Timeline for What is the unit of the correlation function between logarithmically rebinned galaxy spectrum and stellar template spectrum?
Current License: CC BY-SA 4.0
14 events
| when toggle format | what | by | license | comment | |
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| May 30, 2023 at 7:26 | vote | accept | trynerror | ||
| May 29, 2023 at 7:18 | history | edited | ProfRob | CC BY-SA 4.0 |
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| May 29, 2023 at 7:04 | comment | added | trynerror | Neper ($1 NP$) is just the unit convention when using the natural logarithm. When variable $a$ has unit $1 b$, then the natural logarithm $\ln a$ has unit $1 Np/b$ . | |
| May 29, 2023 at 7:02 | comment | added | trynerror | I don't know what variables you are refering to exactly, I gave the formulas and units of all variables I use in these brackets [] in the question. Could you please explain why the unit of pixels is fractions of the speed of light, when binned in equal steps of $\ln{\lambda}$? | |
| May 27, 2023 at 20:23 | comment | added | ProfRob | @trynerror please define all your notation and abbreviations in your question. I can't understand any of this. | |
| May 26, 2023 at 18:53 | comment | added | trynerror | If $[\lambda] = 1 Å$ and $x = \ln{\lambda}$ then $[x]=1 Np/Å,$ (en.wikipedia.org/wiki/Neper). If I read your last comment correctly x (the pixels) have unit $[x] = [1/c] = 1 s/km$ for $[c] = 1 km/s$ I just would like all the units written out for the equations I used in the question. | |
| May 26, 2023 at 14:59 | comment | added | ProfRob | @trynerror I don't know what Np per Angstrom means. If you have binned in equal steps of $\ln \lambda$ then the pixels have units of fractions of the speed of light. | |
| May 26, 2023 at 14:49 | comment | added | trynerror | So if z is the lag in pixels, and 1 pixel has the unit 1 Np/Å, then the velocity shift would be of units 1 Np/Å * km/s ? | |
| May 26, 2023 at 14:37 | comment | added | trynerror | When I write $K_{S, G}(z)= \int dx G(x+z)S(x)$, then the units of x and z should be the same formally ? I understand your answer and it makes sense, I guess the remaining doubt is more about this formula. | |
| May 26, 2023 at 14:24 | history | edited | ProfRob | CC BY-SA 4.0 |
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| May 26, 2023 at 14:22 | comment | added | ProfRob | @trynerror I don;t understand your comment. The x-axes of both spectrum and template need to be the same. The cross correlation is a function of $z$, which is the lag in pixels. | |
| May 26, 2023 at 13:47 | comment | added | trynerror | assuming that the unit i gave for x is correct of course. | |
| May 26, 2023 at 13:47 | comment | added | trynerror | Makes sense, but what do I need to change in the formula to make it consistent. Because looking at the formula that I gave for the cross-correlation function the function argument of the galaxy spectrum$(x+z)$ inside the integral needs to have the same units. | |
| May 26, 2023 at 13:41 | history | answered | ProfRob | CC BY-SA 4.0 |