Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userFabry-Perot Absorption-Line Spectroscopy of NGC 7079: Kinematics and Bar Pattern Speed
145
0
0.0
(
0
)
Added by
Victor P. Debattista
Publication date
2004
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
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 $Omega_p$.
rate research
Read More
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.
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 show that significant water wave amplification is obtained in a water resonator consisting of two spatially separated patches of small-amplitude sinusoidal corrugations on an otherwise flat seabed. The corrugations reflect the incident waves according to the so-called Bragg reflection mechanism, and the distance between the two sets controls whether the trapped reflected waves experience constructive or destructive interference within the resonator. The resulting amplification or suppression is enhanced with increasing number of ripples, and is most effective for specific resonator lengths and at the Bragg frequency, which is determined by the corrugation period. Our analysis draws on the analogous mechanism that occurs between two partially reflecting mirrors in optics, a phenomenon named after its discoverers Charles Fabry and Alfred Perot.
Resistance oscillations in electronic Fabry-Perot interferometers near fractional quantum Hall (FQH) filling factors 1/3, 2/3, 4/3 and 5/3 in the constrictions are compared to corresponding oscillations near integer quantum Hall (IQH) filling factors in the constrictions, appearing in the same devices and at the same gate voltages. Two-dimensional plots of resistance versus gate voltage and magnetic field indicate that all oscillations are Coulomb dominated. Applying a Coulomb charging model yields an effective tunneling charge e* approx e/3 for all FQH constrictions and e* approx e for IQH constrictions. Surprisingly, we find a common characteristic temperature for FQH oscillations and a different common characteristic temperature for IQH oscillations.
We show how to analyze the motion of very low dissipation suspended mirrors in a Fabry-Perot. The very precise measurements of the mirrors motion can be determined, also in the presence of a disturbing noise, by means of the sudden reflectivity changes in special points of the mirrors positions. When the mirrors cross such positions, the effective opto-mechanical potential that arises in the device is (roughly) at a maximum. We show that the motion cross such potential maxima is not only confused by the presence of noise, but also favoured by noise itself that induces hoppings. Thus, the measurements of the times at which the crossings occur can be exploited to identify the properties of the applied signal. We also show how to circumvent the difficulty of the extremely long transient that occur in the system analyzing the escape average time with two different methods: a direct sample average and the indirect estimate from the tail distribution. Numerical simulations and physical insight suggest that the indirect estimate, through the analysis of the distribution tails with an appropriated cut off is robust against the disturbances that arise from the presence of transient dynamics.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
