Satellite group infall into the Milky Way: Exploring the Crater-Leo case with new HST proper motions

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Volume 687 (July 2024)

A&A, 687 (2024) A212

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Table 4.

Derived orbital parameters of Crater-Leo objects: the pericentre (r_peri), apocentre (r_apo), and eccentricity (e).

MW-only	r_peri (kpc)			r_apo (kpc)			e			t_peri (Gyr)			Bound orbits (%)

Object	Gaia	HST	Predicted	Gaia	HST	Predicted	Gaia	HST	Predicted	Gaia	HST	Predicted	Gaia	HST
Leo II	$71_{- 18}^{+ 26}$ $71^{+26}_{-18}$	–	$48_{- 10}^{+ 16}$ $48^{+16}_{-10}$	$226_{- 9}^{+ 9}$ $226^{+9}_{-9}$	–	$225_{- 7}^{+ 7}$ $225^{+7}_{-7}$	$0 . 55_{- 0.10}^{+ 0.11}$ $0.55^{+0.11}_{-0.10}$	–	$0 . 66_{- 0.08}^{+ 0.07}$ $0.66^{+0.07}_{-0.08}$	$- 2 . 1_{- 0.1}^{+ 0.1}$ $-2.1^{+0.1}_{-0.1}$	–	$- 1 . 9_{- 0.1}^{+ 0.1}$ $-1.9^{+0.1}_{-0.1}$	83%	–
Leo IV	$87_{- 24}^{+ 24}$ $87^{+24}_{-24}$	$110_{- 25}^{+ 14}$ $110^{+14}_{-25}$	$56_{- 10}^{+ 16}$ $56^{+16}_{-10}$	$176_{- 10}^{+ 60}$ $176^{+60}_{-10}$	$185_{- 10}^{+ 54}$ $185^{+54}_{-10}$	$156_{- 5}^{+ 6}$ $156^{+6}_{-5}$	$0 . 39_{- 0.11}^{+ 0.16}$ $0.39^{+0.16}_{-0.11}$	$0 . 27_{- 0.06}^{+ 0.13}$ $0.27^{+0.13}_{-0.06}$	$0 . 48_{- 0.09}^{+ 0.08}$ $0.48^{+0.08}_{-0.09}$	$- 1 . 3_{- 0.4}^{+ 0.5}$ $-1.3^{+0.5}_{-0.4}$	$- 1 . 2_{- 0.2}^{+ 0.3}$ $-1.2^{+0.3}_{-0.2}$	$- 1 . 6_{- 0.1}^{+ 0.1}$ $-1.6^{+0.1}_{-0.1}$	70%	91%
Leo V	$93_{- 24}^{+ 17}$ $93^{+17}_{-24}$	$87_{- 23}^{+ 18}$ $87^{+18}_{-23}$	$40_{- 8}^{+ 13}$ $40^{+13}_{-8}$	$236_{- 16}^{+ 33}$ $236^{+33}_{-16}$	$234_{- 15}^{+ 34}$ $234^{+34}_{-15}$	$207_{- 8}^{+ 10}$ $207^{+10}_{-8}$	$0 . 47_{- 0.04}^{+ 0.13}$ $0.47^{+0.13}_{-0.04}$	$0 . 49_{- 0.05}^{+ 0.13}$ $0.49^{+0.13}_{-0.05}$	$0 . 62_{- 0.06}^{+ 0.06}$ $0.62^{+0.06}_{-0.06}$	$- 1 . 2_{- 0.1}^{+ 0.2}$ $-1.2^{+0.2}_{-0.1}$	$- 1 . 2_{- 0.1}^{+ 0.2}$ $-1.2^{+0.2}_{-0.1}$	$- 1 . 3_{- 0.1}^{+ 0.1}$ $-1.3^{+0.1}_{-0.1}$	14%	19%
Crater 1	$76_{- 20}^{+ 24}$ $76^{+24}_{-20}$	–	$59_{- 9}^{+ 15}$ $59^{+15}_{-9}$	$154_{- 7}^{+ 53}$ $154^{+53}_{-7}$	–	$145_{- 4}^{+ 5}$ $145^{+5}_{-4}$	$0 . 39_{- 0.11}^{+ 0.16}$ $0.39^{+0.16}_{-0.11}$	–	$0 . 43_{- 0.08}^{+ 0.07}$ $0.43^{+0.07}_{-0.08}$	$- 1 . 8_{- 1.3}^{+ 0.5}$ $-1.8^{+0.5}_{-1.3}$	–	$- 1 . 6_{- 0.1}^{+ 0.1}$ $-1.6^{+0.1}_{-0.1}$	70%	–

