1997) to study the environment of Seyferts, LINERs and HII galaxies. For each AGN we search for companions in the UZC redshift catalogue and compute local as well as large scale neighbour density and distance to the nearest neighbour. We find that on small scale (~ 0.2 h^-1 Mpc) LINERs exhibit denser environm...

We compare the SFR of single star-forming galaxies with the SFR of star-forming galaxies in pairs. Volume-limited samples are compared selected from the 2dFGRS, applying a maximum magnitude difference criterion. We show that SF galaxies in SF + SF pairs typically increase their SFR as they get fainter, whereas this does not happen for SF galaxies i...

We investigate whether the spectral-type of a locally dominant (most luminous) galaxy can be used to select sets of galaxies that are physically associated (groups). We assume that passive dominants trace a group-like potential, and SF-dominants a field-like environment. The group sample includes 988 groups selected in the 2dFGRS applying a maximum...

A new volume-limited sample of 84 isolated pairs of galaxies has been selected from the UZC catalogue. Galaxies in pairs are brighter than $M_{Zw}-5\log h =-18.9$. The projected separation between pair members is $r < 200 h^{-1}$ kpc, the isolation criterion requires the pair to have no further companion within a $R=1 h^{-1}$ Mpc distance. Morpholo...

We present results concerning the occurrence of Seyfert galaxies in a new automatically selected sample of nearby Compact Groups of galaxies (UZC-CGs). Seventeen Seyferts are found, constituting ~3% of the UZC-CG galaxy population. CGs hosting and non-hosting a Seyfert member exhibit no significant differences, except that a relevant number of Sy2...

We examine the environment of star-forming galaxies selected in the 2dFGRS. We find that bright star-forming galaxies display a significant deficit of faint neighbours relative to passive galaxies. If a deficit in fainter companions implies a smaller mass halo, data support a scenario predicting star-formation to be suppressed in all systems more m...

The nature of Compact Groups (CGs) is investigated by comparing the luminosities and morphologies of CG galaxies, CG Neighbours and Isolated galaxies. CGs turn out to include more early type galaxies than Isolated galaxies and fewer low-luminosity galaxies. The 33 CGs with a dominant E/S0 and the 30 CGs with a dominant spiral have similar LF parame...

This paper is the first of a series addressed to the investigation of galaxy formation/evolution in small scale systems of galaxies (SSSGs) which are located in low density cosmic environments. Our algorithm for SSSG selection includes galaxy systems of 2 or more galaxies lying within 1000 km/s and a 200 h_{100}^{-1} kpc radius volume. We present t...

This is a study concerning the investigation of galaxy formation and evolution in small-scale structures and the influence of the environment on the properties of galaxies. The environment plays a key role in the evolution of galaxies since it governs the type of encounters. We present results from low-resolution spectroscopy and R-band surface pho...

IR properties of Compact Group (CG) galaxies are presented and compared with IR properties of isolated galaxies. Despite CGs displaying more E-S0s and optically bright galaxies, no differences are retrieved concerning FIR emission. The observed lack of strong FIR enhancement in the CG sample is not surprising when interpreting FIR sources in CGs as...

Isolated compact structures are investigated to identify possible links between their characteristics and the presence of an AGN.

We present results concerning the occurrence of Seyfert galaxies in a new large sample of Compact Groups (Focardi & Kelm 2002). Seyfert galaxies turn out to be relatively rare (<3%), with a significant dominance of Sy2. Seyferts are preferentially associated to Compact Groups displaying relatively high velocity dispersion and a large number of neig...

The nature of Compact Groups (CGs) is investigated by comparing the luminosities and morphologies of CG galaxies, CG Neighbours and Isolated galaxies. CGs turn out to include more early type galaxies than Isolated galaxies and fewer low-luminosity galaxies. The 33 CGs with a dominant E/S0 and the 30 CGs with a dominant spiral have similar LF parame...

Applying an automatic neighbour search algorithm to the 3D UZC galaxy catalogue (Falco et al., 1999, Cat. ) we have identified 291 compact groups (CGs) with radial velocity between 1000 and 10000km/s. The sample is analysed to investigate whether Triplets display kinematical and morphological characteristics similar to higher order CGs (Multiplets)...

Cross correlation between the ACO cluster sample and the AGN catalogue by Véron-Cetty & Véron (2000) indicates that as much as 9% of all nearby Seyfert galaxies might be physical cluster members. The fraction reduces to ≈ 3%, when membership in the central Abell radius is demanded. No differences between Sy1 and Sy2 can be retrieved concerning occu...

