PROMOS: PROper MOtion Software
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PROMOS: PROper MOtion Software

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  • 1. PRO-MOTIONS: PROper MOTION Software John C. Wherry , Raghvendra Sahai 1 2 Austin Peay State University, Clarksville, TN, USA 1 2 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA Introduction Results: Red Rectangle Results: Egg NebulaWe report on the development of a software tool The object in figures 4 and 5 is the(PRO-MOTIONS) to determine the proper motions of PPN, CRL 2688 (Egg Nebula).material in expanding nebulae. This tool registers and Figure 4 shows you the propercompares images of an object from two epochs. C motions of each feature. PM-neb was measured to be 14.6 mas/yr,PRO-MOTIONS is built with the Interactive Data which compares reasonably wellLanguage (IDL) programming environment with with Ueta et als value (17.1certain subroutines developed in C++. IDL provides a mas/yr).stable platform on which to develop widget-stylesoftware applications and bind different code bases A The proper motions of thetogether. C++ offers a programming environment for symmetric pairs lie in the rangefast processing of data. 10.3 mas/yr – 12.8 mas/yr with a mean value of 11.3 ± 0.5 mas/yr.We have three main objectives while developing We use this mean value toPRO-MOTIONS: Figure 2: Red Rectangle Selected features in the Figure 3: Selected Features Two examples of selected features calculate the age and tangential Red Rectangle with PM-neb subtracted out. Red used to calculate PM-neb. We pick features that are centrally Figure 4: Egg Nebula Selected symmetric features Figure 5: Selected Inner Features Selected features expansion velocity of the nebula. with no symmetric pairs. Proper motion vectors vectors show the proper motion of the features. located in our box and have paddings of non-bright pixels. used in calculation of PM-neb. Red vectors represent Build an application that can easily and efficiently proper motions of individual features. obtained by subtracting out PM-neb.register astrophysical objects to a common frame of The proper motions of lower Age = 1,400 yr at radius of quality features not used inreference between two epochs and calculate their PM-exp = 9.35 mas/yr 13” (i.e., 9,100 AU at D = Vtang = 31 km/s (D/0.7 kpc) calculating PM-neb (i.e., Non-proper motions. 0.7 kpc) E Pairs) lies in the range 6.9 to 13.9Create a complete, integrated software system for mas/yr with a mean value of 11.0 ±measuring proper motions. 2.4 mas/yr. The first object we studied was the PPN (pre-planetary nebula), the Red Rectangle (Cohen et al. 2004). Figure 2 shows the proper motions of each feature. PM-neb was Construct a completely platform independent measured to be 8.9 mas/yr.software package. B PM-exp = 11.3 mas/yr The proper motions of the symmetric pairs (i.e., PM-exp) lie in the range 8.6 to 10.1These objectives have led to the development of a mas/yr with a mean value of 9.3 ± 0.5 mas/yr. We use the mean from symmetric pairssoftware package that is both robust and agile to code Age = 2,000 yr at radius to calculate the age and tangential expansion velocity of the nebula.enhancements. of 22.5” (i.e., 22,500 AU The proper motions of lower quality features not used in calculating PM-neb (i.e., Non- at D = 1 kpc) Figure 6: Selected Features Two examples of selectedPROMOTIONS should find wide applicability in Pairs [features that have no radially symmetric pair]) lies in the range 5.6 to 11.3 mas/ features used to calculate PM-neb. Just as with the Red Figure 7: Selected Outer Features Selected featuresmeasuring proper motions in astrophysical objects yr with a mean value of 8.8 ± 2.1 mas/yr. Rectangle, we pick features that are centrally located in That are located further away from the nebular center.such as the expanding outflows/jets commonly seen our box and have paddings of non-bright pixels. Feature Vtang = 54 km/s (D/1 kpc) The naming scheme here is not the same as in fig. 5.around young and dying stars (e.g., Sahai et al. names as in figure 4. We assume a distance of 0.7 kpc (Cohen et al. 2004) to this object.2007). A major uncertainty in calculating the tangential expansion velocity is that its derived value is proportional to the distance to the object. In the above calculation, we take the commonly assumed value of the distance (1 kpc). In the outer region, the outflow is known to be spherical with an expansion velocity of about 20 km/s. Therefore, a smaller Software Methods value of the distance, such as that inferred by Ueta et al (420 pc), is likely to be correct. PRO-MOTIONS allows us to first orient and register images to Our argument for a smaller distance is quite robust because, unlike Ueta et al, it does not require a knowledge of the a common frame of reference and pixel scale, using field stars inclination angle of the bipolar outflow (which dominates in the inner region). in each of the images. We use a bicubic spline interpolation routine written in C++ developed