The existence and shapes of dust lanes in galactic bars

“Bars in bulge-dominated, early-type spirals tend to be very strong and efficient at transporting gas from the disk into the central regions, while bars in late-type galaxies are much weaker and are predicted to be much less efficient in transporting gas (e.g. Athanassoula 1992, Friedli & Benz 1995).”

“Calculations of orbits in barred potentials reveal other orbit families (e. g., Contopolous & Mertzanides 1977; Athanassoula 1992a,b; SW93), only a few of which are relevant here.”

“…moves inward from∼ 150 pc at a mean rate of 0.2–2 km s−1, which is comparable to the estimate of 0.3 km s−1 for inward radial motion near the solar circle in spiral structure models (Lacey & Fall 1985) and to the azimuthally averaged inflow velocities found in the bar models of Athanassoula (1992).”

“As the amplitude of the perturbation increases the bifurcations are substituted by gaps, but one can still say that an ILR resonance exists if and only if these x2 and x3 families exist (e.g. van Albada & Sanders 1982, Athanassoula 1992).”

“It is well known that gas Ñows in barred potentials produce large-scale shocks o†set from the bar major axis (e.g., Athanassoula 1992).”

“…2006), although they are also associated with enhanced nuclear and circumnuclear star formation (Ho, Filippenko & Sargent 1997), and frequently exhibit dust lanes, which is a signature of radially inflowing gas (Kormendy 1982; Athanassoula 1992; Sellwood & Wilkinson 1993; Friedli & Benz 1993).”

“Figure 16 shows such a result from the high quality simulations by Athanassoula (1992b).”

“Hydrodynamical simulations have shown that bars induce angular momentum transfer via gravitational torques, which result in radial flows and mixing of both stars and gas (e.g., Athanassoula 1992).”

“Indeed, orbital structure theory shows that the maximum extent of the x2 orbits is smaller than or of the order of the extent of the bar minor axis (Athanassoula 1992a, fig.”

“Large-scale bars are known to extend to about (0.83 ± 0.12) of their corotation radii, an empirical rule based on the shapes of their offset dust lanes (Athanassoula 1992).”

“The effect of a bar on the gas kinematics is significant in the inner galaxy (Athanassoula 1992; Weiner and Sellwood 1992; Fux 1997, 1999; Mulder and Liem 1986).”

“Models show that the non-axisymmetric bar potential induces large scale streaming motions in the stars and gas (Sellwood & Wilkinson 1993 and references therein, Athanassoula 1992a,b).”

“…of other spiral galaxies and with simulations that show that a strong rotating bar sweeps up the gas and dust in its vicinity There seems(Athanassoula 1992b). to be a current consensus that rings form at the inner second harmonic resonance just inside the(Schwartz 1984), corotation…”

“In studies in which ellipse fits are used to characterize bars, the maximum ellipticity of the bar (ebar) is used as a measure of bar strength (e.g., Athanassoula 1992a; Martin 1995; Wozniak et al. 1995; Jogee et al. 1999, 2002a, 2002b; Knapen et al. 2000; Laine et al. 2002).”

“The “pile up” of material in these shocks manifests itself observationally as dust lanes and enhanced star formation in the leading edge of spiral arms (Roberts et al. 1979; Athanassoula 1992b; Wada 1994; Bournaud et al. 2005).”

“This motion is also expected to generate intense shear in the gas lanes (e.g., Athanassoula 1992; Sheth et al. 2002) that could prevent the formation of massive objects through the inhibition of the density fluctuations that become the seeds of massive GMCs (Hopkins 2012).”

“Gaseous spiral arms driven by a bar have since been seen in many further simulations (e.g. Schwarz 1981; Combes & Gerin 1985; Athanassoula 1992; Wada 1994; Englmaier & Gerhard 1999; Bissantz, Englmaier, & Gerhard 2003; Rodriguez-Fernandez & Combes 2008).”

“The latter stalls in the inner few 100 pc because shocks associated with the bar weaken, and gravitational torques in the vicinity of ILRs may even reverse (e.g., Combes & Gerin 1985; Shlosman et al. 1989; Athanassoula 1992).”

“Gaseous response to the nonaxisymmetric potential has been well studied numerically (e.g., Athanassoula 1992 ; Wada & Habe 1992, 1995 ; Englmaier & Gerhard 1997) and analytically (e.g., Yuan & Cheng 1989 ; Wada 1994 ; Lindblad & Lindblad 1994).”

“The orbits lie in a plane and resemble the velocity and density patterns in the bar models of Athanassoula (1992).”

