Monday, December 4, 2023

Search for Gaseous Satellites in Local Spiral Galaxies

The universe is a vast and mysterious place, filled with countless galaxies, stars and planets. As astronomers continue to study the cosmos, they are discovering new insights into the workings of the universe and the objects within it. One area of particular interest is the search for satellite galaxies around spiral galaxies in the local universe. In a recent study, astronomers Jingyao Zhu and Mary E Putman used 21 cm neutral hydrogen data from the Arecibo Legacy Fast ALFA Survey to search for gas-containing dwarf galaxies as satellite systems around nearby spiral galaxies.

The study focused on identifying 15 spiral “primary” galaxies in a local volume of 10 Mpc with a range of total masses. Within these primary galaxies’ virial volumes (R200), the researchers found 19 gas-containing dwarf satellite candidates and 46 candidates within 2R200. Their sensitivity using ALFALFA data converts to MHI ≈ 7.4 × 106 M at 10 Mpc, which includes 13 of the 26 gaseous dwarf galaxies in the Local Group. The researchers found 0-3 gaseous satellites per host galaxy within R200 and 0−5 within 2R200, which is consistent with the low numbers present for the Milky Way and M31.

The study’s findings indicate that galaxy stellar mass and environment are major factors in determining a galaxy’s star formation stage. The researchers found that local universe spiral galaxies of Milky Way mass and lower tend to have very few gaseous satellites. This finding confirms what was previously known about this area. None of the ALFALFA satellite candidates reach the high HI masses of the Milky Way’s Magellanic Clouds. Of the five most massive candidates with MHI 108 M. M, only one falls within the host’s virial radius.


The researchers compared their results with two recent deep optical surveys: ELVES in the Local Volume and SAGA at a slightly higher redshift, and with the Auriga cosmological zoom simulations of Milky Way-analogs. Within the projected virial radii of the hosts, the gaseous satellite numbers, 0-4, agreed across the different studies.

One of the most intriguing findings of the study was the role of ram pressure stripping (RPS) in quenching satellite galaxies. RPS accounts for over 50% of the quenched satellites in the Auriga cosmological simulations of Milky Way analogs. This suggests that a universal and effective satellite quenching mechanism, such as RPS by the host halo, is likely at play.

The study provides important insights into the formation and evolution of satellite galaxies around spiral galaxies in the local universe. By identifying the factors that determine a galaxy’s star formation stage and the role of environmental quenching in satellite galaxies’ evolution, astronomers can continue to deepen our understanding of the universe and the objects within it. As our knowledge of the cosmos continues to grow, it is certain that there will be many more exciting discoveries to come.







Source: Zhu, J., & Putman, M.E. (2023). Census of Gaseous Satellites around Local 
Spiral Galaxies.

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