<i>ROSAT</i>-<i>HRI</i>observations of six southern galaxy pairs

Trinchieri, G.; Rampazzo, R.

doi:10.1051/0004-6361:20010750

Cited by 9 publications

(18 citation statements)

References 38 publications

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“…In contrast to their similar optical characteristics, their X-ray properties (see also Trinchieri & Rampazzo 2001) indicate that their X-ray luminosities, L X /L B ratios and morphologies are very different, which implies that they have different origins and/or represent different evolutionary stages of the systems. X-ray emission in RR 143 and RR 242 is centred on the elliptical but is much more extended than the optical light.…”

Section: Introductionmentioning

confidence: 99%

Small-scale systems of galaxies

Grützbauch

Zeilinger

Rampazzo

et al. 2009

A&A

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Context. In hierarchical evolutionary scenarios, isolated, physical pairs may represent an intermediate phase, or "way station", between collapsing groups and isolated elliptical (E) galaxies (or fossil groups). Aims. We started a comprehensive study of a sample of galaxy pairs composed of a giant E and a spiral (S) with the aim of investigating their formation/evolutionary history from observed optical and X-ray properties. Methods. We present VLT-VIMOS observations designed to identify faint galaxies associated with the E+S systems from candidate lists generated using photometric criteria on WFI images covering an area of ∼0.2 h −1 100 Mpc radius around the pairs. Results. We found two and ten new members likely to be associated with the X-ray bright systems RR 143 and RR 242, respectively. The X-ray faint RR 210 and RR 216, which were only partially covered by the VIMOS observations, have two and three new faint members, respectively. The new members increase the number of associated galaxies to 4, 7, 6, and 16 for RR 143, RR 210, RR 216, and RR 242, respectively, down to M R ∼ −12 + 5 log h 100 . We derive structural properties of the faint members from surface photometry. The faint galaxy population of all the systems is dominated by disk galaxies, 40% being S0s with generally low bulge to total light ratios. A small fraction of the faint companions show signatures of interaction. A remarkable shell system is detected in the early-type galaxy RR 242_24532. We also derive dynamical properties and optical luminosity functions for the 4 groups. Conclusions. The above results are discussed in the context of the evolution of poor galaxy group associations. A comparison between the optical luminosity functions (OLFs) of our E+S systems and a sample of X-ray bright poor groups suggest that the OLF of X-ray detected poor galaxy systems is not universal. The OLF of our X-ray bright systems suggests that they are more dynamically evolved than our X-ray faint sample and some X-ray bright groups in the literature. However, we suggest that the X-ray faint E+S pairs represent a phase in the dynamical evolution of some X-ray bright poor galaxy groups. The recent or ongoing interaction in which the E member of the X-ray faint pairs is involved could have decreased the luminosity of any surrounding X-ray emitting gas.

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Section: Introductionmentioning

confidence: 99%

Small-scale systems of galaxies

Grützbauch

Zeilinger

Rampazzo

et al. 2009

A&A

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“…We have presently only very limited information on the X-ray properties of mixed pairs Henriksen & Cousineau 1999;Trinchieri & Rampazzo 2001) with detected ETG members showing X-ray luminosities and L X /L B ratios that span the full range observed for early-type galaxies in general. A group-like extension has been detected in some pairs but there is no evidence that pair membership affects the global X-ray properties of galaxies (Trinchieri & Rampazzo 2001). Detection of diffuse X-ray emission in some pairs might offer the best means to identify systems that are actively involved in a hierarchical merging process.…”

Section: Introductionmentioning

confidence: 99%

“…In the above context we present: 1) new XMM-Newton observations of two E+S pairs (RR 143 and RR 242) both of which show diffuse emission (plus pairs RR 210 and RR 216 previously observed with ROSAT (Trinchieri & Rampazzo 2001)) and 2) results of an optical photometric search for tidal features/optical diffuse light and a study of candidate faint galaxy populations that might be associated with the pairs. Groups studied by Zabludoff & Mulchaey (1998) revealed a significantly higher number of faint galaxies (≈50 members down to magnitudes as faint as M B ≈ -14 +5log 10 h 100 ) in groups with a hot IGM compared to groups without this component.…”

