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Rotation Velocity Curve Measurement of SDSS-IV Manga Galaxies

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Rotation Velocity Curve Measurement of SDSS-IV Manga Galaxies Rotation Velocity Curve Measurement of SDSS-IV MaNGA Galaxies 6th Survey Science Group Workshop 2017 June 30th, Ulleung Dae-A Resort Haeun Chung (SNU/KIAS) and Changbom Park (KIAS) Galaxy Rotation Curve Vera Rubin found flat rotation curve of M31 Corbelli and Salucci (1999) Rubin and Kent (1970) Dark Matter Star Gas Mass distribution of baryons can not explain this! 2017-07-03 6th Survey Science Group Workshop 2 MaNGA: Mapping Nearby Galaxies at APO . Multi-Integral Field Unit (Multi-IFUs) . 17 IFUs on 3° diameter plate – IFU diameters from 12” to 32” – Galaxy radius up to 1.5 – 2.5 Re . SDSS BOSS Spectrograph – 3600-10300Å, R~2000 . Project duration: 6 years – Launched on 2014 July 1 – Half of SDSS-IV dark time . Aim to observe ~ 10,000 galaxies . Data Release (July 2016) – SDSS DR13 – 1,390 MaNGA Galaxies (observed by June 2015) 2017-07-03 6th Survey Science Group Workshop 3 MaNGA: Mapping Nearby Galaxies at APO 2017-07-03 6th Survey Science Group Workshop 4 ~1,390 MaNGA Galaxies from SDSS DR13 Purpose of this Study . MaNGA is an excellent survey to study kinematics of nearby galaxies. – Especially stellar kinematics. Measure Rotation Curve from all MaNGA Galaxies, automatically! 2017-07-03 6th Survey Science Group Workshop 7 Galaxy Rotation Curve 휽 휽 ( , ) , = + ×′ sin′ × cos ↔ = sin × cos − First, we need to measure 2D line of sight velocity (VLOS) of galaxies 2017-07-03 6th Survey Science Group Workshop 8 2D Velocity Map . We use pPXF to measure LOSVD of each spaxel. – Penalized Pixel-Fitting (pPXF) is a SED model fitting code developed by Michele Cappellari (Cappellari+04) . We use Miles stellar libraries - Solar Metallicity, 2 ages . 1,390 All DR13 MaNGA galaxies: 400-2700 specs/IFU . Total 2.2M specs to measure LOSVD 3D Cube Data Run pPXF - Velocity - Velocity dispersion - High order kinematics - Steller population Cappellari+17 2017-07-03 6th Survey Science Group Workshop 9 2D Velocity Map Now we have 2D Vel Map of all DR13 1,390 MaNGA Galaxies 2017-07-03 6th Survey Science Group Workshop 10 Galaxy Rotation Curve Measurement . To measure RC, we need to know , , inclination angle , position angle . All MaNGA galaxies are observed before. So we already know above parameters. . Done…? 2017-07-03 6th Survey Science Group Workshop 11 Galaxy Rotation Curve Measurement . Incorrect photometric PA / Inclination Angle 2017-07-03 6th Survey Science Group Workshop 12 Galaxy Rotation Curve Measurement . Off center cases . We can not just use SDSS image data. we need to obtain Incl, PA, and center from 2D VelMap!! 2017-07-03 6th Survey Science Group Workshop 13 Galaxy Rotation Curve Measurement . How to measure geometrical parameters from 2D Vel Map? = + × sin × cos . If we have a good V(r), we can fit a 2D velocity model on to the data to get the geometrical parameters. Fortunately, we have a simple function which well approximate an actual RC. – Hyperbolic tangent function. = × tanh(r/R ) c R c Galaxy Rotation Curve Measurement . 2D model velocity map with different inclination angle / Rc Inclination Angle R c Galaxy Rotation Curve Measurement . We need one more step – We need a proper mask! . Now we have proper masks for model fitting. 2017-07-03 6th Survey Science Group Workshop 16 2D Velocity Model Fitting . We fit 7 parameters simultaneously + Xcent , Ycent = + × tanh(r/ ) × sin × cos . Due to limitation of MPFIT, fitting result is very sensitive to the initial parameters. . Two solutions – Do Monte Carlo – Provide good initial value . Fit the model with good initial value. Use known SDSS photometric data. Use photometric data during mask generation . First fit on smoothed 2D vel map, second fit on original 2D vel map. -> Smoothed vel map image 2017-07-03 6th Survey Science Group Workshop 17 Fitting Results 2D Velocity Map Results . Success ratio: – Out of 1,390 MaNGA galaxies: – 996 galaxies shows good results – 71.6% . We are working on increasing success rate 2017-07-03 6th Survey Science Group Workshop 22 Limitation of MaNGA 3D Cube . MaNGA 3D Cube is quite blurred, due to IFU sampling size and seeing. SDSS Camera Pixel Size SDSS gri 2” 0.4” MaNGA gri MaNGA fiber size 2017-07-03 6th Survey Science Group Workshop 23 Limitation of MaNGA 3D Cube . Since size of PSF (point spread function) is large, (~2.5” in FWHM) it would affect to the shape of the measured 2D velocity map. Convolution Original Galaxy MaNGA PSF Observed Galaxy 2017-07-03 6th Survey Science Group Workshop 24 Deconvolution . If we know the PSF which made observed galaxy, we can (mathematically, theoretically) reverse the convolution process and make original galaxy! Deconvolution Observed Galaxy MaNGA PSF Original Galaxy 2017-07-03 6th Survey Science Group Workshop 25 3D Cube Deconvolution y Deconvolution with known Gaussian PSF x Original 2D Image 2D Image Deconvolved MaNGA 3DCube @each wavelength After deconvolution MaNGA 3DCube 3D Cube Deconvolution . MaNGA provides FWHM at 4 wavelengths (griz) – About 2.5” . Deconvolution algorithm – Simple inversion – Lucy-Richardson (Poisson max likelihood) – Frieden (Friden max entrophy) Original – Gaussian (Gaussian max likelihood) MaNGA gri – Jansson-van Cittert . Noise? – From original 3D cube. (1st order approximation) Fitting Results Fitting Results Compare Before / After Deconvolution 2017-07-03 6th Survey Science Group Workshop 30 Compare Before / After Deconvolution 2017-07-03 6th Survey Science Group Workshop 31 Inclination Degeneracy 2017-07-03 6th Survey Science Group Workshop 32 Summary . We measure velocity rotation curves from original / deconvolved MaNGA 3D Cubes. – Measure 2D VLOS map from 3D Cube – Generate proper mask – Fit tanh 2D VLOS map to get geometrical parameters . Deconvolved 3D Cube show small scale structures as well as true rotation curve. We work on developing science cases using these data, including analysis on abnormal cases. 2017-07-03 6th Survey Science Group Workshop 33.
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