Online Colloquium
Friday, 22 April 2022, at 01.00 p.m (UT+7)


Preliminary Test of Double Component Redshift Measurements in the SDSS Spectra

Speaker:
Sulistiyowati, M. Si., Influx Inc. & SkyLabs Org

We invite all colloquium enthusiasts to join via the Zoom link:

https://bit.ly/KolAstro220422
Meeting ID: 918 0652 5476
Passcode: AstroITB

Thank you for your attention and active participation.


Abstract

We report the results of the preliminary test detecting the possibility of a secondary component in the SDSS spectra in addition to the primary object whose redshift was measured by SDSS. The primary component redshift in question is the value obtained by the SDSS spectrum by assuming a single object model in the fitting process. In our system, Double-Gaussian fitting is initially performed on the residual spectra to search for redshift candidates for secondary components. Next, fitting using the full galaxy template is performed to match the complete set of lines to the residual spectrum to obtain the best redshift for the secondary component. The SDSS spectrum is matched against two types of templates: red galaxies and blue galaxies. We then build a scoring system to determine the classification of the detected secondary objects and their redshift values. Of the 18 targets that matched the secondary component are red galaxies, 15 have redshifts that matched the previous study. The remaining three have redshifts that are too high to measure on the SDSS spectrum range. Meanwhile, of the 6 targets that matched the secondary component are blue galaxies, none has redshift that matched the previous study. These results indicate that for time being, our system is more sensitive in measuring the redshift of red galaxies — correlated with absorption lines, compared to blue galaxies — correlated with emission lines. Further testing and discussion are still needed so that the system is able to accurately measure the redshift of all types of secondary objects.


Poster