Questions tagged [spectra]
Questions about the observed frequency range of the electromagnetic radiation of a celestial object.
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How to obtain exoplanets transmission spectra from JWST's NIRISS data of WASP96?
I was having a look at JWST's NIRISS data of WASP96 (specifically at the x1dints fits file which should be already calibrated). From this, I would like to obtain a result in a fashion similar to the ...
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How to find the resolution of a spectrum?
I have been tasked to find the resolutions of a few synthetic spectra (wavelength in A vs. flux) of different stars and degrade them to the resolution of the observed spectra. But, I am not sure how ...
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How are plage regions related to the density of medium and velocity FeII ions?
During a literature review (abstract), I found that the intensity of FeII (298.5 nm) ions in the last solar minimum was higher than the two previous solar minima 21 & 22. The velocity of FeII ions ...
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How to fit LOSVD of a galaxy with gauss hermite parametrization
I have recovered the following LOSVD from an elliptical galaxy, that I now want to fit a gauss-hermite-parametrization to and derive the kinematical parameters rotational velocity, velocity dispersion ...
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When measuring the spectrum of an object at the zenith, is it better to orient the spectroscopic slit N-S of E-W?
If you were to measure the spectrum of an object while it's exactly at the zenith, how should you orient the slit of the spectrograph to minimise atmospheric dispersion? Is North-South or East-West ...
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How to convert spectra to log-wavelength and interpolate them into linear spacing in log-wavelength
I want to write a function that cross correlates a spectrum with a quasar template
I’d like to ask you how can I convert my flux density vs wavelength spectrum to log-wavelength. It’s not clear to me ...
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S/N binning of 2D spectral galactic data
I have the 2D spectrum of the ellipical galaxy NGC 4697 taken by a long slit spectrograph. The x-direction (horizontal) corresponds to wavelength and the y-direction (vertical) corresponds to distance ...
- 359
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What happened to the reemitted photons during recombination?
To my understanding, the Cosmic Microwave Background Radiation (CMBR) is light released during the recombination epoch where the formation of neutral hydrogen atoms allowed for a sudden drop in the ...
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what is the difference between Composite Stellar Population and Galaxy Spectral Energy Distribution?
I am reading Conroy et al. (2013), an extensive review on Stellar Population Synthesis technique, and I really can't get the difference between Composite Stellar Population and Spectral Energy ...
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How to handle empty tables returned by astroquery Nist.query() in Python?
I'm writing a code to extract wavelengths of certain species of atoms/ions in a given wavelength range using the Nist.query() command of the Python package ...
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How to calculate S/N in galaxy absorption spectra?
I want to calculate the S/N of an galaxy absorption spectrum.
I therefore chose a part of the spectrum which contains very little to none absorption features and should be only made up of noise and ...
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Meaning of "blue continuum spectrum"?
The textbook Astrophysics in a Nutshell, talks about the "blue continuum spectrum" in relation to the spectrum of an AGN:
I know that a continuum spectrum is caused by the interaction of a ...
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How to find x-values of fourier-transformed correlation functions in velocity space?
I am trying to extract the kinematic parameters (rotation velocity, velocity dispersion, ...) of an elliptical galaxy by extracting the kinematical broadening function using the FCQ-Algortihm first ...
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Are there any SuperCam spectra available?
A lot of pictures from the SuperCam, the NavCam or the Mastcam onboard the Perseverance rover are available online (for instance on the NASA and JPL websites). Have any SuperCam spectra been made ...
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How to remove redshift from galaxy spectra in Python?
Hello I extracted a spectrum from the central region of the 2D spectrum of the major axis from NGC 4697 (I just took a central row in the 2D data set, see this question for more information: How to ...
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How far can a star's visual colour deviate from black body radiation?
The primary driver of a star's colour is its temperature, by way of black-body radiation.
Black body radiation restricts stellar colour to a narrow slice of the full RGB spectrum.
However, all stars ...
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How would one estimate the rotation period of a star from its spectrum?
The figure is shown; the measurements were taken on two consecutive observing nights. The Ordinate is the flux normalized to continuum and the abscissa is the wavelength scale. You can see the "...
CommunityBot
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starting from SSP spectra to evaluate galaxy spectrum and observed mag
I know that the galaxy spectrum, namely the flux per unit wavelength versus the wavelength, is the sum of the Simple Stellar Population (SSP) spectra at a fixed redshift (e.g. similar to eq. 1 in ...
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Spectra of different stellar classes?
I'm beyond an amateur, but I've been failing to find this information and it makes me think I'm missing something.
Anyway: I am trying to write a procedurally generated simulation that includes ...
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Spectral lines of the Sun?
If I remember correctly, the pp chain and (partially) the CNO cycle are the dominating set of reactions in our Sun. On the other hand, the composition of the Sun has many more elements/isotopes than ...
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How to extract galaxy spectra for different radii in Python for spectra taken by long slit spectrograph?
I am trying to extract the kinematics from the elliptical galaxy NGC 4697 using the Fourier Correlation Quotient (FCQ) algorithm described by Bender (http://adsabs.harvard.edu/full/1990A%26A...229.....
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What type of spectrum does the Wolf-Rayet star WR137 have?
Is it an Emission Spectra or an Absorption Spectra?
I think that it's an absorption spectrum, but then why is the light intensity curve focused on elements that should not be in the star in this case, ...
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Derive LOSVD from galaxy spectrum, using fourier method
I am trying to implement a programm, that derives the kinematics (specifically the kinematic parameters: mean rotation velocity, velocity, dispersion, hermite coefficients h3 and h4) from an ...
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Why doesn't the Sun produce an emission spectrum?
