The existence and shapes of dust lanes in galactic bars

“The winding inner part of the principal shocks inside the ILR is made by this process of orbital switching from the x1-orbits that align with the bar axis to the x2-orbits perpendicular to the bar (Athanassoula 1992;Wada 1994; Knapen et al. 1995; Englmaier & Shlosman 2000).”

“…Sorensen et al. 1976; Matsuda, Nelson 1977; Huntley et al. 1978; Matsuda, Isaka 1980; van Albada, Roberts 1981; Schwarz 1984; Matsuda et al. 1987; Athanassoula 1992; Wada, Habe 1992; Friedli, Benz 1993; Wada, Habe 1995; Piner et al. 1995; Heller, Shlosman 1994; Englmaier, Gerhard 1997; Fukuda…”

“At these points, N-body simulations show strong cloud-cloud collisions after gas has efficiently streamed in through the outer bar potential (Regan & Teuben 2003, RodriguezFernandez & Combes 2008, Kim et al. 2011, see also the early gas flow models by Athanassoula 1992).”

“Using this approach Athanassoula (1992) estimated R = 1.2±0.2.”

“Indeed, analytic solutions of the equations of motion and numerical simulations have shown that periodic orbits of stars and gas are aligned perpendicular to the bar in regions beyond corotation and tend to destroy it (Contopoulos & Papayannopoulos 1980; Athanassoula 1992).”

“…Ju n 20 14 Kendall et al. 2003; Saitoh & Wada 2004; Cattaneo et al. 2005), (2) non-axisymmetric perturbations by stellar bars or spiral arms (e.g., Athanassoula 1992), (3) viscous torque on giant molecular clouds (e.g., Fukunaga 1983, 1984b,a), (4) magnetic stress by the magnetic rotational…”

“Athanassoula (1992) showed that gas ridges can reach a galactic center if a largescale bar is very strong.”

“The structure of the dust features—a nearly radial dust lane on the leading side of the bar becoming tangent to a nuclear dust ring—are a clear and clean sign of evolution in action (Athanassoula 1992).”

“The gaseous response to a tumbling bar for a potential with a single ILR was examined by Fukuda, Wada & Habe (1998) via numerical simulations.”

“The gas then flows towards the center and finally set-tles into a ring-like structure closely following the x 2 orbits and thus forming the CMZ-like rings in galaxies (Binney et al. 1991; Athanassoula 1992; Sormani et al. 2015).”

“…that compose theσ-drops can be formed in such nuclear starburst rings, usually due to shock focusing of gas near the locationof one or more inner Lindblad resonances (ILRs; Schwarz 1984; Athanassoula 1992; Knapen et al. 1995, Heller & Shlosman 1996; see also Shlosman 1999, Knapen 2005 for reviews).”

“…simulations of the e†ects of bars in spiral galaxies support the bar-induced fueling scenario (van Albada & Roberts 1981 ; Combes & Gerin 1985 ; Athanassoula 1992 ; Friedli & Benz 1993 ; Shlosman & Noguchi 1993 ; Heller & Shlosman 1994 ; Wada & Habe 1995 ; Fukuda, Wada, & Habe 1998), fueling…”

“Gas Inflow Many barred galaxies show a symmetric pair of dust lanes, connecting the nuclear region with the spiral arms, and associated with shocks in the gas flow (Prendergast 1962; Athanassoula 1992).”

“The dust lanes can be used to trace shocks in the gas flow (Athanassoula 1992) which can be compared to the modelled velocity fields.”

“Several authors studied the dynamics of the gas flowing along the bar (Combes & Gerin 1985; Athanassoula 1992b; Combes & Elmegreen 1993; Fux 1999; Maciejewski et al. 2002; Regan & Teuben 2004; Baba et al. 2010).”

“Therefore, they provide a possible mechanism for fuelling central starbursts and AGN activity (Simkin, Su & Schwarz 1980; Athanassoula 1992; Shlosman, Frank & Begelman 1989; Jogee, Scoville & Kenney 2005; Schawinski et al. 2011; Hicks et al. 2013).”

“be formed through internal, secular evolution (Athanassoula 1992; Wada & Habe 1992, 1995; Friedli & Benz 1993; Heller & Shlosman 1994; Knapen et al. 1995; Sakamoto et al. 1999; Sheth et al. 2003; Regan & Teuben 2004; Kormendy & Kennicutt 2004; Heller et al. 2007a,b; Athanassoula 2008; Fisher et al.…”

“The gas accumulated in the galactic center becomes fuels for the central star formation (Athanassoula 1992).”

“Bars have been proposed as a key mechanism in the dynamical evolution of disc galaxies, for instance, by inducing gas flows (Athanassoula 1992; Friedli 1998).”

“It has been suggested that the noncircular gas motion in the bar region induces strong shocks, large shears, and fast cloud–cloud collisions, which can prevent molecular gas from forming stars (e.g., Tubbs 1982; Athanassoula 1992; Fujimoto et al. 2014a, 2020).”

