4 research outputs found
Color Transformations of Photometric Measurements of Galaxies in Optical and Near-Infrared Wide-Field Imaging Surveys
Over the past 2 decades, wide-field photometric surveys in optical and
infrared domains reached a nearly all-sky coverage thanks to numerous
observational facilities operating in both hemispheres. However, subtle
differences among exact realizations of Johnson and SDSS photometric systems
require one to convert photometric measurements into the same system prior to
analysis of composite datasets originating from multiple surveys. It turns out
that the published photometric transformations lead to substantial biases when
applied to integrated photometry of galaxies from the corresponding catalogs.
Here we present photometric transformations based on piece-wise linear
approximations of integrated photometry of galaxies in the optical surveys
SDSS, DECaLS, BASS, MzLS, DES, DELVE, KiDS, VST ATLAS, and the near-infrared
surveys UKIDSS, UHS, VHS, and VIKING. We validate our transformations by
constructing k-corrected color-magnitude diagrams of non-active galaxies and
measuring the position and tightness of the "red sequence". We also provide
transformations for aperture magnitudes and show how they are affected by the
image quality difference among the surveys. We present the implementation of
the derived transformations in Python and IDL and also a web-based color
transformation calculator for galaxies. By comparing DECaLS and DES, we
identified systematic issues in DECaLS photometry for extended galaxies, which
we attribute to the photometric software package used by DECaLS. As an
application of our method, we compiled two multi-wavelength photometric
catalogs for over 200,000 low- and intermediate-redshift galaxies originating
from CfA FAST and Hectospec spectral archives.Comment: 24 pages, 21 figures, accepted for publication in PASP. The "Color
transformations" web service and the Python and IDL codes are available at
https://colors.voxastro.org
The volume density of giant low surface brightness galaxies
Rare giant low surface brightness galaxies (gLSBGs) act as a stress test for the modern galaxy formation paradigm. To answer the question `How rare are they?' we estimate their volume density in the local Universe. A visual inspection of 120~sq.~deg. covered by deep Subaru Hyper Suprime-Cam data was performed independently by four team members. We detected 42 giant disky systems at with either -band 27.7~mag~arcsec isophotal radius or four disc scalelengths ~kpc, 37 of which had low central surface brightness ( mag~arcsec). This corresponds to volume densities of 4.70 Mpc for all galaxies with giant extended discs and 4.04 Mpc for gLSBGs which converts to thousand such galaxies in the entire sky out to . These estimates agree well with the result of the EAGLE cosmological hydrodynamical simulation. Giant disky galaxies represent the large-size end of the volume density distribution of normal-sized spirals, suggesting the non-exceptional nature of giant discs. We observe a high active galactic nucleus fraction among the newly found gLSBGs. The result of the EAGLE simulation suggests that minor and major mergers are the dominant channels of gLSBG formation, and observed properties of newly found galaxies support this hypothesis
The volume density of giant low surface brightness galaxies
Rare giant low surface brightness galaxies (gLSBGs) act as a stress test for the modern galaxy formation paradigm. To answer the question `How rare are they?' we estimate their volume density in the local Universe. A visual inspection of 120~sq.~deg. covered by deep Subaru Hyper Suprime-Cam data was performed independently by four team members. We detected 42 giant disky systems at with either -band 27.7~mag~arcsec isophotal radius or four disc scalelengths ~kpc, 37 of which had low central surface brightness ( mag~arcsec). This corresponds to volume densities of 4.70 Mpc for all galaxies with giant extended discs and 4.04 Mpc for gLSBGs which converts to thousand such galaxies in the entire sky out to . These estimates agree well with the result of the EAGLE cosmological hydrodynamical simulation. Giant disky galaxies represent the large-size end of the volume density distribution of normal-sized spirals, suggesting the non-exceptional nature of giant discs. We observe a high active galactic nucleus fraction among the newly found gLSBGs. The result of the EAGLE simulation suggests that minor and major mergers are the dominant channels of gLSBG formation, and observed properties of newly found galaxies support this hypothesis
The volume density of giant low surface brightness galaxies
Rare giant low surface brightness galaxies (gLSBGs) act as a stress test for the modern galaxy formation paradigm. To answer the question `How rare are they?' we estimate their volume density in the local Universe. A visual inspection of 120~sq.~deg. covered by deep Subaru Hyper Suprime-Cam data was performed independently by four team members. We detected 42 giant disky systems at with either -band 27.7~mag~arcsec isophotal radius or four disc scalelengths ~kpc, 37 of which had low central surface brightness ( mag~arcsec). This corresponds to volume densities of 4.70 Mpc for all galaxies with giant extended discs and 4.04 Mpc for gLSBGs which converts to thousand such galaxies in the entire sky out to . These estimates agree well with the result of the EAGLE cosmological hydrodynamical simulation. Giant disky galaxies represent the large-size end of the volume density distribution of normal-sized spirals, suggesting the non-exceptional nature of giant discs. We observe a high active galactic nucleus fraction among the newly found gLSBGs. The result of the EAGLE simulation suggests that minor and major mergers are the dominant channels of gLSBG formation, and observed properties of newly found galaxies support this hypothesis