This is a progress report on a study concerning the role of the environment on galaxy activity ranging from star formation to AGN activity. Dense galaxy groups, where interactions are supposed to influence significantly the physical properties of the members, are therefore an ideal laboratory to study such effects. We present preliminary results on...

Environment of bright Sy1 and Sy2 galaxies has been compared applying an objective neighbour searching code on a complete galaxy sample. Sy2 exhibit an excess of companions on all investigated scales, from 50 kpc up to 1 Mpc. Sy1 with companions are lacking among less luminous sources.

Applying an automatic code to the 3D UZC galaxy catalogue, we have extracted a complete sample of about 400 physical compact groups having cz≤10000 km/s and at least 3 member galaxies within a projected distance radius of 200 h −1 kpc. We find interaction pattern to be more common among triplets than among higher multiplicity compact groups, which...

We present the results of a statistical study to search for signs of influence from nearby companions on the radio emission properties of Seyfert galaxies. We carried out our study on an optically selected sample of isolated and paired Seyferts. AGN seems to be the dominant mechanism to produce radio emission in our sample. The power distribution f...

Cross correlation between the ACO cluster sample and the AGN catalogue by Véron-Cetty & Véron (2000) indicates that as much as 9% of all nearby Seyfert galaxies might be physical cluster members. The fraction reduces to ≈ 3%, when membership in the central Abell radius is demanded. No differences between Sy1 and Sy2 can be retrieved concerning occu...

A method of searching for multiplets in a large catalogue of galaxies with measured redshifts is described. Compact Groups samples having different local and global characteristics are generated when the algorithm is applied to ZCAT catalogue. Both local and environmental galaxy density have been computed thus allowing to define truly isolated comp...

We report on a broad-band R surface photometric and low resolution spectroscopic study of a set of galaxies located in small groups and pairs of galaxies considered to be in low density environment. Groups span a wide range in density and show different morphological mix. We are analyzing systemic velocities, photometric parameters and spectral pro...

The role played by environment on nuclear activity in galaxies is not clear and largely debated (see e.g. Barnes & Hernquist 1992, Kelm 1996). To overcome statistical uncertainties, environment properties of two large samples of Seyfert galaxies (Sy 1 and Sy 2 have been kept separated) have been computed and compared with equivalent size “normal ga...

The role played by environment on nuclear activity in galaxies is not clear and largely debated (see e.g. Barnes & Hernquist 1992, Kelm 1996). To overcome statistical uncertainties, environment properties of two large samples of Seyfert galaxies (Sy 1 and Sy 2 have been kept separated) have been computed and compared with equivalent size “normal ga...

The occurrence of Seyfert galaxies in 6 samples representative of different cosmological environments (i.e. isolated pairs, compact and loose groups) is analysed. To avoid biases linked to subjective sample selection criteria only canonical samples, taken from the literature, are considered. It is found that the average frequency of Seyferts in all...

this paper, we re-examine the issue of a different kinematical behaviour for early- and late-type galaxies, by using the extensive data-base on cluster galaxies provided by the ENACS (ESO Nearby Abell Cluster Survey). As morphologies are not available for all the galaxies in our survey, we identified two galaxy populations according to the the pres...

The occurrence of Seyfert galaxies in 6 samples representative of different cosmological environments (i.e. isolated pairs, compact and loose groups) is analysed. To avoid biases linked to subjective sample selection criteria only canonical samples, taken from the literature, are considered. It is found that the average frequency of Seyferts in all...

In the framework of a a long term project aiming at the measurement of distances for an all sky sample of early-type galaxies, the authors have analysed the effects of noise and metallicity on the accuracy of velocity dispersion measurements.

Properties of Seyfert galaxies located inside groups are compared with isolated systems in order to verify whether groups are a favourable environment for nuclear activity.

We have studied the frequency of occurrence, the kinematics and the spatial distribution of Emission-Line Galaxies (ELG) in clusters in the ESO Nearby Abell Cluster Survey (ENACS). More than 90% of the ELG are spirals, but the ELG represent only 30% of all spirals. The true ELG fraction in clusters is 0.10; this is consistent with that in the field...

The Southern Sky Redshift Survey includes 13 groups of 5 or more members with velocities >=2000km/s. By measuring redshifts and accumulating data from the literature, we increase the total number of known group members from 89 to 218. We also measured new redshifts for 59 foreground/background galaxies superimposed on the group neighborhoods. The v...

We describe the results of the ESO Key-programme on "Structure and Dynamics of Rich Galaxy Clusters" (which we will henceforth refer to as the ESO Nearby Abell Cluster Survey - or ENACS). We discuss the sample of clusters for which data were obtained, and the observational programme of spectroscopy and photometry that we carried out. The final data...