Section: Introductionmentioning

confidence: 99%

Small-Scale Systems of Galaxies. III. X-Ray-detected Elliptical+Spiral Galaxy Pairs in Low-Density Environments

et al. 2006

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We present a comprehensive study of the local environments of four E+S galaxy pairs with the main goal to investigate their formation/evolution histories.We obtained new XMM-Newton data for two pairs (RR 143 and RR 242) that complements existing ROSAT data for the other two (RR 210 and RR 216). The new observations reveal diffuse X-ray emission in both pairs with luminosities of L X ∼ 3 × 10 41 erg s −1 (0.5-2.0 keV). The emission is asymmetric in both cases and extends out to ∼ 500 ′′ (120 kpc) and 700 ′′ (160 kpc) in RR 143 and RR 242 respectively. The nucleus of RR 242 hosts a low luminosity (L X ∼ 10 41 erg s −1 , 2.0-10 keV) mildly absorbed (N H ∼ 10 22 cm −2 ) AGN. We find that the early-type components of pairs with diffuse hot gas appear to be relaxed objects while those in RR 210 and RR 216, where no diffuse emission has been found, display unambiguous signatures of ongoing interaction.New wide-field V and R-band observations are used to study the photometric properties of the early-type components and to search for candidate faint galaxy populations around each of the pairs. While no diffuse optical light is found for any of the pairs, all of the early-type members show very extended and concentric luminous envelopes. We identify a faint galaxy sample in each field and we consider whether they could be physically associated with the luminous pairs based upon (V − R) colors and photometric properties. We find that the distribution of r e and M R for the candidates are similar in three of the fields (RR 143, 216 and 242). The same selection criteria applied to the field of RR 210 suggest a fainter and more compact population possibly suggesting a larger background fraction than in the other fields.

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“…Recent X‐ray studies have shown that a significant amount of a diffuse emission could be present in galaxy groups (Mulchaey et al 1993, 1996, 2003; Ponman et al 1996; Mulchaey 2000; Gomez et al 2003, see, for example,) and even in physical pairs composed of an elliptical and a spiral member (Rampazzo et al 1998; Henriksen & Cousineau 1999; Trinchieri & Rampazzo 2001). However, it is still unclear whether massive groups, whose dominant galaxy is a spiral, do exist (Mulchaey 2000; Kelm & Focardi 2004).…”

Section: Introductionmentioning

confidence: 99%

Optical properties of the NGC 5328 group of galaxies

Grützbauch

Annibali

Bressan

et al. 2005

Monthly Notices of the Royal Astronomical Society

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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 (H_0 = 70 km/s/Mpc). We analyze the galaxy structure and study the emission line properties of the group members looking for signatures of star formation and AGN activity. We finally attempt to infer, from the modeling of line-strength indices, the stellar population ages of the early-type members. We investigate also the presence of a dwarf galaxy population associated with the bright members. The group is composed of a large fraction of early-type galaxies including NGC 5328 and NGC 5330, two bona fide ellipticals at the center of the group. In both galaxies no recent star formation episodes are detected by the H_beta vs. MgFe indices of these galaxies. 2MASX J13524838-2829584 has extremely boxy isophotes which are believed to be connected to a merging event: line strength indices suggest that this object probably had a recent star formation episode. A warped disc component emerges from the model subtracted image of 2MASX J13530016-2827061 which is interpreted as a signature of an ongoing interaction with the rest of the group. Ongoing star formation and nuclear activity is present in the projected outskirts of the group. The two early-type galaxies 2MASX J13523852-2830444 and 2MASX J13525393-2831421 show spectral signatures of star formation, while a Seyfert 2 type nuclear activity is detected in MCG -5-33-29.Comment: 18 pages, 12 figures, accepted for publication in MNRA

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ROSAT-HRIobservations of six southern galaxy pairs

Cited by 9 publications

References 38 publications

Small-scale systems of galaxies

Small-scale systems of galaxies

Small-Scale Systems of Galaxies. III. X-Ray-detected Elliptical+Spiral Galaxy Pairs in Low-Density Environments

Optical properties of the NGC 5328 group of galaxies

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