J. D. Santander-Vela

The AMIGA sample of isolated galaxies III. IRAS data and infrared diagnostics

Aims. We describe the mid- (MIR) and far- (FIR) infrared properties of a large (∼1000) sample of the most isolated galaxies in the local Universe. This sample is intended as a “nurture-free” zero point against which more environmentally influenced samples can be compared. Methods. We reprocess IRAS MIR/FIR survey data using the ADDSCAN/SCANPI utility for 1030 out of 1050 galaxies from the Catalogue of Isolated Galaxies (CIG) as part of the AMIGA project. We focus on diagnostics (FIR luminosity LFIR, R = log(LFIR/LB), and IRAS colours) thought to be sensitive to effects of environment or interaction. Results. The distribution of log(LFIR) sharply peaks from 9.0–10.5, with very few (<2%) galaxies above 10.5. Review of available optical images of the most FIR luminous galaxies finds the majority likely to be interacting systems missed in our earlier morphological reevaluation. The optically normalised luminosity diagnostic R = log(LFIR/LB) shows a sharply peaked distribution between 0.0 and −1.0. These results were compared to the magnitude limited sample of the Center for Astrophysics that was selected without environmental discrimination. This modestly (e.g., compared to cluster, binary galaxy, and compact group samples) environmentally affected sample shows a significantly higher mean log(LFIR), and R, whereas the mean log(LB) is the same. Our sample shows a strong LFIR vs. LB correlation, with a slope steeper than one (LFIR ∝ L 1.41 B ). Interacting galaxies were found above this correlation, showing an enhancement in LFIR. With respect to the IRAS colours, we found higher F60/F100 values for ellipticals and late-type galaxies than for spirals, indicating a higher dust temperature. The mean value of F60/F100 was found to be lower than for interacting samples from the literature. Conclusions. The results indicate that the FIR emission is a variable enhanced by interaction, and that our sample probably shows the lowest possible mean value. This attests to the utility of our sample for defining a nurture-free zero point.

ARE (PSEUDO)BULGES IN ISOLATED GALAXIES ACTUALLY PRIMORDIAL RELICS

We present structural parameters and (g – i) bulge/disk colors for a large sample (189) of isolated AMIGA galaxies. The structural parameters of bulges were derived from the two-dimensional bulge/disk/bar decomposition of Sloan Digital Sky Survey i-band images using GALFIT. Galaxies were separated between classical bulges (nb > 2.5) and pseudobulges (nb < 2.5), resulting in a dominant pseudobulge population (94%) with only 12 classical bulges. In the μ e -R e plane, pseudobulges are distributed below the elliptical relation (smaller R e and fainter μ e ), with the closest region to the Kormendy relation populated by those pseudobulges with larger values of B/T. We derived (g – i) bulge colors using aperture photometry and find that pseudobulges show median colors (g – i) b ~ 1.06, while their associated disks are much bluer, (g – i) d ~ 0.77. Moreover, 64% (113/177) of pseudobulges follow the red sequence of early-type galaxies. Bluer pseudobulges tend to be located in galaxies with the highest likelihood of tidal perturbation. The red bulge colors and low B/T values for AMIGA isolated galaxies are consistent with an early formation epoch and not much subsequent growth. Properties of bulges in isolated galaxies contrast with a picture where pseudobulges grow continuously via star formation. They also suggest that environment could be playing a role in rejuvenating the pseudobulges.

The AMIGA sample of isolated galaxies - XII. Revision of the isolation degree for AMIGA galaxies using the SDSS