The Southern Sky Redshift Survey (SSRS) includes 13 groups of 5 or more members with velocities >=2000km/s. By measuring redshifts and accumulating data from the literature, we increase the total number of known group members from 89 to 218. We also measured new redshifts for 59 foreground/background galaxies superimposed on the group neighborhoods...

The ESO Nearby Abell Cluster Survey (the ENACS) has yielded 5634 redshifts for galaxies in the directions of 107 rich, Southern clusters selected from the ACO catalogue (Abell et al. 1989). By combining these data with another 1000 redshifts from the literature, of galaxies in 37 clusters, we construct a volume-limited sample of 128 RACO>=1 cluster...

We use a set of 91 clusters observed in the course of the ESO Nearby Abell Cluster Survey (ENACS) and another 37 clusters taken from the literature in order to construct a volume-limited sample of nearby clusters (z <0.08). We define the 3-dimensional Abell richness class R3D and we evaluate the spatial density of clusters with R3D ≥1. For a subset...

Summary - By using the data from the ESO Nearby Abell Cluster Survey (ENACS), we have studied the properties of emission-line galaxies (ELG) in clusters. The fraction of ELG in clusters is 16~\%; this fraction is slightly dependent on the cluster velocity dispersion, being larger for ``colder'' systems. ELG tend to occur more frequently than other...

Summary - By combining the 5634 redshifts from the ESO Nearby Abell Cluster Survey (the ENACS) with another 1000 redshifts from the literature we are able to study the distribution of velocity dispersions for a volume-limited sample of 128 $R_{\rm ACO} \geq 1$ clusters, out to a redshift $z=0.1$, in a solid angle of 2.55 sr centered on the South Ga...

Summary - We describe the results of the ESO Key-programme on `Structure and Dynamics of Rich Galaxy Clusters' (or ENACS). The final database contains a total of 5634 galaxies in the directions of 107 clusters from the ACO catalogue with richness $R\ge 1$ and mean redshifts $z \le 0.1$. Of the 5634 redshifts, 4465 are based on absorption lines only...

We describe the first results of the observational programme of photometry and spectroscopy of the ESO Nearby Abell Cluster Survey (ENACS). The final data base contains a total of 5634 galaxies in the direction of 107 clusters with richness class R ≥ 1 and redshift z ≤0.1. Applying a velocity gap of 1000 km/s, we identify galaxy systems in the 107...

We describe the progress of the ESO key-program survey of rich nearby clusters of galaxies. We give a short description of the general properties of these clusters. First preliminary results are presented.

Our proposed method to study the star formation histories in nearby irregulars is here applied to NGC 6822. To this purpose we have obtained accurate CCD photometry of three regions in the galaxy, reaching V$\simeq$23.5 with an accuracy of $\sigma_{BVR}\leq$0.1 mag. The comparison of the observational color-magnitude diagrams and luminosity functio...

. - We present radial velocities of 53 galaxies lying in the direction of 13 southern ACO rich clusters (Abell et al 1989). The observations were carried out with the 1.5 m ESO telescope. The spectra have a wavelength range from 3800 to 6800 A with a resolution of ~12 A. For each galaxy we present accurate optical position and finding chart

Deep CCD photometry is applied to study star formation in two regions of DDO 210 and three regions of NGC 3109. Color-magnitude diagrams and luminosity functions are used to derive information on stellar populations, star formation rates, and initial mass functions of these regions in the last 1 Gyr, over which star-formation activity has been cont...

Not Available (1 data file).

Given the uncertainties in the derivation of the current and past SFR in galaxies of any kind, the SF regime in irregulars is subject of wide debate. Since the most direct information on the stellar populations and relative histories in any system can be derived from their CMD, we have undertaken a project for accurately studying the CMDs and lumin...

The paper reports 406 redshifts for galaxies in the northern galactic hemisphere, south of delta = 0 deg. A substantial fraction of the observed galaxies are located in the equatorial zone between delta values of -17.5 and 0 deg. By combining these new data with those available in the literature, it is possible to extend the original CfA redshift s...

An observational program, called a Key Program, that uses a sample of clusters of galaxies from the revised and south extended Abell catalog (Abell, Corwin and Olowin, 1989) is briefly described. The Leiden ASTROSCAN plate-measuring machine is used to scan photographic plates, i.e. glass copies of the red PSS for the northern clusters and film copi...

The present study investigates a novel method for studying the star formation histories of nearby irregular galaxies. B, V, and R CCD photometry is obtained of 2434 objects down to about 26 in two regions of the Local Group galaxy Sextans B. Substantial information on the stellar population, star formation rate, and initial mass function in the gal...

