arXiv subjects

M. Moles

Publications and source records attributed to M. Moles.

157 records · Page 9Linked to original sources

arXiv2002

The WINGS Survey: a progress report

A two-band (B and V) wide-field imaging survey of a complete, all-sky X-ray selected sample of 78 clusters in the redshift range z=0.04-0.07 is presented. The aim of this survey is to provide the astronomical community with a complete set of homogeneous, CCD-based surface photometry and morphological data of nearby cluster galaxies located within 1.5 Mpc from the cluster center. The data collection has been completed in seven observing runs at the INT and ESO-2.2m telescopes. For each cluster, photometric data of about 2500 galaxies (down to V~23) and detailed morphological information of about 600 galaxies (down to V~21) are obtained by using specially designed automatic tools. As a natural follow up of the photometric survey, we also illustrate a long term spectroscopic program we are carrying out with the WHT-WYFFOS and AAT-2dF multifiber spectrographs. Star formation rates and histories, as well as metallicity estimates will be derived for about 350 galaxies per cluster from the line indices and equivalent widths measurements, allowing us to explore the link between the spectral properties and the morphological evolution in high- to low-density environments, and across a wide range in cluster X-ray luminosities and optical properties.

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arXiv2002

Rotation curves and metallicity gradients from HII regions in spiral galaxies

In this paper we study long slit spectra in the region of H$α$ emission line of a sample of 111 spiral galaxies with recognizable and well defined spiral morphology and with a well determined environmental status, ranging from isolation to non-disruptive interaction with satellites or companions. The form and properties of the rotation curves are considered as a function of the isolation degree, morphological type and luminosity. The line ratios are used to estimate the metallicity of all the detected HII regions, thus producing a composite metallicity profile for different types of spirals. We have found that isolated galaxies tend to be of later types and lower luminosity than the interacting galaxies. The outer parts of the rotation curves of isolated galaxies tend to be flatter than in interacting galaxies, but they show similar relations between global parameters. The scatter of the Tully-Fisher relation defined by isolated galaxies is significantly lower than that of interacting galaxies. The [NII]/H$α$ ratios, used as metallicity indicator, show a clear trend between Z and morphological type, t, with earlier spirals showing larger ratios; this trend is tighter when instead of t the gradient of the inner rotation curve, G, is used; no trend is found with the interaction status. The Z-gradient of the disks depends on the type, being almost flat for early spirals, and increasing for later types. The [NII]/H$α$ ratios measured for disk HII regions of interacting galaxies are higher than for normal/isolated objects, even if all the galaxy families present similar distributions of H$α$ Equivalent Width.

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arXiv2002

The scaling relations of early--type galaxies in clusters I. Surface photometry in seven nearby clusters

This is the first paper of a series investigating the scaling relations of early-type galaxies in clusters. Here we illustrate the multi-band imagery and the image reduction and calibration procedures relative to the whole sample of 22 clusters at 0.05 < z < 0.25. We also present the detailed surface photometry of 312 early-type galaxies in 7 clusters in the first redshift bin, z~0.025-0.075. We give for each galaxy the complete set of luminosity and geometrical profiles, and and a number of global, photometric and morphological parameters. They have been evaluated taking into account the effects of seeing. Internal consistency checks and comparisons with data in the literature confirm the quality of our analysis. These data, together with the spectroscopic ones presented in the second paper of the series, will provide the local calibration of the scaling relations.

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arXiv2001

WINGS: a Wide-field Imaging Nearby Galaxy clusters Survey

We present a two-band, wide-field imaging survey of an X-ray selected sample of 78 clusters in the redshift range z=0.03-0.07. The aim of the project is to provide the astronomical community with a complete set of homogeneous, CCD-based, surface photometry and morphological data of the nearby cluster galaxies located within 1.5Mpc from the cluster center.

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arXiv2000

Near-infrared photometry of isolated spirals with and without an AGN. II: Photometric properties of the host galaxies

We present the analysis of morphological and photometric properties of a sample of isolated spirals with (18) and without (11) an active nucleus, based on near-infrared imaging in the J and K' bands. The aim of this analysis is to find the differential properties that could be directly connected with the phenomenon of nuclear activity. We stress the importance of using isolated objects for that purpose. Our study shows that both sets of galaxies are similar in their global properties: they define the same Kormendy relation, their disk components share the same properties, the bulge and disk scale lengths are correlated in a similar way, bar strengths and lengths are similar for primary bars. Hosts of isolated Seyfert galaxies have bulge and disk properties comparable to those of isolated non active spirals. Central colors (the innermost 200 pc) of active galaxies are redder than the centers of non active spirals, most probably due to AGN light being re-emitted by the hot dust and/or due to circumnuclear star formation, through the contribution of giants/supergiants. Only one of the Seyfert galaxies in our sample does not present a primary bar,but both primary and secondary bars are equally present in active and control objects. Secondary central elongations (associated with secondary bars, lenses, rings or disks) may be somewhat different. Numerical models indicate that such secondary bars are not strictly necessary to feed the central engine when a primary bar is present. Our results show that down to scales of 100-300 pc, there are no obvious differences between active and non active spiral galaxies.

