Questions tagged [data-analysis]

Analysis of data is a process of inspecting, cleaning, transforming, and modeling data with the goal of discovering useful information, suggesting conclusions, and supporting decision making.

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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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1 vote
1 answer
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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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Where can I find galaxy rotational data?

I want to do a small project of generating rotational curves for different galaxies, and need data for some prominent stars in other galaxies (data needed: distance from center, rotational velocity) ...
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1 vote
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uvotdetect sometimes doesn't make valid .fits files for DS9 to read (Swift UVOT, Heasoft)

I have downloaded galactic center sky images from the Swift database (https://www.swift.ac.uk/swift_live/index.php#doSimpleSearch.php?catname=swiftmastr&searchpos=galactic+center&searchrad=10&...
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1 answer
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How do you tell if a variable star is periodic or not by its light curve?

I have light curves for a particular star. I'm able to construct a periodogram of the stars' light curve, a plot of the power of the light curve vs. the signal's period. For a nonperiodic but ...
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1 vote
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How to convert between surface density in JY/beam*KM/S / arcsec2 to mass surface density in Solar masses / pc2

I am interested in studying the gas kinematics of atomic hydrogen (21cm line) for a galaxy and have output I'd like to convert after assuming a model for my data using BBarolo. ...
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3 votes
2 answers
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Are chirped gravitational wave events generally first identified by searching through libraries of chirps?

Comments below What does "GPU-accelerated butterfly matched filtering over dense bank of time-symmetric chirp-like templates" mean? (GW170817) suggest that for this technique a library of ...
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Do I need ENVI if I want to just learn IDL?

I am trying to gain experience in IDL in order to do basic image data reduction techniques like stacking and aperture photometry, so I decided to purchase an IDL license, however, the license is ...
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2 votes
2 answers
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How to get phase-folded data (-0.5,0.5)?

How to get phase-folded data (-0.5,0.5)? For phase-folded value to the interval (0,1), I use: $$ \phi = \frac{H_{JD}-T_0}{P} \mod 1$$ $\phi$ is phase HJD is time T0 is the reference time P is the ...
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Which galaxies have the most well known / estimated dark matter halos?

For this I guess you need accurate circular velocity measurements of the stars in the galaxy a decent luminosity profile for the galaxy some analysis which looks at the discrepancy between the two ...
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1 vote
1 answer
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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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What are the applications of cross matching astronomical catalogues?

Why do we cross match astronomical catalogues at different wavelengths? What information can we determine from combining the information from two catalogues? One of the applications I read was ...
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Data of Coronal Holes

I'm working on the Evolution of coronal holes for which I need data of Coronal Holes, I have searched on internet and also done literature survey but didn't find out any open-source catalogue where I ...
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2 votes
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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 ...
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How did astronomers "measure a large (>40 degrees) misalignment between the black hole spin and the orbital spin" of MAXI J1820+70?

Gizmodo's Funky Black Hole Is Spinning Tilted says: A team of astronomers recently observed an askew black hole just 10,000 light-years from Earth. The black hole’s spin axis is out of alignment with ...
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Any package to construct a good segmentation map?

Does anyone know of any package to construct a detailed segmentation map for a given image? So far, I used the SExtractor code. However, I am simulating very faint sources and, sometimes, they are ...
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2 votes
1 answer
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What does "RV model including a GP with a quasi-periodic covariance structure" mean?

A candidate short-period sub-Earth orbiting Proxima Centauri says: 4.1 Simple periodogram analysis ]We first consider a very simple pre-whitening procedure applied to the CCF RVs in order to ...
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5 votes
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Is it possible to narrow down possible dates for the following eclipse pattern?

I am searching for an year which satisfies the following criteria. Dates are in Gregorian calendar. Criteria Year range 3800 BC to 500 BC Solar Eclipse of any kind between October 14 and October 22 ...
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2 votes
0 answers
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Is there a tool to convert N-body RAMSES simulation file formats to GADGET 2 format in Python?