“This SPH method was tested for barred galaxy applications by verifying that the properties of shocks forming in such models agree with those found by Athanassoula (1992b) with a grid-based method.”

“Athanassoula (1992)showed convincingly thatthese arethelocusofshocks.”

“The bar’s corotation radius was arbitrarily set to rCR = 2.4 kpc, consistent with the notions that the bar terminates somewhat inside corotation (Contopoulos & Papayannopoulos 1980; Sellwood & Sparke 1988; Athanassoula 1992b) and that the region around corotation is depopulated of gas.”

“This may explain why there is a mostly gas-free gap in the hydrodynamic simulations between the last non-intersecting x1-orbit and the first accessible x2-orbit, without any clear off-axis shocks such as those found in other barred galaxy models (e.g. Athanassoula 1992).”

“Many theoretical studies and numerical simulations have shown that a bar can play an important role in gas-fueling toward the central region (Combes & Gerin 1985; Pfenniger & Norman 1990; Athanassoula 1992; Wada & Habe 1995).”

“In particular, Athanassoula (1992a) studied orbits in analytic potentials of barred galaxies and showed that generalized ellipses are a good representation of the main barsupporting stellar orbits.”

“In barred galaxies the gas is driven inward along shocks that may be delineated by dust lanes (Roberts et al. 1979; Athanassoula 1992; Shlosman 1999; Shlosman 2001).”

“In most barred galaxies, gas is concentrated on the leading side of the bar (e.g., de Vaucouleurs & de Vaucouleurs 1963), which is reproduced in numerical simulations (e.g., Athanassoula 1992).”

“And, in particular, they may be closely associated with the secular evolution processes that form pseudo-bulges and destroy bars (e.g., Athanassoula 1992a,b; Norman et al. 1996; Carollo 1999; Kormendy & Kennicutt 2004).”

“10 43 erg s−1; Athanassoula 1992; Ho et al. 1997; Regan & Mulchaey 1999; Cisternas et al. 2015; Cheung et al. 2015; Goulding et al. 2017).”

“Star formation is thought to be inhibited in the strongest bars because of strong shocks and high shear (Athanassoula 1992; Sheth et al. 2005; but see Zurita et al. (2004) who suggest shocks help trigger star formation).”

“For instance, they are able to contribute to the redistribution of matter in the galaxy by exchanging angular momentum with the disc, inducing gas flows (Athanassoula 1992; Friedli 1998).”

“The nonaxisymmetric poten- tial due to a large-scale bar leads to the formation of a shock front along the bar’s leading edges (Prendergast 1983; Athanassoula 1992) and material has been observed flowing into the central regions of several barred galaxies (Quillen et al. 1995; Regan, Vogel, &…”

“Bars are in fact preceded by dust lanes in their motion, which have been recognized as related to shocks in the gas flow, and correspond to the regions of highest gas density (e.g. Athanassoula 1992).”

“For the purpose of this work, we adopt a radial inflow velocity profile induced by a bar of current size RB = 3. kpc, having a corotation radius at RC = 1.2 RB, which is a typical relation between bar length and corotation radius (e.g. Athanassoula 1992).”

“Not only can a bar be strong in the inner parts and weak in the outer parts (or vice versa), but many parameters influence the dynamics (e.g., bar axial ratio, mass, pattern speed; e.g., Athanassoula 1992a, 1992b).”

“Simulations of gas flow in barred galaxies (e.g., Athanassoula 1992; Shaw et al. 1993; Piner, Stone, & Teuben 1995) suggest that nuclear gas rings can lie both parallel and perpendicular to their host bars, or else at oblique angles with the major axis of the ring leading the bar (but see Heller,…”

“…discs, stellar and/or gaseous, are also examples of CMCs. Gaseous such discs are expected to form particularly frequently in barred galaxies, due to the gas inflow driven by the bar (Athanassoula 1992b; Wada & Habe 1992, 1995; Friedli & Benz 1993; Heller & Shlosman 1994; Regan & Teuben 2004).”

“The dust lanes along the leading edge of the bar are always very straight in strongly barred galaxies (Athanassoula 1992; Piner et al. 1995).”

“Athanassoula (1992) used it to study gas flow patterns in a variety of model galaxy potentials.”

“…of angular momentum allows bars to drive gas, and to a lesser extent, stars, to the centers of galaxies (Matsuda & Nelson 1977; Simkin et al. 1980; Athanassoula 1992; Wada & Habe 1992, 1995; Friedli & Benz 1993; Heller & Shlosman 1994; Knapen et al. 1995; Sakamoto et al. 1999; Sheth et al. 2005).”