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arXiv2000

The evolution of the galactic morphological types in clusters

The morphological types of galaxies in nine clusters in the redshift range 0.1<z<0.25 are derived from very good seeing images taken at the NOT and the La Silla Danish telescopes. With the purpose of investigating the evolution of the fraction of different morphological types with redshift, we compare our results with the morphological content of nine distant clusters studied by the MORPHS group, five clusters observed with HST-WFPC2 at redshift z = 0.2-0.3, and Dressler's (1980) large sample of nearby clusters. After having checked the reliability of our morphological classification both in an absolute sense and relative to the MORPHS scheme, we analyze the relative occurrence of elliptical, S0 and spiral galaxies as a function of the cluster properties and redshift. We find a large intrinsic scatter in the S0/E ratio, mostly related to the cluster morphology. In particular, in our cluster sample, clusters with a high concentration of ellipticals display a low S0/E ratio and, vice-versa, low concentration clusters have a high S0/E. At the same time, the trend of the morphological fractions and ratios with redshift clearly points to a morphological evolution: as the redshift decreases, the S0 population tends to grow at the expense of the spiral population, whereas the frequency of Es remains almost constant. We also analyze the morphology-density (MD) relation in our clusters and find that -similarly to higher redshift clusters- a good MD relation exists in the high-concentration clusters, while it is absent in the less concentrated clusters. Finally, the comparison of the MD relation in our clusters with that of the D97 sample suggests that the transformation of spirals into S0 galaxies becomes more efficient with decreasing local density.

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arXiv1999

Near-infrared photometry of isolated spirals with and without an AGN. I: The Data

We present infrared imaging data in the J and K' bands obtained for 18 active spiral galaxies, together with 11 non active galaxies taken as a control sample. All of them were chosen to satisfy well defined isolation criteria so that the observed properties are not related to gravitational interaction. For each object we give: the image in the K' band, the sharp-divided image (obtained by dividing the observed image by a filtered one), the difference image (obtained by subtracting a model to the observed one), the color J-K' image, the ellipticity and position angle profiles, the surface brightness profiles in J and K', their fits by bulge+disk models and the color gradient. We have found that four (one) active (control) galaxies previously classified as non-barred turn out to have bars when observed in the near-infrared. One of these four galaxies (UGC 1395) also harbours a secondary bar. For 15 (9 active, 6 control) out of 24 (14 active, 10 control) of the optically classified barred galaxies (SB or SX) we find that a secondary bar (or a disk, a lense or an elongated ring) is present. The work presented here is part of a large program (DEGAS) aimed at finding whether there are differences between active and non active galaxies in the properties of their central regions that could be connected with the onset of nuclear activity.

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arXiv1999

Effects of interaction on the properties of spiral galaxies. II. Isolated galaxies: The zero point

We analyse the properties of a sample of 22 bright isolated spiral galaxies on the basis of Johnson B,V,I images and optical rotation curves. The fraction of early morphological types in our sample of isolated galaxies (or in other samples of non-interacting spiral galaxies) appears to be smaller than in samples including interacting systems. The overall morphological aspect is regular and symmetric, but all the galaxies present non-axisymmetric components in the form of bars or rings. We find that the color indices become bluer towards the outer parts and that the ir central values are well correlated with the total colors. The properties of the bulges span a larger range than those of the disks, that thus are more alike between them. None of the galaxies shows a truncated, type II disk profile. It is found that the relation between surface brightness and size for the bulges, the Kormendy relation, is tighter when only isolated galaxies are considered. We find a similar relation for the disk parameters with an unprecedented low scatter. A Principal Component Analysis of the measured parameters shows that 2 eigenvectors suffice to explain more than 95% of the total variance. These are, as found for other samples including spiral galaxies in different environmental situations, a scale parameter given by the mass or, equivalently, the luminosity or the size; and a form parameter given by the bulge to disk luminosity ratio, B/D, or, equivalently, by the gradient of the solid-body rotation region of the rotation curve, the G-parameter. We report here a tight correlation between G and B/D for our sample of isolated spirals that could be used as a new distance indicator.

