Abstracts NGC 5907

Title: HUBBLE SPACE TELESCOPE Imaging of Globular Clusters in the Edge-on Spiral Galaxies NGC4565 and NGC5907

Authors: KISSLER-PATIG, MARKUS; ASHMAN, KEITH M.; ZEPF, STEPHEN E.; FREEMAN, KENNETH C.

Affiliation: AA(European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München, Germany; and University of California ObservatoriessolarLick Observatory, University of California, Santa Cruz, CA 95064; mkissler@eso.org), AB(Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045; ashman@kusmos.phsx.ukans.edu), AC(Department of Astronomy, Yale University, New Haven, CT 06520; zepf@astro.yale.edu), AD(Mount Stromlo and Siding Spring Observatories, Australian National University, Private Bag, Weston Creek Post Office, 2611 Canberra, ACT, Australia; kcf@mso.anu.edu.au)

Journal: The Astronomical Journal, Volume 118, Issue 1, pp. 197-207. (AJ Homepage) Publication Date: 07/1999 Origin: AJ AJ

Keywords: GALAXIES: FORMATION, GALAXIES: INDIVIDUAL (NGC 4565, NGC 5907), GALAXIES: STAR CLUSTERS

Abstract

We present a study of the globular cluster systems of two edge-on spiral galaxies, NGC 4565 and NGC 5907, from WFPC2 images in the F450W and F814W filters. The globular cluster systems of both galaxies appear to be similar to the Galactic globular cluster system. In particular, we derive total numbers of globular clusters of N_GC(4565)=204+/-38^+87_-53 and N_GC(5907)=170+/-41^+47_-72 (where the first are statistical, the second potential systematic errors) for NGC 4565 and NGC 5907, respectively. This determination is based on a comparison with the Milky Way system, for which we adopt a total number of globular clusters of 180+/-20. The specific frequency of both galaxies is S_N~=0.6, indistinguishable from the value for the Milky Way. The similarity in the globular cluster systems of the two galaxies is noteworthy, since they have significantly different thick disks and bulge-to-disk ratios. This would suggest that these two components do not play a major role in the building up of a globular cluster system around late-type galaxies
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Title: A detailed evolutionary model of the disk of the edge-on galaxy NGC5907

Authors: JUST, A.

Affiliation: Astrononisches Rechen-Institut, Mönchhofstraße 12-14, D-69120 Heidelberg, Germany

Journal: AG

Abstract Services, vol. 15. Abstracts of Contributed Talks and Posters presented at the Annual Scientific Meeting of the Astronomische Gesellschaft, in Goettingen, 20-25 September 1999. Publication Date: 00/1999 Origin: AG Bibliographic Code: 1999AGM....15..P95J

Abstract

Nearby edge-on galaxies are a good tool to analyse the star formation history and the dynamical evolution of galactic disks. The analysis is based on detailed models for the vertical structure of the disk (Just et al. 1996, A&A 309, 715). The velocity dispersion and the scale height increase with the age of the stellar populations as can be observed directly in the solar neighbourhood. This evolutionary effect can be used to derive the heating rate and the star formation history from the vertical structure of spiral galaxies seen edge-on. For an analysis of vertical luminosity and colour profiles a detailed model of the stellar composition and a reasonable dust distribution is needed. Since there are radial variations of the disk structure (colour gradients, scale height variations) the local physical models of a self-gravitating disk were extended to include radial dependencies. The disk model of NGC 5907 is based on deep images in U,B,V,R, and I, which we have observed with CAFOS at the 2.2m telescope on Calar Alto. The effects of dust extinction, the age distribution of the stars, and the heating rate are stronly coupled and must be considered all together. We made a multi-colour analysis of the vertical profiles and there radial variations to figure out the star formation history and the dynamical evolution of the disk. The radial colour gradient cannot be an effect of dust extinction but is a sign of a smaller mean age of the disk at larger radii. We give a detailed model of the disk consistent with all available observations.