“…Lindblad Resonance (see Kormendy & Kennicutt 2004; Kormendy 2013; Sellwood 2014; Fanali et al. 2015), while the gas outside is confined to the outer disk (Sanders & Huntley 1976; Shlosman et al. 1989; Athanassoula 1992; Berentzen et al. 1998; Regan & Teuben 2004; Kim et al. 2012; Cole et al. 2014).”

“Bars can affect the gas and star formation properties of their host galaxies (Athanassoula 1992; Oh et al. 2012; Masters et al. 2012).”

“We note that this linear stellar structure is not likely a bar, because the associated H i velocity field does not show the characteristic S-shaped isovelocity contours expected for a bar structure (e.g., Athanassoula 1992).”

“Athanassoula (1992) shows with hydrodynamical models that indeed bars are capable of driving significant masses of gas; this occurs due to shocks on the leading edges of bars that efficiently drive inward flows of gas.”

“The two important ones are the x1 family that runs parallel to the bar major axis, and the x2 family, that runs perpendicular to it (e.g., Athanassoula 1992).”

“There they induce the formation of spiral or ring structures (Prendergast 1983; Athanassoula 1992a,b; Englmaier & Shlosman 2000; Maciejewski 2004; Combes 2004).”

“The ratio of the CR-to-bar radius has been found to lie within the range of 𝑅CR/𝑅bar = 1.2±0.2 (Athanassoula 1992).”

“The narrow dust lanes are strongly curved along the bar, suggesting that the bar is rather weak (Athanassoula 1992).”

“An alternative approach to determine the velocity field is the technique of hydrodynamic simulation of gas flow in a bar potential (e.g. Piner, Stone and Teuben, 1995, Athanassoula, 1992).”

“G A ] 1 7 O ct the disc material (e.g. Sanders & Huntley 1976; Roberts et al. 1979; Athanassoula 1992; Ho et al. 1997; Martinet & Friedli 1997; Ho et al. 1997; Lütticke et al. 2000; Laurikainen et al. 2004; Bureau & Athanassoula 2005; Jogee et al. 2005; Kormendy 2013; Cheung et al. 2013; Fanali et…”

“Article number, page 4 of 23 found by Athanassoula (1992b), which is in fairly good agreement with recent calculations (e.g., Aguerri et al. 2015).”

“The x1 (bar) orbits are extended along the major axis of the bar whereas the x2 (antibar) orbits are perpendicular to the bar major axis (e.g., Contopoulos & Mertzanides 1977; Athanassoula 1992a,b; Binney & Tremaine 2008).”

“The construction of a detailed dynamical model would make it possible to conclude if the low luminosity bar of NGC 1566 has enough gravitational potential to generate those non-circular motions (Athanassoula 1992; Piner et al. 1995).”

“Some studies using both simulations and observations have suggested that some star formation may occur along the bar as soon as the bar forms and induces shocks in the gas content in the interface between the bar and the disc (see Athanassoula, 1992; Phillips, 1996; Sheth et al, 2002).”

“This fact seems to correlate with the presence of bars in early-type spiral galaxies (Combes & Gerin 1985; Athanassoula 1992).”

“Interpretation Spiral arms and bars can cause gas mass surface density contrast ratios (between arm and interarm of dust lane and interÈdust lane) of greater than a factor of a few in the plane of the galaxy (e.g., Hausman & Roberts 1984 ; Athanassoula 1992).”

“The gas in the disk is likely to steam along the molecular bar, pile up at the ILRs, and trigger star formation (Athanassoula 1992; Roming et al. 1999).”

“While this may be a consequence of the limited spatial resolution of our data, we stress that a natural explanation for the central deviation from the global rotation could lie in the weak break in axisymmetry that was reported by B95 (Athanassoula 1992).”

“Stronger bars are predicted to supply gas towards the galaxy centres at a higher rate (e.g. Athanassoula 1992; Regan & Teuben 2004; Kim & Stone 2012).”

“In addition, simulations prove that the efficiency of driving gas depends on bar strength, i.e., stronger bars are able to transport more material at a faster rate than weak bars (e.g., Athanassoula 1992; Regan & Teuben 2004).”

“3 we show that the size of the CMZ shrinks with lower Υ, due to a decreasing central mass (e.g. Athanassoula 1992; Regan & Teuben 2003; Li et al. 2015, 2017).”

“This can be regarded as a signature of a shear shock due to gas infall on the inner side of the bar (see numerical models e.g. by Athanassoula 1992).”

“Athanassoula (1992) shows that these shocks are intimately linked to the dust lanes which appear in many barred galaxies.”

“Bar-A Bar-B Arm1-A Arm1-B Arm1-C Bar-end-A Bar-end-B SFEGMC (Gyr−1) < 0.04 0.17 ± 0.04 1.97 ± 0.36 1.55 ± 0.24 1.52 ± 0.20 0.51 ± 0.11 0.44 ± 0.06 diffuse gases (e.g. Tubbs 1982; Athanassoula 1992; Reynaud & Downes 1998).”

