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2

I think the velocity scale is calculated something like this: $$v_r = c\left( \frac{\lambda - \lambda_0}{\lambda_0}\right),$$ where $\lambda$ is the observed wavelength and $\lambda_0$ is wavelength of the Mg II line, corrected for the redshift of the quasar ($z=0.868)$ it is observed towards. The confusing thing is, for Fig.~3 in the cited paper, that the ...


0

It takes a spot "bump" half the rotation period to traverse from the blue side of the line profile to the red. You can see that the bump has maybe moved across 20% of the profile in one night, so the rotation period would be estimated as $\sim 10$ days. Looking up the period of Sigma Gem - it is 19.6 days. So my method is not very accurate by eye, ...


2

One thing you might try doing is to use the SkyServer Navigate interface to see if the object was imaged by SDSS. Enter the name in the "name" box in the upper left and then click on the "Resolve" button. If an image with the galaxy shows up, click on the "Object with spectra" checkbox in the "Drawing options" panel on ...


5

Okay, well, calcium is just an easily recognizable spectral feature, so I guess that's why they used it. The y-axis shows the relative intensity. I am assuming this is a spectrum that is normalized or scaled down so that the highest value of the intensity is 1, but this is not so important. The laboratory wavelengths of the absorption lines are shown in red ...


1

The information you need to recreate the wavelength array is in the World Coordinate System (WCS) of the header, specifically: CRPIX1 = 1.00 CRVAL1 = 3500.0000 / central wavelength of first pixel CDELT1 = 0.900000 / linear dispersion (Angstrom/pixel) which lists the starting/reference pixel of the wavelength array (...


3

I think I can sort of answer your first/second question. It's a bit hard to guess what your background is, but I hope you have seen or derived somewhere that the $a_{lm}$ coefficients can be written as $$\oint \Theta(\hat{x}) Y_{lm}^*(\hat{x}) d\hat{x}$$ where $\Theta$ is the temperature fluctuation (as seen in the CMB) and $Y_{lm}^*$ is (the complex ...


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