Properties of tidally-triggered vertical disk perturbations

Abstract

Abstract. We present a detailed analysis of the properties of warps and tidally-triggered perturbations perpendicular to the plane of 47 interacting/merging edge-on spiral galaxies. The derived parameters are compared with those obtained for a sample of 61 non-interacting edge-on spirals. The entire optical (R-band) sample used for this study was presented in two previous papers. We find that the scale height of disks in the interacting/merging sample is characterized by perturbations on both large ( disk cut-off radius) and short ( z0) scales, with amplitudes of the order of 280 pc and 130 pc on average, respectively. The size of these large (short) -scale instabilities corresponds to 14% (6%) of the mean disk scale height. This is a factor of 2 (1.5) larger than the value found for non-interacting galaxies. A hallmark of nearly all tidally distorted disks is a scale height that increases systematically with radial distance. The frequent occurrence and the significantly larger size of these gradients indicate that disk asymmetries on large scales are a common and persistent phenomenon, while local disturbances and bending instabilities decline on shorter timescales. Nearly all (93%) of the interacting/merging and 45% of the non-interacting galaxies studied are noticeably warped. Warps of interacting/merging galaxies are ≈2.5 times larger on average than those observed in the non-interacting sample, with sizes of the order of 340 pc and 140 pc, respectively. This indicates that tidal distortions do considerably contribute to the formation and size of warps. However, they cannot entirely explain the frequent occurrence of warped disks.

The Warped Disk of Integral-Sign Galaxy PGC 20348

“…As shown in Fig.5, the radial gradient of disk scale height dz o /dr is very small, dz o /dr = 0.02 ± 0.01. The positive radial gradient is consistent with the general behavior of disk scale heights for warped disks (Schwarzkopf & Dettmar 2001).…”

“…Similar flarings and radial increase of disk scale heights were observed in VV 490 that has a close companion (Reshetnikov & Combes 1996. Such a radial increase of disk scale heights is a general property of tidally perturbed disks (Schwarzkopf & Dettmar 2001) which can be explained by the tidal heating by companions or merged satellites (Töth & Ostriker 1992;Mihos et al 1995).…”

“…However, there are a number of galaxies that display significant variations of disk scale heights (de Grijs & van der Kruit 1966;Reshetnikov & Combes 1996. In particular, interacting/merging galaxies tend to have increasing disk scale height with increasing galactocentric distance (Schwarzkopf & Dettmar 2001). Moreover, there are some galaxies showing similar behavior of disk scale height in non-interacting galaxies (de Grijs & Peletier 1997).…”

Molecular Clouds in the Extreme Outer Galaxy between l = 34.°75 to 45.°25

“…In the outer galactic disk, warp is a common feature in spiral galaxies, with amplitude increasing with galactic radius (e.g., Reshetnikov & Combes 1998;Schwarzkopf & Dettmar 2001;Reshetnikov et al 2002;Kalberla & Kerp 2009;Hou & Han 2014). Early HI emission surveys have first revealed that the disk of our Galaxy is warped beyond the Solar circle (e.g., Burke 1957;Kerr 1957;Burton 1988).…”

Warps and Accretion

“…Probably every galaxy shows a warp (Sancisi 1976, Sánchez-Saavedra et al 1990, Reshetnikov & Combes 1998, Reshetnikov & Combes 1999, Schwarzkopf & Dettmar 2001, Sánchez-Saavedra et al 2003, Ann & Park 2006. Traced out to the largest radii in the H i emission line, warps seem in most cases, while asymmetric, to be dominated by a grand-design S-shaped pattern (García-Ruiz et al 2002).…”