“Due to their non-axisymmetry, bars can cause the gas to flow inwards (e.g., Athanassoula 1992; Regan et al. 1999; Sheth et al. 2000), thus enhancing star formation in the central regions of their host galaxies (Sérsic & Pastoriza 1967; Hawarden et al. 1986; Ho et al. 1997; Sheth et al. 2005;…”

“The aim of the present Letter is to improve the statistics compared to the latter study, and to test definitively the prediction from Athanassoula (1992).”

“We use a grid-based, Eulerian code based on the second-order c© 0000 RAS, MNRAS 000, 000–000 flux-splitting scheme developed by van Albada et al. (1982) and later used by Athanassoula (1992), Weiner & Sellwood (1999) and others to study gas dynamics in bar potentials.”

“On larger scales, galactic bars can be very effectivein extracting angular momentum from the gas in galaxies and driving it toward the center (Athanassoula 1992, 1994; Kenney 1994; Kennicutt 1994; Sellwood and Shen 2004).”

“For example, as stronger bars have more elongated isophotes, the maximum ellipticity of these isophotes has been used to estimate bar strength (Athanassoula 1992b; Laurikainen & Salo 2002; Erwin 2004).”

“They are particularly evident in barred galaxies, where they are believed to be created by bar-driven inflow (e.g., Athanassoula, 1992; Heller & Shlosman, 1994).”

“Stellar bars in disc galaxies can form either spontaneously, as a result of the bar instability (e.g. Hohl 1971; Sellwood 1980; Athanassoula 1992; Berentzen et al. 1998), or following interactions with other galaxies (e.g. Toomre & Toomre 1972; Gerin, Combes & Athanassoula 1990; Berentzen et al.…”

“…observational and theoretical studies (e.g. Jorsater, Lindblad & Boksenberg 1984; Teuben, Sanders, Atherton & van Albada 1986; Sandage et al. 1988; Athanassoula 1992; Piner, Stone & Teuben 1995; Kim et al. 2012; Sormani, Binney & Magorrian 2015) in barred galaxies gas accumulates along two well…”

“Instead, our models have a stream of gas with prescribed properties entering though the domain boundaries, mimicking gas inflows along the dust lanes in global simulations (e.g., Athanassoula 1992; Kim et al. 2011b, 2012b; Sormani et al. 2015; Shin et al. 2017).”

“The molecular gas moves along the straight ridges at the leading sides of the bar, as theoretical simulations have predicted (e.g., Athanassoula 1992b).”

“%) of the available barred galaxies is explained as due to the non-circular (e.g. Athanassoula 1992) and off-plane (e.g. Friedli & Benz 1993) motions induced on the gaseous component by the tumbling triaxial potential of the bar.”

“…physical conditions within bars, which are sites of for example strong shear, shocks and non-circular velocities (e.g. Pence & Blackman 1984; Athanassoula 1992; Reynaud & Downes 1998; Zurita et al. 2004), and significant magnetic–field strength (e.g. Beck 2002), make them excellent…”

“The strong curvature of the dust lanes is qualitatively consistent with expectations for a weak bar (Athanassoula 1992).”

“Simulations predict a dependency between the gas inflow rate and the bar strength, with stronger bars supplying gas towards the centre at a higher rate (Athanassoula 1992; Regan & Teuben 2004).”

“Theoretical work (e.g. Athanassoula 1992; Hopkins & ?”

“These Cepheids are unique in that they allow us to probe the transition between the inner Disk and the central regions of the Galaxy along the minor axis of the central Bar, where they are expected to be be less affected by its dynamical influences.”

“The gas flow then transition from the gas lane to a new orbit, producing a ring and/or central spiral structures around the nucleus of the galaxy (Athanassoula 1992a,b; Piner et al. 1995).”

“The orbiting gas loses angular momentum at the dust-lane shocks and falls toward the galactic center (Athanassoula 1992).”

“…orientations 3The corotation radius is the radius at which the rotation speed of the studied disk equals the orbital speed of the companion. response is found in barred galaxies, where the disk symmetry is broken about the same way by the barred pattern (Combes & Gerin, 1985; Athanassoula, 1992).”

“Several studies (e.g., Athanassoula 1992; Combes & Elmegreen 1993; Sempere et al. 1995) have shown that the ratio of the bar corotation radius to the bar semimajor axis length is in the range 1–1.5.”

“There have been many previous studies of bar-driven nuclear spirals starting with Sanders & Huntley (1976), Roberts et al. (1979), Athanassoula (1992), Piner et al. (1995), and others.”

“This configuration would be however inconsistent with the dynamical studies predicting that the barred gravitational potential produces a family of closed x2 orbits perpendicular to the bar (e.g. Binney et al. 1991; Athanassoula 1992).”

“…by Schwarz (1981, 1984) and Habe & Ikeuchi (1985), smooth Ñuids simulations by Sanders & Huntley (1976), van Albada (1985), Mulder & Liem (1986), and Athanassoula (1992), and smoothed particle hydrodynamic (SPH) simulations by Wada & Habe (1992), Friedli & Benz 242 (1992), and Fux & Friedli (1996).”