Browsing by Author "Ponomareva, Anastasia"

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    MIGHTEE-HI: discovery of an HI-rich galaxy group at z = 0.044 with MeerKAT
    (Monthly Notices of the Royal Astronomical Society, 2021) Ranchod, Shilpa; Deane, Roger; Ponomareva, Anastasia
    We present the serendipitous discovery of a galaxy group in the XMM-LSS field with MIGHTEE Early Science observations. 20 galaxies are detected in HI in this z ∼ 0.044 group, with a 3σ column density sensitivity of NHI = 1.6 × 1020 cm−2. This group has not been previously identified, despite residing in a well-studied extragalactic legacy field. We present spatially resolved HI 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 HI-to-stellar mass ratio of log10 (f∗HI) = −0.2, which is 0.7 dex greater than expected. The group’s high HI 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 HI 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.
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    MIGHTEE-HI: the radial acceleration relation with resolved stellar mass measurements
    (Oxford University Press, 2025) Jarvis, Matt; Ponomareva, Anastasia; Vărăşteanu, Andreea
    The radial acceleration relation (RAR) is a fundamental relation linking baryonic and dark matter in galaxies by relating the observed acceleration derived from dynamics to the one estimated from the baryonic mass. This relation exhibits small scatter, thus providing key constraints for models of galaxy formation and evolution – allowing us to map the distribution of dark matter in galaxies – as well as models of modified dynamics. However, it has only been extensively studied in the very local Universe with largely heterogeneous samples. We present a new measurement of the RAR, utilizing a homogeneous sample of 19 H i-selected galaxies out to $z=0.08$. We introduce a novel approach of measuring resolved stellar masses using spectral energy distribution fitting across 10 photometric bands to determine the resolved mass-to-light ratio, which we show is essential for measuring the acceleration due to baryons in the low-acceleration regime. Our results reveal a tight RAR with a low-acceleration power-law slope of $\sim 0.5$, consistent with previous studies. Adopting a spatially varying mass-to-light ratio yields the tightest RAR with an intrinsic scatter of only $0.045 \pm 0.022$ dex, highlighting the importance of resolved stellar mass measurements in accurately characterizing the gravitational contribution of the baryons in low-mass, gas-rich galaxies. We also find the first tentative evidence for redshift evolution in the acceleration scale, but more data will be required to confirm this. Adopting a more general MOND interpolating function, we find that our results ameliorate the tension between previous RAR analyses, the Solar System quadrupole, and wide-binary test.