The process of star formation (SF) and the modalities with which it occurs in galaxies of different sizes are still poorly understood. On the other hand, interpretation of the chemical and photometric properties of galaxies requires the adoption of adequate laws for the SF rate and Initial Mass Function (IMF) in model computations. Dwarf irregular...

We present a study on two clusters belonging to the Centaurus concentration of galaxies, which are about 12 Mpc (H0 = 100 km s-1 Mpc-1) away from the Centaurus cluster. Photographic photometry and radial velocities have been obtained for galaxies in two square fields centered on the brightest members of each cluster. We have derived dynamical param...

The stellar population of the irregular galaxy DDO 210 has been resolved down to V = 23.5 on CCD images centered at coordinates rather different from those quoted in the literature. DDO 210 turns out to be highly contaminated by foreground stars and by background galaxies belonging to a distant cluster. The actual stellar population of this irregul...

Results are reported from dynamical study of the Eridanus group of galaxies. This system is quite prominent in one of the large-scale features found in the recently completed Southern Sky Redshift Survey (da Costa et al., 1988): the Eridanus-Fornax-Dorado filament. The irregualr aspect of Eridanus suggests the existence of subclustering, which is c...

Rich clusters of galaxies are of great interest for several reasons. As the largest bound structures that can be fairly easily found and studied in detail, they represent a formidable constraint for theories of the formation of largescale structure in the Universe. In addition, they provide an ideal laboratory for the study of the behaviour of gala...

In order to study the history of star formation in dwarf irregular galaxies we have started a project of deep CCD observations of irregulars in the Local Group. For the theoretical interpretation of the colour-magnitude diagrams resulting from these observations we present a new method of numerical simulations based on stellar evolutionary tracks....

A spectroscopic analysis based on high S-SNR high-dispersion spectra is presented for four stars suspected to be G or K supergiants lying out of the galactic plane or having peculiar high velocities. This analysis shows that three of them (HD 45829, HD 63700, and HD 68752) are likely to be normal supergiants, though closer than formerly considered;...

We present here some preliminary results and considerations regarding high resolution spectroscopy of Nova Centauri 1986. This object was discovered on November 22.7 UT as a 5.6 V magnitude star (1), and observed by us in Ha two months later, when it was of about 10 magnitude. A considerable change in the Ha line profile, basically consisting in th...

The authors are undertaking a morphological and (eventually) photometric study of a sample of emission-line galaxies from UGC. The total sample consists of 120 galaxies. For 60 objects B and R CCD images are presently obtained.

Observations made with the 1.5-m La Silla ESO telescope at a dispersion of 172 A/mm are used to obtain radial velocities for 39 galaxies in 13 rich clusters in the southern hemisphere taken from the catalog of Abell et al. (1989). For each cluster, the galaxy identification number, the right ascension and declination (1950.0 equinox), and the helio...

New redshifts obtained by means of photographic spectra at the 152 cm telescope in Loiano have allowed us to derive a sample of 189 UGC [1] galaxies with mph ≤ 14.5 and lying at RA ∈ [6h, 14h], DEC ∈ [63o,78°]. The region had been only partially covered by the Cfa Survey [2]. The sample is 84% complete.

The Perseus Supercluster is a huge structure belonging to the Southern Galactic Hemisphere and probably extending to the Northern one [1]. It has been the subject of many different studies.

Emission lines are often observed in high luminosity stars and provide evidence of the presence of extended stellar envelopes. Ha is the most frequently observed across the H-R diagram, but lines of Hel or Fell are also found in emission in these stars. They could be used as diagnostics of the structure of their outer atmospheres and winds. High re...

A qualitative description is given of spectral properties, dynamical behaviour and morphology of a selection of mainly southern radio galaxies which have been observed to have extended ionized gas in their vicinity. The question of the significance of this gas in relation to cooling flows is still very much an open one.

The design and performance parameters of the CCD camera system for the 1.5-m Loiano telescope at Bologna Observatory are listed in tables and illustrated with graphs and block diagrams. Consideration is given to the 3320 x 512-pixel CCD detector, the control and data-acquisition computer, and the overall optical efficiency of the Loiano system. Sam...

A deep image of the Kepler SNR has been obtained in the light of H-alpha + N II forbidden-line with the faint object spectrograph and camera (EFOSC) and a CCD detector at the ESO 3.6 m telescope. The visibility of the optically emitting knots of ionized gas has been greatly enhanced by subtraction of the continuum radiation. Features as faint as 2...