####################################################################################################################### Title: Ring Structure and Warp of NGC5907: Interaction with Dwarf Galaxies

Authors: SHANG, ZHAOHUI; BRINKS, ELIAS; ZHENG, ZHONGYUAN; CHEN, JIANSHENG; BURSTEIN, DAVID; SU, HONGJUN; BYUN, YONG-IK; DENG, LICAI; DENG, ZUGAN; FAN, XIAOHUI; JIANG, ZHAOJI; LI, YONG; LIN, WEIPENG; MA, FENG; SUN, WEI-HSIN; WILLS, BEVERLEY; WINDHORST, ROGIER A.; WU, HONG; XIA, XIAOYANG; XU, WEN; XUE, SUIJIAN; YAN, HAOJING; ZHOU, XU; ZHU, JIN; ZOU, ZHENLONG

Journal: Astrophysical Journal Letters v.504, p.L23 (ApJ Homepage)

Publication Date: 09/1998

Origin: APJ ApJ

Keywords: GALAXIES: INTERACTIONS, GALAXIES: INDIVIDUAL ALPHANUMERIC: PGC 054419, GALAXIES: INDIVIDUAL NGC NUMBER: NGC 5907, GALAXIES: PHOTOMETRY, GALAXIES: SPIRAL, RADIO LINES: GALAXIES

Abstract

The edge-on, nearby spiral galaxy NGC 5907 has long been used as the prototype of a "noninteracting" warped galaxy. We report here the discovery of two interactions with companion dwarf galaxies that substantially change this picture. First, a faint ring structure is discovered around this galaxy that is likely due to the tidal disruption of a companion dwarf spheroidal galaxy. The ring is elliptical in shape with the center of NGC 5907 close to one of the ring's foci. This suggests that the ring material is in orbit around NGC 5907. No gaseous component to the ring has been detected either with deep H alpha images or in Very Large Array H I 21 cm line maps. The visible material in the ring has an integrated luminosity <=108 Lsolar, and its brightest part has a color R-I~0.9 . All of these properties are consistent with the ring being a tidally disrupted dwarf spheroidal galaxy. Second, we find that NGC 5907 has a dwarf companion galaxy, PGC 54419, which is projected to be only 36.9 kpc from the center of NGC 5907, close in radial velocity ( Delta V=45 km s-1) to the giant spiral galaxy. This dwarf is seen at the tip of the H I warp and in the direction of the warp. Hence, NGC 5907 can no longer be considered noninteracting but is obviously interacting with its dwarf companions much as the Milky Way interacts with its dwarf galaxies. These results, coupled with the finding by others that dwarf galaxies tend to be found around giant galaxies, suggest that tidal interaction with companions, even if containing a mere 1% of the mass of the parent galaxy, might be sufficient to excite the warps found in the disks of many large spiral galaxies.

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Title: NGC5907 revisited: a stellar halo formed by cannibalism?

Authors: LEQUEUX, J.; COMBES, F.; DANTEL-FORT, M.; CUILLANDRE, J. -C.; FORT, B.; MELLIER, Y.

Affiliation: AA(DEMIRM, Observatoire de Paris, 61 Avenue de l'Observatoire, F-75014 Paris, France), AB(DEMIRM, Observatoire de Paris, 61 Avenue de l'Observatoire, F-75014 Paris, France), AC(DEMIRM, Observatoire de Paris, 61 Avenue de l'Observatoire, F-75014 Paris, France), AD(Canada-France-Hawaii Telescope Corporation, P.O. Box 1597, Kamuela, HI 96743, USA), AE(DEMIRM, Observatoire de Paris, 61 Avenue de l'Observatoire, F-75014 Paris, France; Institut d'Astrophysique, 98 bis Bd. Arago, F-75014 Paris, France), AF(DEMIRM, Observatoire de Paris, 61 Avenue de l'Observatoire, F-75014 Paris, France; Institut d'Astrophysique, 98 bis Bd. Arago, F-75014 Paris, France)

Journal: Astronomy and Astrophysics, v.334, p.L9-L12 (1998) (A&A Homepage)

Publication Date: 06/1998 Origin: A&A A&A

Keywords: GALAXIES: NGC 5907, GALAXIES: INTERACTIONS, GALAXIES: KINEMATICS AND DYNAMICS, GALAXIES: PHOTOMETRY, GALAXIES: ABUNDANCES, GALAXIES: HALOS

Abstract

We report on further observations of the luminous halo of NGC 5907. New V, I and B deep photometry confirms the existence of an extended stellar halo redder than the disk. Our data are consistent with a faint halo, or very thick disk, composed of a metal-rich old stellar population. We propose that it could be the remnant of a merged small elliptical, and we support our hypothesis with N-body simulations.