by Dwight Moody (JPL) to The features we are analyzing are at a much further radial distance from the central star than the features analyzed by correctly carry out this process. Stars that are designated as Ueta et al. (2005). Our symmetric pairs lie between 8” and 14” and the features analyzed by Ueta et al. lie between 1” outliers are flagged and not used in calculations. and 7” away from the central star. We then cross-correlate specific morphological features in For the inner region (Fig. 5: c,d,e,f,g,h), which has also been analyzed by Ueta et al., our calculated value of the order to determine their proper motions, which consist of the average proper motion (9.3 mas/yr) is somewhat lower than Ueta et als value (14.3 mas/yr). proper motion of the nebula as a whole (PM-neb), and expansion motions of the features relative to the center. We use routines from the IDL Astronomy Users Library to help with these calculations.1 Summary & Work In Progress PRO-MOTIONS is a handy tool for calculating the age of a nebula because expansion proper motions are the only If the central star is not visible (quite common in bipolar direct way of measuring this age. Furthermore, these do not require knowledge of the distance to the object (which nebulae with dense dusty waists), we assume point-symmetric are hard to determine). The age of a feature is given by the radial offset of that feature from the center divided by the expansion, and use the average motion of high-quality proper motion per unit time. The total nebular age can then be estimated by proportionately extrapolating to the full symmetric pairs of features on opposite sides of the nebular size of the nebula. center to compute PM-neb, which is then subtracted out to determine the individual movements of these and additional PRO-MOTIONS allows us to measure the proper motion of features in nebulae. This proper motion is one of the two features relative to the nebular center. orthogonal components needed to calculate the 3D radial expansion of the feature (the other component being the velocity calculated by observing the Doppler shift of an emission line from that feature). These two vectors combined Our main interface (Fig. 1) shows you the basic design of our yield the radial expansion of the feature in 3D. software package. PRO-MOTIONS is still under development and a number of improvements are currently being implemented. For Care has been taken to implement features that allow users to example, making PRO-MOTIONS cross-platform and adding geometric tools that allow us to estimate the center of change contrasts, rotate, and annotate images, among other the nebula based on symmetric features such as circular arcs and searchlight beams in the nebula. Further, spatially things. This simplifies the process of producing a finished extended features are not well handled by the cross-correlation routine for determining proper motions, we intend to product. include software to make and compare radial and angular intensity cuts which are more suited to the analysis of such features. For example, after proper motions have been computed, the user can produce publication-quality plots of the proper motion Acknowledgements: This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, and was vectors superimposed on the nebular image (Fig. 2-7). sponsored by the Undergraduate Student Research Program (USRP) and the National Aeronautics and Space Administration. Figure 1: PRO-MOTIONS Graphical user interface (GUI) for Image Registration section of the We also want to thank Dwight Moody (JPL) for contributing his code for the bicubic spline interpolation routine. application. The object displayed is the PPN (pre-planetary nebula), IRAS22036. PRO-MOTIONS All error handling is dealt with in a “loopback” format. If an is very dynamic in that users can interactively update and change the color tables, contrast, and error occurs during the running of PRO-MOTIONS, the state References brightness of the images displayed. All of the analysis results are displayed on the screen for of the program is reverted back to the previous state before - Balick, B., Adam, F., 2002. “Shapes and Shaping of Planetary Nebulae” Annual Review of Astronomy and Astrophysics,Vol. 40, p. 439-486. convenience of the user. the error occurred. This allows PRO-MOTIONS to keep - Cohen, M., Van Winckel, H., Bond, H.~E., Gull, T.~R., 2004. “Hubble Space Telescope Imaging of HD 44179. The Red Rectangle” Astronomical Journal, running when errors occur and allows the user to continue 127, 2362. with his/her analysis without loss of previous work. - Sahai, R., Morris, M., Sanchez Contreras, C., Claussen, M., 2007. “Preplanetary Nebulae: A Hubble Space Telescope Imaging Survey and a New ´ 1The IDL Astronomy Users Library is publicly available through http://idlastro.gsfc.nasa.gov/. Morphological Classification System” Astronomical Journal, 134, 2200. - Ueta, T., Murakawa, K., Mexiner, M., 2005. “Proper-Motion Measurements of the Cygnus Egg Nebula” ApJ, 641, 1113.