Questions tagged [flux]

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Astronomical data bases express spectra in flux density, e.g. ergs/s/cm2/Angstrom( or Hz) how can I calculate the flux, i.e. ergs/s/cm2?

I have light spectral data from astronomy data bases in flux density (flux/Angstrom or flux/Hz) and would like to calculate the flux. How can I calculate the flux from the flux density?
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12 views

How to calculate rest-frame luminosity in a specific wavelength band?

For instance, I have a set of templates whose y is in Jy and x is in Angstroms. I have both of their rest-frame and obs-frame wavelength (i.e. redshift). I want to know their luminosity in one ...
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1answer
50 views

How is the difference of bolometric magnitudes not dependent on the stars' radii?

The difference of 2 bolometric magnitudes is given by: $$M_{bol, ★} - M_{bol, ☉} = -2.5 \cdot \log \left( \frac{L_★}{L_☉} \right)$$ But Pogson's equation is: $$M_{bol, ★} - M_{bol, ☉} = -2.5 \cdot \...
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1answer
45 views

How do you carry errors for brightness magnitudes [duplicate]

I have a value for the relative flux $F_2/F_1$. With some uncertainty value $a$. If I use the equation to get relative magnitude: $m_1 - m_2 = 2.5 \log_{10}(F_2/F_1)$ How do you now calculate the ...
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0answers
24 views

How to calculate the flux of a galaxy merger? [closed]

Say three galaxies, with equal fluxes, $f_1$, merge. How could I calculate their combined flux?
3
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1answer
52 views

How much does the equivalent width of a line change by the introduction of 5% scattered light?

How much does the equivalent width of a line change by the introduction of 5% scattered light? We know the equivalent width is defined as $W = \int_{-\infty}^{\infty} \bigg(\frac{1-F_{\nu}}{F_c}\bigg) ...
2
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1answer
48 views

Using SDSS data / finding a catalog

I am looking for a catalog of low redshift galaxies (preferably SDSS) with information on line fluxes and stellar mass. My Google searches keep pointing me to work by the Portsmouth group, so I ...
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1answer
62 views

Determining needed exposure time given SNR

I need help on how to estimate an exposure time for a desirable signal to noise ratio (SNR). For example, given the magnitude and a desired SNR of a star we want to achieve, how long should the ...
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0answers
32 views

What is the O[III]/H$\alpha$ line ratio for Active Galactic Nuclei?

I have the H$\alpha$ line flux of an AGN and I am trying to calculate the Bolometric luminosity using it. Bolometric luminosity can be calculated from O[III] fluxes by $L_{\rm Bol} = 3500 L_{\rm O[III]...
4
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1answer
82 views

Flux density from brightness map

This is a naive question. I have a temperature map of radio emission at 1420 MHz, in Kelvin. I want to extract the flux density (in Janskys) from an extended region of this map. Is the flux density ($...
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0answers
52 views

Conversion of Magnitude to flux using zero point in AB Magnitude

I want to calculate the flux of the 5 sigma limited magnitude. It is given that the zero point magnitude of NB964 is 28.77 and 5sigma magnitude is 25.45. The following example is from A large, deep ...
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0answers
115 views

Units confusion while calculating flux of a star using distance and luminosity, Python

I am trying to calculate the flux of various stars in Python. I am using the information from a database containing all stars in Hipparcos, Yale Bright Star, and Gliese catalogs (almost 120,000 stars)....
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50 views

How to calculate the light energy of a supernova? [closed]

I have been given a distance, an average flux, and a time period. How do I find the light energy emitted of a supernova over that time period?