Context. To understand the evolution of galaxies, it is necessary to have a reference sample where the e ect of the environment is minimized and quantified. In the framework of the AMIGA project (Analysis of the interstellar Medium of Isolated GAlaxies), we present a revision of the environment for galaxies in the Catalogue of Isolated Galaxies (CIG, Karachentseva 1973, Astrof. Issledovaniia Byu. Spec. Ast. Obs., 8, 3) using the ninth data release of the Sloan Digital Sky Survey (SDSS-DR9). Aims. The aims of this study are to refine the photometric-based AMIGA sample of isolated galaxies and to provide an improvement of the quantification of the isolation degree with respect to previous works, using both photometry and spectroscopy. Methods. We developed an automatic method to search for neighbours within a projected area of 1 Mpc radius centred on each primary galaxy to revise the CIG isolation criteria introduced by Karachentseva (1973). The local number density at the fifth nearest neighbour and the tidal strength a ecting the CIG galaxy were estimated to quantify the isolation degree. Results. Of the 636 CIG galaxies considered in the photometric study, 426 galaxies fulfil the CIG isolation criteria within 1 Mpc, taking into account projected neighbours. Of the 411 CIG galaxies considered in the spectroscopic study, 347 galaxies fulfil the CIG isolation criteria when a criterion about redshift di erence is added. The available redshifts allow us to reject background neighbours and thus improve the photometric assessment. On average, galaxies in the AMIGA sample show lower values in the local number density and the tidal strength parameters than galaxies in denser environments such as pairs, triplets, compact groups, and clusters. Conclusions. For the first time, the environment and the isolation degree of AMIGA galaxies are quantified using digital data. The use of the SDSS database permits one to identify fainter and smaller-size satellites than in previous AMIGA works. The AMIGA sample is improved by this study, because we reduced the sample of isolated galaxies used in previous AMIGA works by about 20%. The availability of the spectroscopic data allows us to check the validity of the CIG isolation criteria, which is not fully e cient. About 50% of the neighbours considered as potential companions in the photometric study are in fact background objects. We also find that about 92% of the neighbour galaxies that show recession velocities similar to the corresponding CIG galaxy are not considered by the CIG isolation criteria as potential companions, which may have a considerable influence on the evolution of the central CIG galaxy.

Effects of the environment on galaxies in the Catalogue of Isolated Galaxies: physical satellites and large scale structure

Context. We present a study of the 3D environment for a sample of 386 galaxies in the Catalogue of Isolated Galaxies (CIG, Karachentseva 1973) using the Ninth Data Release of the Sloan Digital Sky Survey (SDSS-DR9). Aims. We aim to identify and quantify the e ects of the satellite distribution around a sample of galaxies in the CIG, as well as the e ects of the large-scale structure (LSS). Methods. To recover the physically bound galaxies we first focused on the satellites that are within the escape speed of each CIG galaxy. We also propose a more conservative method using the stacked Gaussian distribution of the velocity di erence of the neighbours. The tidal strengths a ecting the primary galaxy were estimated to quantify the e ects of the local and LSS environments. We also defined the projected number density parameter at the fifth nearest neighbour to characterise the LSS around the CIG galaxies. Results. Out of the 386 CIG galaxies considered in this study, at least 340 (88% of the sample) have no physically linked satellite. Following the more conservative Gaussian distribution of physical satellites around the CIG galaxies leads to upper limits. Out of the 386 CIG galaxies, 327 (85% of the sample) have no physical companion within a projected distance of 0.3 Mpc. The CIG galaxies are distributed following the LSS of the local Universe, although presenting a large heterogeneity in their degree of connection with it. When present around a CIG galaxy, the e ect of physically bound galaxies largely dominates (typically by more than 90%) the tidal strengths generated by the LSS. Conclusions. The CIG samples a variety of environments, from galaxies with physical satellites to galaxies without neighbours within 3 Mpc. A clear segregation appears between early-type CIG galaxies with companions and isolated late-type CIG galaxies. Isolated galaxies are in general bluer, with probably younger stellar populations and very high star formation compared with older, redder CIG galaxies with companions. Reciprocally, the satellites are redder and with an older stellar populations around massive early-type CIG galaxies, while they have a younger stellar content around massive late-type CIG galaxies. This suggests that the CIG is composed of a heterogeneous population of galaxies, sampling from old to more recent, dynamical systems of galaxies. CIG galaxies with companions might have a mild tendency (0.3 0.4 dex) to be more massive, and may indicate a higher frequency of having su ered a merger in the past.