I am looking for a way to convert RAMSES files to GADGET-2 binary files because I want to use the package SimSpin (https://github.com/kateharborne/SimSpin/blob/master/R/make_simspin_file.R) which is ...
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1 vote
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how to plot Gauss-Hermite moment maps from arrays of star velocity values in Python?

I want to calculate Gauss-Hermite moments, such as h1,h2, h3, h4 moments from the values in an array of numbers which represent velocity distribution of stars in a galaxy. How would I fit a curve to ...
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4 votes
2 answers
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How to interpret this spectrum of the "new DESI Quasar at z = 6.53"; what causes the big edge at about 9150 Angstroms?

I'm not exacty sure why but Scitech Daily's Seeing Dark Energy’s True Colors: DESI Creates Largest 3D Map of the Cosmos includes the graphic and caption below. It indicates a quasar in a Hubble image ...
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4 votes
1 answer
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Examples of the oldest "precoveries"; objects that were first discovered in recent data but then looking back are confirmed in much older data

Example from Ars Technica's Radio astronomers scouring the archives spotted black hole devouring a star: Astronomers found another TDE in 2020 (dubbed AT 2019qiz), which provided the first direct ...
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1 vote
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Maximum number of pixels across a synthesized beam in an ALMA image?

I have some ALMA data, from which I have created images using the TCLEAN task in CASA. I understand that with this type of data, it is necessary to have at least 2 pixels across the FWHM of the ...
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1 vote
2 answers
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Downloadable GCNS (Gaia Catalog of Nearby Stars)

Has Gaia made the "Gaia Catalog of Nearby Stars" (GCNS) available for offline processing? Ideally I'd like the full 100pc data set in a format that doesn't require any specialized libraries ...
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11 votes
2 answers
466 views

How do you propagate asymmetric errors? (on the practical way to...)

I've used uncertainties's ufloatpackage to propagate uncertainties as I thought it's the standard way to do it. Now I want to ...
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  • 525
1 vote
0 answers
120 views

How to quickly loop through many small fits files for data analysis?

I need to extract information from a few columns in ~20k different fits files with python. Each file is relatively small, ~0.2MB. I have been doing this so far with a loop and ...
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10 votes
1 answer
1k views

What is sin i in this graph and why is it there?

This is some data presented in a lecture on exoplanets that depicts the distribution of the sizes of super-Earths in comparison to the mass of Jupiter. I would like to know what the argument of the ...
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3 votes
1 answer
89 views

How to plot 68% contours?

I am doing a grid search of omega_Matter vs Omega_dark_energy by iterating over ranges of both and determining the chi-squared to determine the optimal value of both for a LambdaCDM model. I have my ...
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1 vote
1 answer
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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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4 votes
1 answer
126 views

Procedures to test an hypothesis

In the context of planet formation and with the intention of testing different migration and in situ formation scenarios, I'm wondering what are the standard procedures to test and rank different ...
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6 votes
1 answer
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Why Nyquist Sampling Rate depends on Bandwidth and not max frequency?

Is the Nyquist sampling rate same for different bands if those bands have same bandwith? E.g. Would the Nyquist Sampling rate be same for 1000-1400 MHz band as for 100-500 MHz band because both the ...
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4 votes
0 answers
52 views

How does the Hubble Space Telescope measure the speed of the wind inside Jupiter's Great Red Spot?

Space.com's Jupiter's winds of change show increased storm speeds in Great Red Spot and Hubblesite.org's Hubble Shows Winds in Jupiter's Great Red Spot are Speeding Up both link to the recent open ...
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2 votes
0 answers
19 views

What are mag_a, mag_i, mag_z, a*, and sin_i * from the SDSS Moving Objects Data?

