Breaking the law: A revised view of the relation between the sizes and masses of galaxies since z 3
Abstract
The most massive galaxies at z~2 live today in the centers of groups- and cluster-sized halos and host the most extreme black holes, such as that seen in M87. Because they are rare, little is known about the structure of these galaxies during their build-up at early epochs. With the advent of the Drift And SHift (DASH) technique with the Hubble Space Telescope, we have tripled the extragalactic survey area in the near-infrared at HST resolution, allowing us to conduct a structural study of a large sample of these massive galaxies. I will present the first results from the COSMOS-DASH survey, the widest HST imaging survey that has so far been done in near-IR. We find that the sizes of the most massive galaxies are larger than expected from an extrapolation of the low mass size - M∗ relation. Hence, we reassess the size - M∗ relation with a broken power law, with a clear change of slope at a pivot mass. We find remarkable agreement between the pivot stellar masses and slopes of Mhalo - M∗ and size - M∗relations suggesting that the pivot mass reflects a transition from dissipational to dissipationless galaxy growth in both the cases. Furthermore, using ALMA observations of molecular gas kinematics of massive galaxies we find that there maybe an inclination bias in the size - M∗ relation due to dust and projection effect. Taken together, our results suggest a straightforward relation between the size scale of dark matter halos and that of galaxies, with the effects of dust and young stars being the main remaining uncertainty. This issue will be resolved with early JWST observations, providing rest-frame 3 micron morphologies of galaxies.
- Publication:
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American Astronomical Society Meeting Abstracts #235
- Pub Date:
- January 2020
- Bibcode:
- 2020AAS...23522802M