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Register a new userOn the bar pattern speed determination of NGC 3367
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An important dynamic parameter of barred galaxies is the bar pattern speed. Among several methods that are used for the determination of the pattern speed the Tremaine-Weinberg method has the advantage of model independency and accuracy. In this work we apply the method to a simulated bar including gas dynamics and study the effect of 2D spectroscopy data quality on robustness of the method. We added a white noise and a Gaussian random field to the data and measured the corresponding errors in the pattern speed. We found that a signal to noise ratio in surface density ~5 introduces errors of ~20% for the Gaussian noise, while for the white noise the corresponding errors reach ~50%. At the same time the velocity field is less sensitive to contamination. On the basis of the performed study we applied the method to the NGC 3367 spiral galaxy using H{alpha} Fabry-Perot interferometry data. We found for the pattern speed 43 pm 6 km/s/kpc for this galaxy.
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We present the first galactic-scale model of the gas dynamics of the prototype barred Seyfert 1 galaxy NGC1097. We use large scale FaNTOmM Fabry-Perot interferometric data covering the entire galactic disc and combine the distribution and kinematics maps with high resolution two-dimensional spectroscopy from the Gemini telescope. We build a dynamical model for the gravitational potential by applying the analytic solution to the equations of motion, within the epicyclic approximation. Our model reproduces all the significant kinematic and structural signatures of this galaxy. We find that the primary bar is 7.9+/-0.6 kpc long and has a pattern speed of 36 +/- 2 km s^-1 kpc^-1. This places the corotation radius at 8.6 +/-0.5 kpc, the outer Lindblad resonance at 14.9+/-0.9 kpc and two inner Lindblad resonances at 60+/-5 pc and 2.9+/-0.1 kpc. These derivations lead to a ratio of the corotation radius over bar length of 1.0--1.2, which is in agreement with the predictions of simulations for fast galaxy bars. Our model presents evidence that the circumnuclear ring in this galaxy is not located near any of the resonance radii in this galaxy. The ring might have once formed at the outer inner Lindblad resonance radius, and it has been migrating inward, toward the centre of the galactic gravitational potential.
We compare distance resolved, absolute proper motions in the Milky Way bar/bulge region to a grid of made-to-measure dynamical models with well defined pattern speeds. The data are obtained by combining the relative VVV Infrared Astrometric Catalog v1 proper motions with the Gaia DR2 absolute reference frame. We undertake a comprehensive analysis of the various errors in our comparison, from both the data and the models, and allow for additional, unknown, contributions by using an outlier-tolerant likelihood function to evaluate the best fitting model. We quantify systematic effects such as the region of data included in the comparison, with or without possible overlap from spiral arms, and the choice of synthetic luminosity function and bar angle used to predict the data from the models. Resulting variations in the best-fit parameters are included in the final error budget. We measure the bar pattern speed to be Omega_b=35.4+-0.9 km/s/kpc and the azimuthal solar velocity to be V_phi_sun= 251.4+-1.7 km/s. These values, when combined with recent measurements of the Galactic rotation curve, yield the distance of corotation, 6.3 < R_(CR) [kpc] < 6.8, the outer Lindblad resonance (OLR), 10.5 < R_(OLR) [kpc] < 11.5, and the higher order, m=4, OLR, 8.5 < R_(OLR_4) [kpc] < 9.0. The measured low pattern speed provides strong evidence for the long-slow bar scenario.
