Evidence for Recent Accretion in Nearby Galaxies

Zaritsky, Dennis

doi:10.1086/309586

Cited by 30 publications

(23 citation statements)

References 35 publications

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“…A more plausible explanation for an increase of disk scale height with radial distance might be either the presence of an underlying thick disk with a scale length comparable or larger than the thin disk (Burstein 1979; or recent accretion of material onto the outer disk parts (Tóth & Ostriker 1992;Quinn et al 1993;Zaritsky 1995). However, our observations do not sufficiently support the first of these explanations, i.e.…”

Section: Discussioncontrasting

confidence: 80%

Properties of tidally-triggered vertical disk perturbations

Schwarzkopf

Dettmar

2001

A&A

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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.

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Section: Discussioncontrasting

confidence: 80%

Properties of tidally-triggered vertical disk perturbations

Schwarzkopf

Dettmar

2001

A&A

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“…Toomre & Toomre 1972;Tacconi et al 2002;Dasyra et al 2006;Jesseit et al 2007;Somerville et al 2008;Kormendy et al 2009) and their evolution, although minor mergers most likely constitute the bulk of all galaxy interactions (e.g. Toth & Ostriker 1992;Zaritsky 1995;Hunsberger et al 1996). Investigating how the gas is feeding starburst and AGN activities in these objects is therefore paramount for understanding the overall evolution of the Universe.…”

Section: Introductionmentioning

confidence: 99%

The NGC 1614 interacting galaxy

König

Aalto

Müller

et al. 2013

A&A

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Minor mergers frequently occur between giant and gas-rich low-mass galaxies and can provide significant amounts of interstellar matter to refuel star formation and power active galactic nuclei (AGN) in the giant systems. Major starbursts and/or AGN result when fresh gas is transported and compressed in the central regions of the giant galaxy. This is the situation in the starburst minor merger NGC 1614, whose molecular medium we explore at half-arcsecond angular resolution through our observations of 12 CO (2−1) emission using the Submillimeter Array (SMA). We compare our 12 CO (2−1) maps with optical and Paα, Hubble Space Telescope and high angular resolution radio continuum images to study the relationships between dense molecular gas and the NGC 1614 starburst region. The most intense 12 CO emission occurs in a partial ring with ∼230 pc radius around the center of NGC 1614, with an extension to the northwest into the dust lane that contains diffuse molecular gas. We resolve ten giant molecular associations (GMAs) in the ring, which has an integrated molecular mass of ∼8 × 10 8 M . Our interferometric observations filter out a large part of the 12 CO (1−0) emission mapped at shorter spacings, indicating that most of the molecular gas is diffuse and that GMAs only exist near and within the circumnuclear ring. The molecular ring is uneven with most of the mass on the western side, which also contains GMAs extending into a pronounced tidal dust lane. The spatial and kinematic patterns in our data suggest that the northwest extension of the ring is a cosmic umbilical cord that is feeding molecular gas associated with the dust lane and tidal debris into the nuclear ring, which contains the bulk of the starburst activity. The astrophysical process for producing a ring structure for the final resting place of accreted gas in NGC 1614 is not fully understood, but the presence of numerous GMAs suggests an orbit-crowding or resonance phenomenon. There is some evidence that star formation is progressing radially outward within the ring, indicating that a self-triggering mechanism may also affect star formation processes. The net result of this merger therefore very likely increases the central concentration of stellar mass in the NGC 1614 remnant giant system.

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“…According to a series of papers on the frequency of these so called "soft merging" events (e.g. Toth & Ostriker 1992;Zaritsky 1995Zaritsky , 1996 a large number of present-day (disk-) galaxies were affected by merging-or accretion processes of this magnitude since they have formed. As a consequence, interactions and minor mergers within this mass range might modify our picture of galaxy formation and evolution.…”

Section: Introductionmentioning

confidence: 99%

The influence of interactions and minor mergers on the structure of galactic disks

Schwarzkopf

Dettmar

2000

Astron. Astrophys. Suppl. Ser.

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Abstract. This paper is the first part in our series on the influence of tidal interactions and minor mergers on the radial and vertical disk structure of spiral galaxies. We report on the sample selection, our observations, and data reduction. Surface photometry of the optical and near infrared data of a sample of 110 highly-inclined/edge-on disk galaxies are presented. This sample consists of two subsamples of 61 non-interacting galaxies (control sample) and of 49 interacting galaxies/minor merging candidates. Additionally, 41 of these galaxies were observed in the near infrared. We show that the distribution of morphological types of both subsamples is almost indistinguishable, covering the range between 0 ≤ T ≤ 9. An improved, 3-dimensional disk modelling-and fitting procedure is described in order to analyze and to compare the disk structure of our sample galaxies by using characteristic parameters. We find that the vertical brightness profiles of galactic disks respond very sensitive even to small deviations from the perfect edge-on orientation. Hence, projection effects of slightly inclined disks may cause substantial changes in the value of the disk scale height and must therefore be considered in the subsequent study.

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Evidence for Recent Accretion in Nearby Galaxies

Cited by 30 publications

References 35 publications

Properties of tidally-triggered vertical disk perturbations

Properties of tidally-triggered vertical disk perturbations

The NGC 1614 interacting galaxy

The influence of interactions and minor mergers on the structure of galactic disks

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