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arXiv1997

The dynamical status of Stephan's Quintet

Multiwavelength data for Stephan's Quintet (SQ) are consistent with the following model for this compact galaxy group. (1) Discordant redshift NGC 7320 is an unrelated foreground galaxy. (2) In the past SQ was an accordant redshift quartet involving NGC 7317, 18A, 19 and 20C. NGC 7320C collided (probably not for the first time) with the group a few times 10$^8$ years ago and stripped the interstellar matter from NGC 7319. (3) In the present SQ is again an accordant quartet involving NGC 7317, 18A,B, and 19. NGC 7318B is now entering the group at high velocity for the first time, giving rise to a shock zone. If most compact groups are like SQ, then they are frequently visited by infalling n eighbors that perturb the group and themselves. SQ represents strong evidence for secondary infall in a small group environment. Tidal stripping reduces the mass of the infalling galaxies, thereby increasing the timescale for their orbital decay. There is little evidence that these high velocity ``intruders'' are rapidly captured and/or merge with the system. Instead they are the mechanism that sustains compact groups against collapse. Efficient gas stripping may account for the low star formation rate observed in compact groups and infall of residual gas into galactic nuclei may also foster the onset of AGN activity.

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arXiv1996

The ESO Nearby Abell Cluster Survey. III. Distribution and Kinematics of Emission-Line Galaxies

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 (0.21) as a result of differences in morphological mix. The average ELG fraction decreases with increasing velocity dispersion of the cluster. Only 1/5 of the clusters shows a significant difference in the average velocities of the ELG and the other (non-ELG) galaxies; in a similar fraction of the clusters significant differences in velocity dispersion are seen. Yet, the velocity dispersion of the ELG is, on average, 20% larger than that of the non-ELG. This larger velocity dispersion is largely intrinsic, i.e. it is not likely to be the result of velocity offsets of the ELG. The surface density of the ELG is significantly less peaked towards the centre than that of the non-ELG. The ELG are distributed fairly smoothly within the cluster with at most 25% in compact substructures. The distribution and kinematics of the ELG yield virial mass estimates that, on average, are 50% higher than those based on the non-ELG. This probably means that the ELG are on more radial orbits than the non-ELG. All observed properties of the ELG are consistent with most of them being on their first approach of the high-density cluster core.

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arXiv1995

The Kinematics of Emission-Line Galaxies in Clusters from ENACS

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 cluster galaxies in substructures. However, only a minor cluster fraction has an ELG population with a mean velocity significantly different from that of the overall cluster population. The velocity distribution of cluster ELG is broader than that of the other cluster galaxies, which translates in a larger observed velocity dispersion. The velocity distribution for ELG in the inner cluster regions suggests that ELG are on mostly radial orbits.

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arXiv1995

The Kinematics of Emission-Line Galaxies in Clusters from ENACS

By using the ENACS data, 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 cluster galaxies in substructures. However, only a minor cluster fraction has an ELG population with a mean velocity significantly different from that of the overall cluster population. The velocity distribution of cluster ELG is broader than that of the other cluster galaxies, which translates in a larger observed velocity dispersion. The velocity distribution for ELG in the inner cluster regions suggests that ELG are on mostly radial orbits.

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arXiv1993

The Peculiar Balmer Line Profiles of OQ 208

We present spectrophotometric observations of the Broad Line Radio Galaxy OQ 208 (Mrk 668, 1404+286) obtained between 1985 and 1991. We show that the Balmer line fluxes and profile shapes undergo remarkable changes. The ratio of intensities between the broad and narrow components of Hbeta increased monotonically from 15 in 1985 to 40 in 1991. The peak of the broad components of Hbeta and Halpha were known to be strongly displaced to the red. We have discovered a correlation between the amplitude of the broad peak displacement and the luminosity of Hbeta, in the sense that the displacement is larger when the line luminosity is higher. We suggest that the observations are not compatible with either a binary Broad Line Region model or one involving ballistic acceleration of the line emitting gas. Radiative acceleration of a system of outflowing clouds readily explains the correlation between line shift and luminosity as well as the peculiar line profiles. Furthermore, it seems that most or all of the Balmer emission originates from the inward face of the clouds. Theoretical line profiles suggest that the observed Hbeta profile is best fit assuming the contribution of an ensemble which might be spherical or confined in a thick disk in addition to a component emitted in a thin shell contained in a cone of half opening angle 12 degrees seen along its axis.

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