I'm currently working on the SDSS Moving Objects data sets and came across the column names mag_a, mag_i, mag_z, aprime, and sin_iprime. Can someone describe what these attributes mean, or where I can ...
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1 vote
0 answers
27 views

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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4 votes
0 answers
66 views

Obtaining the derived period of $\omega$ Canis Majoris

I have read these two papers: On the nature of the Be phenomenon I. The case of ω Canis Majoris Stellar and circumstellar activity of the Be star ω CMa II. Periodic line-profile variability In the ...
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  • 141
1 vote
0 answers
23 views

Curated dataset of labelled images for NEO detection

I am looking for a dataset of images. Some images should contain NEO's (1 or more), others should not. With the dataset, there should also be an accompanying file, of which should contain 'labels'. ...
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  • 161
2 votes
1 answer
66 views

Extracting specific star data from Gaia DR2?

I would like to extract all Gaia DR2 sources which have six-parameter solutions as well as their radial velocities and effective temperatures. Is this possible as DR2 only specifies that there are 1,...
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2 votes
1 answer
47 views

How to calculate an infrared SED from the specific intensities?

I have values of total infrared fluxes (SED) in literature expressed in Jy (Jansky) for galaxies. I want to assure that my infrared radial profiles of the same galaxies in MJy/sr (and other in Jy/...
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1 vote
1 answer
101 views

Why histogram does not look like the Gaussian curve?

I have data consisting of radial velocities and times (covering about 10 000 days). The radial velocity changes with a period. I tried to find out the period using Stellingwerf's method (it was ...
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  • 141
3 votes
1 answer
238 views

What is z in this program?

Does z stad for the mass fraction of all the remaining chemical elements except helium and hydrogen, please? Source: https://github.com/chrysante87/pyterpol/wiki
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3 votes
0 answers
33 views

Solving the inverse problem - inspection

After solving the inverse problem*, how to investigate whether the solution is unique or not? When I check theoretical values and published values during the convergence and search for the lowest ...
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  • 141
0 votes
0 answers
25 views

What is Euclidean fluence scaling in the context of bounding constraints on FRB all-sky rates? Would non-Euclidean scaling give a different answer?

The recent Chromatic periodic activity down to 120 MHz in a Fast Radio Burst contains two paragraphs in which X's are given "assuming an Euclidean fluence scaling". To me, a non-astronomer, ...
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1 vote
0 answers
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Star Catalog with radius, luminosity, and spectra class?

I am looking for a star catalog (hopefully a .csv file) that contains radius, luminosity, and spectra class data for 1000+ stars. I have checked catalogs like the HIP, HD, and GAIA catalogs. I have ...
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1 vote
1 answer
47 views

Where do Astronomers usually get their wavelengths? Where do they turn to look up standard, accepted values for spectral features?

When identifying isolated observed spectral features or fitting complex observed spectra or even running complex numerical simulations, one needs a reliable, standard table of known wavelengths and ...
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1 vote
0 answers
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How to find published data with the article?

How to find data published with an article, please? For instance, let us consider this paper. There are data products and the link to SIMBAD on the right. Then, the table with objects appears, but ...
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7 votes
1 answer
1k views

On what basis is the information about the distance and velocity of the Voyager probes determined?

Voyager 1 was the first-ever object to reach interstellar space on August 25, 2012 when it passed beyond the sun’s realm of plasma influence (the heliosphere)[...] (source) Although some of their ...
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2 votes
2 answers
89 views

How the data collected during 5 year DESI operation will be analyzed with regards to finding what dark energy really is?

Dark Energy Spectroscopic Instrument, or DESI at the end of it's 5 years operation will create the largest 3-D spectroscopic map of the universe. How the data collected during 5 year DESI operation ...
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  • 571
6 votes
1 answer
537 views

Conventional units for astronomical object coordinates

I would like to know what the conventional units for identifying a celestial object (J2000.0) are. For instance, I am reading a paper in which they refer to object SDSSJ170013.70+400855.6; I am ...
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3 votes
0 answers
40 views

Estimate the shape of an object based on flux curve

Is there an aproximation to know the shape of a dust cloud,etc based on the magnitude/flux curves of stars they transit? Example, can I know if the shape is (at least in 2 dimensions) elliptical, ...
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4 votes
1 answer
146 views

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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