MW+LMC
Leo II	$111_{- 20}^{+ 11}$ $111^{+11}_{-20}$	–	$48_{- 10}^{+ 18}$ $48^{+18}_{-10}$	$217_{- 10}^{+ 23}$ $217^{+23}_{-10}$	–	$225_{- 7}^{+ 7}$ $225^{+7}_{-7}$	$0 . 41_{- 0.09}^{+ 0.13}$ $0.41^{+0.13}_{-0.09}$	–	$0 . 66_{- 0.08}^{+ 0.07}$ $0.66^{+0.07}_{-0.08}$	$- 1 . 8_{- 0.3}^{+ 0.1}$ $-1.8^{+0.1}_{-0.3}$	–	$- 2 . 0_{- 0.1}^{+ 0.1}$ $-2.0^{+0.1}_{-0.1}$	77%	–
Leo IV	$81_{- 18}^{+ 27}$ $81^{+27}_{-18}$	$94_{- 16}^{+ 8}$ $94^{+8}_{-16}$	$56_{- 10}^{+ 16}$ $56^{+16}_{-10}$	$163_{- 10}^{+ 56}$ $163^{+56}_{-10}$	$163_{- 10}^{+ 50}$ $163^{+50}_{-10}$	$156_{- 5}^{+ 6}$ $156^{+6}_{-5}$	$0 . 42_{- 0.16}^{+ 0.14}$ $0.42^{+0.14}_{-0.16}$	$0 . 34_{- 0.09}^{+ 0.14}$ $0.34^{+0.14}_{-0.09}$	$0 . 48_{- 0.09}^{+ 0.08}$ $0.48^{+0.08}_{-0.09}$	$- 1 . 6_{- 1.2}^{+ 0.6}$ $-1.6^{+0.6}_{-1.2}$	$- 1 . 2_{- 0.3}^{+ 0.1}$ $-1.2^{+0.1}_{-0.3}$	$- 1 . 6_{- 0.1}^{+ 0.1}$ $-1.6^{+0.1}_{-0.1}$	65%	97%
Leo V	$111_{- 30}^{+ 18}$ $111^{+18}_{-30}$	$100_{- 27}^{+ 23}$ $100^{+23}_{-27}$	$50_{- 9}^{+ 13}$ $50^{+13}_{-9}$	$198_{- 14}^{+ 54}$ $198^{+54}_{-14}$	$184_{- 12}^{+ 51}$ $184^{+51}_{-12}$	$207_{- 8}^{+ 10}$ $207^{+10}_{-8}$	$0 . 32_{- 0.09}^{+ 0.18}$ $0.32^{+0.18}_{-0.09}$	$0 . 35_{- 0.10}^{+ 0.17}$ $0.35^{+0.17}_{-0.10}$	$0 . 62_{- 0.06}^{+ 0.06}$ $0.62^{+0.06}_{-0.06}$	$- 1 . 3_{- 0.5}^{+ 0.3}$ $-1.3^{+0.3}_{-0.5}$	$- 1 . 5_{- 0.4}^{+ 0.4}$ $-1.5^{+0.4}_{-0.4}$	$- 1 . 3_{- 0.1}^{+ 0.1}$ $-1.3^{+0.1}_{-0.1}$	17%	26%
Crater 1	$52_{- 14}^{+ 27}$ $52^{+27}_{-14}$	–	$59_{- 9}^{+ 15}$ $59^{+15}_{-9}$	$154_{- 6}^{+ 26}$ $154^{+26}_{-6}$	–	$145_{- 4}^{+ 5}$ $145^{+5}_{-4}$	$0 . 54_{- 0.13}^{+ 0.12}$ $0.54^{+0.12}_{-0.13}$	–	$0 . 43_{- 0.08}^{+ 0.07}$ $0.43^{+0.07}_{-0.08}$	$- 2 . 3_{- 1.0}^{+ 0.5}$ $-2.3^{+0.5}_{-1.0}$	–	$- 1 . 6_{- 0.1}^{+ 0.1}$ $-1.6^{+0.1}_{-0.1}$	78%	–

Notes. We compare the derived orbital parameters using the proper motions described in Table 2 (Gaia DR3) with the ones derived using the predicted proper motions with the Lynden-Bell method described in Sect. 4.2 (Predicted). For Leo IV and Leo V, we also derive the orbital parameters using our new HST proper motions (HST). For all the derived orbital parameters, the properties described in Table 1 were used. We also mention the percentage of bound orbits that we get for each object. We do this for both the MW-only potential and the MW+LMC potential.

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