A new look at local ultraluminous infrared galaxies: the atlas and radiative transfer models of their complex physics
(2022)
MeerKAT uncovers the physics of an odd radio circle
Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 513:1 (2022) 1300-1316
Stellar and black hole assembly in z<0.3 infrared-luminous mergers: intermittent starbursts vs. super-Eddington accretion
(2022)
On the viability of determining galaxy properties from observations I: Star formation rates and kinematics
Monthly Notices of the Royal Astronomical Society Oxford University Press 513:3 (2022) 3906-3924
Abstract:
We explore how observations relate to the physical properties of the emitting galaxies by post-processing a pair of merging z ∼ 2 galaxies from the cosmological, hydrodynamical simulation NEWHORIZON, using LCARS (Light from Cloudy Added to RAMSES) to encode the physical properties of the simulated galaxy into H α emission line. By carrying out mock observations and analysis on these data cubes, we ascertain which physical properties of the galaxy will be recoverable with the HARMONI spectrograph on the European Extremely Large Telescope (ELT). We are able to estimate the galaxy’s star formation rate and dynamical mass to a reasonable degree of accuracy, with values within a factor of 1.81 and 1.38 of the true value. The kinematic structure of the galaxy is also recovered in mock observations. Furthermore, we are able to recover radial profiles of the velocity dispersion and are therefore able to calculate how the dynamical ratio varies as a function of distance from the galaxy centre. Finally, we show that when calculated on galaxy scales the dynamical ratio does not always provide a reliable measure of a galaxy’s stability against gravity or act as an indicator of a minor merger.
The Sensitivity of GPz Estimates of Photo-z Posterior PDFs to Realistically Complex Training Set Imperfections
Publications of the Astronomical Society of the Pacific, Volume 134, Number 1034
Abstract:
The accurate estimation of photometric redshifts is crucial to many upcoming galaxy surveys, for example, the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). Almost all Rubin extragalactic and cosmological science requires accurate and precise calculation of photometric redshifts; many diverse approaches to this problem are currently in the process of being developed, validated, and tested. In this work, we use the photometric redshift code GPz to examine two realistically complex training set imperfections scenarios for machine learning based photometric redshift calculation: (i) where the spectroscopic training set has a very different distribution in color–magnitude space to the test set, and (ii) where the effect of emission line confusion causes a fraction of the training spectroscopic sample to not have the true redshift. By evaluating the sensitivity of GPz to a range of increasingly severe imperfections, with a range of metrics (both of photo-z point estimates as well as posterior probability distribution functions, PDFs), we quantify the degree to which predictions get worse with higher degrees of degradation. In particular, we find that there is a substantial drop-off in photo-z quality when line-confusion goes above ∼1%, and sample incompleteness below a redshift of 1.5, for an experimental setup using data from the Buzzard Flock synthetic sky catalogs.