NGC3367 is a nearby isolated active galaxy that shows a radio jet, a strong bar and evidence of lopsidedness. We present a quantitative analysis of the stellar and gaseous structure of the galaxy disk and a search for evidence of recent interaction based on new UBVRI Halpha and JHK images and on archival Halpha Fabry-Perot and HI VLA data. From a coupled 1D/2D GALFIT bulge/bar/disk decomposition an (B/D ~ 0.07-0.1) exponential pseudobulge is inferred in all the observed bands. A NIR estimate of the bar strength <Q_T{max}(R)> = 0.44 places NGC 3367 bar among the strongest ones. The asymmetry properties were studied using (1) optical and NIR CAS indexes (2) the stellar (NIR) and gaseous (Halpha, HI) A_1 Fourier mode amplitudes and (3) the HI integrated profile and HI mean intensity distribution. While the average stellar component shows asymmetry values close to the average found in the Local Universe for isolated galaxies, the young stellar component and gas values are largely decoupled showing significantly larger A_1 mode amplitudes suggesting that the gas has been recently perturbed. Our search for (1) faint stellar structures in the outer regions (up to u_R ~ 26 mag arcsec^{-2}), (2) (Halpha) star-forming satellite galaxies and (3) regions with different colors (stellar populations) along the disk all failed. Such an absence is interpreted using recent numerical simulations to constrain a tidal event with an LMC like galaxy to some dynamical times in the past or to a current very low mass, gas rich accretion. We conclude that a cold accretion mode (gas and small/dark galaxies) may be responsible of the nuclear activity and peculiar (young stars and gas) morphology regardless of the highly isolated environment. Black hole growth in bulgeless galaxies may be triggered by cosmic smooth mass accretion.
Gas morphology and kinematics in the Milky Way contain key information for understanding the formation and evolution of our Galaxy. We present a high resolution hydrodynamical simulation based on a realistic barred Milky Way potential constrained by recent observations. Our model can reproduce most features in the observed longitude-velocity diagram, including the Central Molecular Zone, the Near and Far 3-kpc arms, the Molecular Ring, and the spiral arm tangents. It can also explain the non-circular motions of masers obtained by the recent BeSSeL2 survey. The central gas kinematics are consistent with a mass of $6.9times10^8; {rm M}_{odot}$ in the Nuclear Stellar Disk. Our model predicts the formation of an elliptical gaseous ring surrounding the bar, which is composed of the 3-kpc arms, Norma arm, and the bar-spiral interfaces. This ring is similar to those inner rings in some Milky Way analogs with a boxy/peanut-shaped bulge. The kinematics of gas near the solar neighbourhood are governed by the Local arm, which is induced by the four major stellar spiral arms. The bar pattern speed constrained by our gas model is $37.5-40; {rm km};{rm s}^{-1};{rm kpc}^{-1}$, corresponding to a corotation radius of $R_{rm CR}=6.0-6.4;{rm kpc}$. The rotation curve of our model rises gently within the central $sim5;{rm kpc}$, which is significantly less steep than those predicted by modern zoom-in cosmological simulations such as Auriga.
We present Fabry-Perot absorption-line spectroscopy of the SB0 galaxy NGC 7079. This is the first use of Fabry-Perot techniques to measure the two-dimensional stellar kinematics of an early-type disk galaxy. We scan the infrared CaII line using the Rutgers Fabry-Perot (RFP), to obtain kinematic data extending to $I$-band surface brightness $mu_I simeq 21$ mag./arcsec^-2, in a field of radius $sim 40arcsec$. The kinematic data, consisting of line-of-sight velocities and velocity dispersions, are in good agreement with data obtained along the major axis of the disk with standard slit spectroscopy. Comparison of the exposure times required for slit and RFP spectroscopy to reach the same limiting magnitude shows that the RFP is significantly more efficient for mapping absorption-line galaxy kinematics. We use the velocity data, together with our own deep broad-band photometry,to measure the bar pattern speed, $Omega_p$, of NGC 7079 with the model-independent Tremaine-Weinberg (TW) method. We find $Omega_p = 8.4 pm 0.2$ km/s/arcsec; this is the best-constrained pattern speed ever measured for a bar using the TW method. From the rotation curve, corrected for asymmetric drift, we calculate the co-rotation radius and find that the bar ends just inside this radius. The two-dimensional character of these data allow us to show that the TW method is sensitive to errors in the position angle (PA) of the disk. For example, a PA error of $2degrees$ can give errors $sim pm 25%$ in $Omega_p$.
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