MIGHTEE-HI: discovery of an H I-rich galaxy group at z = 0.044 with MeerKAT
Monthly Notices of the Royal Astronomical Society Oxford University Press 506:2 (2021) 2753-2765
Abstract:
We present the serendipitous discovery of a galaxy group in the XMM-LSS field with MIGHTEE Early Science observations. 20 galaxies are detected in H I in this z ∼ 0.044 group, with a 3σ column density sensitivity of NHI=1.6×1020cm−2. This group has not been previously identified, despite residing in a well-studied extragalactic legacy field. We present spatially resolved H I total intensity and velocity maps for each of the objects which reveal environmental influence through disturbed morphologies. The group has a dynamical mass of log10(Mdyn/M⊙)=12.32, and is unusually gas-rich, with an H I-to-stellar mass ratio of log10(f∗HI)=−0.2, which is 0.7 dex greater than expected. The group’s high H I content, spatial, velocity, and identified galaxy type distributions strongly suggest that it is in the early stages of its assembly. The discovery of this galaxy group is an example of the importance of mapping spatially resolved H I in a wide range of environments, including galaxy groups. This scientific goal has been dramatically enhanced by the high sensitivity, large field-of-view, and wide instantaneous bandwidth of the MeerKAT telescope.Evolution of the galaxy stellar mass function: evidence for an increasing M* from z = 2 to the present day
Monthly Notices of the Royal Astronomical Society Oxford University Press 506:4 (2021) 4933-4951
Abstract:
Utilizing optical and near-infrared broad-band photometry covering >5 deg2 in two of the most well-studied extragalactic legacy fields (COSMOS and XMM-LSS), we measure the galaxy stellar mass function (GSMF) between 0.1 < z < 2.0. We explore in detail the effect of two source extraction methods (SExtractor and ProFound) in addition to the inclusion/exclusion of Spitzer IRAC 3.6 and 4.5 μm photometry when measuring the GSMF. We find that including IRAC data reduces the number of massive (log10(M/M⊙) > 11.25) galaxies found due to improved photometric redshift accuracy, but has little effect on the more numerous lower-mass galaxies. We fit the resultant GSMFs with double Schechter functions down to log10(M/M⊙) = 7.75 (9.75) at z = 0.1 (2.0) and find that the choice of source extraction software has no significant effect on the derived best-fitting parameters. However, the choice of methodology used to correct for the Eddington bias has a larger impact on the high-mass end of the GSMF, which can partly explain the spread in derived M* values from previous studies. Using an empirical correction to model the intrinsic GSMF, we find evidence for an evolving characteristic stellar mass with δlog10(M*/M⊙)/δz = −0.16±0.05(−0.11±0.05), when using SExtractor (ProFound). We argue that with widely quenched star formation rates in massive galaxies at low redshift (z < 0.5), additional growth via mergers is required in order to sustain such an evolution to a higher characteristic mass.A fast semidiscrete optimal transport algorithm for a unique reconstruction of the early Universe
Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 506:1 (2021) 1165-1185
Microwave spectro-polarimetry of matter and radiation across space and time
Experimental Astronomy Springer Nature 51:3 (2021) 1471-1514
Abstract:
This paper discusses the science case for a sensitive spectro-polarimetric survey of the microwave sky. Such a survey would provide a tomographic and dynamic census of the three-dimensional distribution of hot gas, velocity flows, early metals, dust, and mass distribution in the entire Hubble volume, exploit CMB temperature and polarisation anisotropies down to fundamental limits, and track energy injection and absorption into the radiation background across cosmic times by measuring spectral distortions of the CMB blackbody emission. In addition to its exceptional capability for cosmology and fundamental physics, such a survey would provide an unprecedented view of microwave emissions at sub-arcminute to few-arcminute angular resolution in hundreds of frequency channels, a data set that would be of immense legacy value for many branches of astrophysics. We propose that this survey be carried out with a large space mission featuring a broad-band polarised imager and a moderate resolution spectro-imager at the focus of a 3.5 m aperture telescope actively cooled to about 8K, complemented with absolutely-calibrated Fourier Transform Spectrometer modules observing at degree-scale angular resolution in the 10–2000 GHz frequency range. We propose two observing modes: a survey mode to map the entire sky as well as a few selected wide fields, and an observatory mode for deeper observations of regions of specific interest.
Model-independent constraints on clustering and growth of cosmic structures from BOSS DR12 galaxies in harmonic space
ArXiv preprint. 14 pages, 8 figures, 3 tables
Abstract:
We present a new, model-independent measurement of the clustering amplitude of galaxies and the growth of cosmic large-scale structures from the Baryon Oscillation Spectroscopic Survey (BOSS) 12th data release (DR12). This is achieved by generalising harmonic-space power spectra for galaxy clustering to measure separately the magnitudes of the density and of the redshift-space distortion terms, which are respectively related to the clustering amplitude, bσ8(z), and the growth, fσ8(z). We adopt a tomographic approach with 15 redshift bins in the range z∈[0.15,0.67]. We restrict our analysis to strictly linear scales, implementing a redshift-dependent maximum multipole for each of the tomographic bins. Thus, we obtain 30 data points in total, 15 for each of the quantities bσ8(z) and fσ8(z). The measurements do not appear to suffer from any apparent systematic effect and show excellent agreement with the theoretical prediction from a concordance cosmology as from the Planck satellite. Our results also agree with previous analyses by the BOSS collaboration. Although each single datum has, in general, a larger error bar than that obtained in configuration- or Fourier-space analyses, our study provides the community with a larger number of tomographic data points that allow for a complementary tracking in redshift of the evolution of fundamental cosmological quantities.