Virtual Observatory Activities in the AMIGA Group

The AMIGA (Analysis of the interstellar Medium of Isolated GAlaxies) project is an international collaboration led from the Instituto de Astrofisica de Andalucia (CSIC). The group’s experience in radio astronomy databases turned, as a natural evolution, into an active participation in the development of data archives and radio astronomy software. The contributions of the group to the Virtual Observatory (VO) have been mostly oriented towards the deployment of large VO compliant databases and the development of access interfaces (IRAM 30 m Pico Veleta, DSS–63 70 m in Robledo de Chavela). We also have been working in the development of an API for VO tools that will ease access to VO registries and communication between different VO software. A collaboration with the Kapteyn Astronomical Institute has started recently in order to perform a complete renovation of the only existing high-level software (GIPSY) for the analysis of datacubes, allowing its fully integration in the VO.

Building a VO-compliant Radio Astronomical DAta Model for Single-dish radio telescopes (RADAMS)

The Virtual Observatory (VO) is becoming the de-facto standard for astronomical data publication. However, the number of radio astronomical archives is still low in general, and even lower is the number of radio astronomical data available through the VO. In order to facilitate the building of new radio astronomical archives, easing at the same time their interoperability with VO framework, we have developed a VO-compliant data model which provides interoperable data semantics for radio data. That model, which we call the Radio Astronomical DAta Model for Single-dish (RADAMS) has been built using standards of (and recommendations from) the International Virtual Observatory Alliance (IVOA). This article describes the RADAMS and its components, including archived entities and their relationships to VO metadata. We show that by using IVOA principles and concepts, the effort needed for both the development of the archives and their VO compatibility has been lowered, and the joint development of two radio astronomical archives have been possible. We plan to adapt RADAMS to be able to deal with interferometry data in the future.

A VO Archive for the DSS-63 Antenna at Robledo

In this contribution we describe the development of a Virtual Observatory (VO) Archive for the DSS-63 antenna of the NASA Deep Space Communication Complex in Robledo de Chavela (Madrid). In an initial step the archive includes observations in the K-band (18–26 GHz) of the mentioned antenna with a future extension to other ranges, in particular the Q-band (40–50 GHz) and the Ka-band (32 GHz). A first version of the archive will be available from the LAEFF Scientific Data Centre1 by the end of 2008. This work is the result of a collaboration between the AMIGA group of the IAA–CSIC and the SVO and Radioastronomy groups at LAEFF and forms part of a pioneering initiative to integrate radio astronomical data and services in the Virtual Observatory.

THE FAR-INFRARED PROPERTIES OF THE MOST ISOLATED GALAXIES

We describe the mid- (MIR) and far- (FIR) infrared properties of a large (~1000) sample of the most isolated galaxies in the local Universe. This sample is intended as a “nurture-free” zero point against which more environmentally influenced samples can be compared. We reprocess IRAS MIR/FIR survey data using the ADDSCAN/SCANPI utility for 1030 out of 1050 galaxies from the Catalogue of Isolated Galaxies (CIG) as part of the AMIGA project. We focus on diagnostics (FIR luminosity L FIR , R = log( L FIR / L B ) and IRAS colours) thought to be sensitive to effects of environment or interaction. The distribution of log( L FIR ) is sharply peaked from 9.0–10.5 with very few ( R = log( L FIR / L B ) shows a distribution sharply peaked between 0.0 and −1.0. These results were compared to the magnitude limited CfA sample that was selected without environmental discrimination. This modestly (e.g. compared to cluster, binary galaxy and compact group samples) environmentally affected sample shows significantly higher mean log( L FIR ) and R , whereas the mean log( L B ) is the same. Our sample shows a strong L FIR vs. L B correlation, with a slope steeper than one ( L FIR ∝ L 1.41 B ). Interacting galaxies were found above this correlation, showing an enhancement in L FIR . With respect to the IRAS colours, we found higher F 60 / F 100 value for ellipticals and late-type galaxies than for spirals, indicating a higher dust temperature. The mean value of F 60 / F 100 was found to be lower than for interacting samples from the literature. The results indicate that the FIR emission is a variable enhanced by interaction, and that our sample probably shows the lowest possible mean value. This attests to the utility of our sample for defining a nurture-free zero point. More details can be found in the paper ( The AMIGA sample of isolated galaxies, III. IRAS data and infrared diagnositics , U. Lisenfeld et al .) which is accepted for publication in Astronomy & Astrophysics.