“Subsequent Evolution Numerical simulations show that bars in galactic disks can be induced by galactic interactions and are very effective at driving material toward the central regions of galaxies (e.g., Combes & Gérin 1985; Noguchi 1987, 1988; Shlosman, Frank, & Begelman 1989; Athanassoula 1992).”

“efficiently transfer angular momentum within the disc, allowing gas to move inwards [134, 135, 136, 137, 138].”

“An efficient way to drag significant amount of mass in the central regions would be the presence of a large scale bar in the host galaxy, which could initiate strong inflows of gas (e.g. Athanassoula 1992; Friedli & Benz 1993).”

“…galaxy in a variety of ways e.g. by pushing gas to the central regions, where it can form nuclear structures such as nuclear discs and rings (e.g. Athanassoula 1992; Knapen et al. 2002; Comerón et al. 2010; Ellison et al. 2011; Fragkoudi et al. 2016; Sormani et al. 2018; de Lorenzo-Cáceres et…”

“These straight dust lanes are expected for gas and dust compressed in the principal shocks along the leading edges of a bar (e.g., Athanassoula 1992).”

“This star formation suggests that the bar is relatively weak (Athanassoula 1992).”

“In all these works bar strength is estimated indirectly from the ellipticity of a bar, based on the analytical work by Athanassoula (1992a).”

“…previous observational (e.g., Sakamoto et al. 1999, Jogee et al. 2005, Sheth et al. 2005) as well as analytical andnumerical studies (e.g., Sanders & Huntley 1976, Shlosman, Frank & Begelman 1989, Athanassoula 1992; Berentzen et al. 1998; Regan & Teuben 2004, Kim et al. 2012, Cole et al. 2014).”

“Uncertain classifications are marked by a colon (:). result in a lower inflow speed, in better agreement with numerical simulations (e.g., Athanassoula 1992).”

“Resonances will thus shape the orbital structure of the galaxy and are therefore critical ingredients to understand the overall evolution (Binney et al. 1991; Athanassoula 1992; Wada & Habe 1995; Englmaier & Shlosman 2000; Stark et al. 2004). c© 0000 RAS ar X iv :1 41 0.”

“So far, we have followed the model of Athanassoula (1992a) exactly.”

“Another indirect method is provided by studying dust lanes, whose curvature is inversely proportional to the bar strength according to the studies of Athanassoula (1992) (probed in Knapen et al. 2002; Comerón et al. 2009; Sánchez-Menguiano et al. 2015), or by 2D decomposition, fitting generalized…”

“…matching gas flow models with observations (Sanders & Tubbs 1980; Lindblad et al. 1996; Weiner et al. 2001) and identifying resonances with certain morphological features such as rings or dust lanes (Buta 1986; Athanassoula 1992; Elmegreen et al. 1992; Moore & Gottesman 1995; Pérez et al. 2012).”

“However non-axisymmetric perturbations such as bars and spiral arms can introduce streaming motions in the gas (e.g., Roberts, Huntley & van Albada 1979; Athanassoula 1992b and references therein).”

“It is easy to understand an anti-correlation of galactocentric radius and fdense: Bars, interactions, and the inner parts of strong spiral arms can drive significant masses of gas towards the inner parts of disks (e.g., Athanassoula 1992; Kormendy & Kennicutt 2004; Sormani et al. 2018).”

“Run S05 was performed in order to check consistency of our results with those of Athanassoula (1992) and Piner et al. (1995).”

“Our basic barred galaxy model in this paper will be the one introduced by Athanassoula (1992a).”

“In many of the galaxies with large-scale bars, these nuclear dust spirals are clearly connected to dust lanes along the leading edge of the bar, similar to what is seen in the hydrodynamic simulations of Athanassoula (1992).”

“These low-fgas simulations have not developed the stellar bars that are relatively common in z < 1 galaxies (and rare at higher redshifts Sheth et al. 2008; Kraljic et al. 2012), which some authors argue can drive significant gas inflows (e.g Athanassoula 1992).”

“This causes a ‘nuclear’ inner Lindblad resonance (nILR), and it is known that trailing spiral shocks are formed around the nILR (Fukuda, Wada, & Habe 1998).”

“Otherwise the shocks curl and start resembling a trailing spiral (Athanassoula 1992b).”

“We used the same implementation of the code as was used by Sormani & Magorrian (2015), slightly modified to implement the recycling law of Athanassoula (1992b).”

“Because of the torques and shocks they generate, bars are very efficient at driving gas toward their centers (assuming there is a sufficient reservoir of material at large radii; see e.g., Athanassoula 1992b; Friedli & Benz 1993, 1995).”