I have read that the reason why the Sun produces an absorption spectrum is because the temperature drops as you go away from the center, such that as the various layers of the atmosphere of the sun ...
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Question regards to Kirchhoff’s Laws (of spectroscopy)
In the book "Horizons: exploring the universe-Cengage learning (2018)", page 210, it states that:
Observational evidence can tell you how nova explosions occur. As the explosion begins, ...
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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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H alpha - double peak (Be star)
What is the double peak in this case, please? What does the third mean? Many thanks
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How to isolate H$_\alpha$ from Nitrogen doublet emission lines
I am trying to find out line intensity and FWHM of H$_\alpha$6565 emission line from a quasar spectrum obtained from SDSS DR-14Q. Visual inspection of spectrum shows H$_\alpha$ being contaminated with ...
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about H$_\alpha$ and H$_\beta$ lines in astronomical objects' spectra
Generally there may be some line ratio between the two lines.
If H$\alpha$ is strong, it is quite possible we can see H$_\beta$ too.
Is it possible we can see H$_\beta$, but can not see H$_\alpha$? ...
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Why is He I 6678.151 line used for investigating variations in Be stars?
Why is He I 6678.151 line used for investigating variations in Be stars? I mean, for instance, asymmetry and radial velocity. Many thanks
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Cosmic variance - Fourier Transform - a few precisions
I have posted initially on physics exchange but none answer, so I try my chance here (I am going to delete the physics exchange one) :
I cite an original report of a colleague :
If we are interested ...
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Logarithmic rebinning and continuum removal of stellar spectra
I am trying to learn how to derive the line of sight velocity distributions from galaxy spectrum to extract kinematical parameters like rotational velocity and velocity dispersion. Therefore I need to ...
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Flux vs. Velocity representation of spectra?
I'm looking for a basic explanation of the flux vs. velocity representation of a spectrum and how it's obtained from the regular flux vs. wavelength representation. A good example of this is in Arav ...
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How to determine the temperature of a star according to the strength of the line in the spectra?
Based on the comments, I have changed some things.
Below is a graph showing the relative strength of $H_\gamma$ and Fe I lines of two stars. Which star is hotter?
This is a question from the book:An ...
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Finding galaxy spectra in SDSS Catalog by object name
I am looking to find galaxy spectra of early type elliptical galaxies in the SDSS catalog by the objects name. See: https://dr12.sdss.org/advancedSearch. I dont know how to find out the PLATEID of my ...
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Spectra: What is that Supposed to Mean?
I've found this website (click here for the link), the link leads you to a problem about the velocity Andromeda is going towards the Milky way galaxy, and you can try three approaches. I like to ...
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working with stellar spectra in fits format in python
Hey I am new to working with astronomical data in Python. I wanted to start working with stellar spectra and I am having trouble with the data. To get a first look I just wanted to plot a spectra (...
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Understanding better the factors on $C_l$ in Angular power spectrum and Relation with Matter power spectrum
I am looking for an explanation on the angular power spectrum. I found this extract that is interesting but not fully understood for me (I will cite the step that I didn't understand)
"what is ...
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Is threre a relation between relative or absolute error and standard deviation for ratio of power spectra?
I have to compute the variance on this ratio, that is to say on the observable $O$ :
$$O=\left(\frac{C_{\ell, \mathrm{gal}, \mathrm{sp}}^{\prime}}{C_{\ell, \mathrm{gal}, \mathrm{ph}}^{\prime}}\right)=\...
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Spectral analysis of AGN (velocity dispersion of galaxy absorption, doppler shifts)
I was wondering what parameters I need to know/measure to calculate the velocity dispersion of a galaxy, specifically an AGN.
Also, I have spectra where there are blueshifted and redshifted ...
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Why are the wings of many strong lines, including hydrogen lines and most metal lines, stronger in Dwarfs than in Supergiants?
What is the reason? Is it because Dwarfs have higher surface gravity (log g), in turn related to pressure, than Supergiants so there is more contribution from van der Waals and Stark broadening?
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.mt file convert to .fits/.ascii/.dat
How to convert .mt file with a spectrum to a more convenient format, please? I am able to display that in fv: Fits Viewer, but I am lost in converting. Thank you
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What leads an observer to choose a narrow slit over a wide one (and vice-versa) when observing?
In spectroscopy, a wide slit will lead to lower spectral resolution while too narrow of a slit will reduce incoming flux from the object. From what I read, it appears as though there is always a ...
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Clarification of radio spectrum terminology
For a radio spectrum, when is it called thermal emission, synchrotron emission, self-absorbed synchrotron emission and inverted spectrum? They are all power-law and their difference is power-law index?...
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Spectrum of stars
If some specific metal is shown in a star's spectrum, does it indicate that the star has that specific metal? For example, the Sun, a G2 star, shows medium strength of Ionised Calcium in its spectrum, ...
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Spectrograph Arrangement, Noise, and Fourier Domain [closed]
If the transform of a line profile extends out to the Nyquist frequency such that we cannot see the noise level, what could we change in our spectrograph arrangement that would allow us to see the ...
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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) ...
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Formation of elements in the Sun other than helium
I just learned that the Fraunhofer lines of the Sun's spectrum indicate that the Sun contains various elements other than just hydrogen and helium (for example, Na and Fe) but don't the Sun's p-p ...
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What is the best database for identification of spectral lines?
What is the best database for the identification of spectral lines? For instance, I have a red spectrum of A0 star and I would like to recognize the most prominent lines, where to find them? Many ...
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When examining an exoplanet's atmosphere is the star's emission spectra or planet's light used?
My understanding of the main method we use to figure out an exoplanet atmosphere composition is that when a exoplanet transits their sun, visible light passes through the planet's atmosphere, and ...
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