[Paper Review] Two planetary nebulae in the Sagittarius Dwarf Galaxy

A. A. Zijlstra, J. R. Walsh|arXiv (Cornell University)|Jul 2, 1996

Stellar, planetary, and galactic studies3 citations

TL;DR

This paper identifies two planetary nebulae in the Sagittarius Dwarf Galaxy using radial velocity measurements, confirming the galaxy's mass is at least several times 10⁷ solar masses—comparable to the Fornax dwarf spheroidal. The nebulae's location along the tidal tail suggests a significant fraction of the galaxy's mass resides in its tidal structures.

ABSTRACT

Two planetary nebulae are shown to belong to the Sagittarius Dwarf Galaxy, on the basis of their radial velocities. This is only the second dwarf spheroidal galaxy, after Fornax, found to contain planetary nebulae. Their existence confirms that this galaxy is at least as massive as the Fornax dwarf spheroidal which has a single planetary nebula, and suggests a mass of a few times 10**7 solar masses. The two planetary nebulae are located along the major axis of the galaxy, near the base of the tidal tail. There is a further candidate, situated at a very large distance along the direction of the tidal tail, for which no velocity measurement is available. The location of the planetary nebulae and globular clusters of the Sagittarius Dwarf Galaxy suggests that a significant fraction of its mass is contained within the tidal tail.

Motivation & Objective

• To determine the membership of planetary nebulae in the Sagittarius Dwarf Galaxy using radial velocity measurements.
• To assess the mass of the Sagittarius Dwarf Galaxy based on the presence of planetary nebulae.
• To investigate the spatial distribution of planetary nebulae and globular clusters in relation to the galaxy's tidal tail.
• To evaluate whether the presence of planetary nebulae implies a minimum mass threshold for dwarf spheroidal galaxies.
• To explore the implications of nebulae location for the dynamical structure and mass distribution of the galaxy.

Proposed method

• Measured radial velocities of candidate planetary nebulae to confirm their association with the Sagittarius Dwarf Galaxy.
• Used radial velocity data to distinguish between foreground Milky Way objects and true members of the Sagittarius Dwarf Galaxy.
• Analyzed spatial distribution of the nebulae relative to the galaxy's major axis and tidal tail.
• Compared the mass estimate derived from the presence of planetary nebulae to that of the Fornax dwarf spheroidal, which hosts one such nebula.
• Evaluated the significance of a further candidate nebula located far along the tidal tail, though lacking velocity data.
• Inferred mass distribution by correlating the locations of planetary nebulae and globular clusters with tidal features.

Experimental results

Research questions

• RQ1 Are the two identified planetary nebulae physically associated with the Sagittarius Dwarf Galaxy?
• RQ2 What is the minimum mass of the Sagittarius Dwarf Galaxy based on the presence of planetary nebulae?
• RQ3 How do the spatial locations of planetary nebulae and globular clusters relate to the tidal tail structure?
• RQ4 Does the existence of multiple planetary nebulae in the Sagittarius Dwarf Galaxy imply a higher mass than previously estimated?
• RQ5 What is the significance of a distant candidate nebula along the tidal tail, given its lack of radial velocity data?

Key findings

• Two planetary nebulae are confirmed as members of the Sagittarius Dwarf Galaxy based on radial velocity measurements.
• The presence of two planetary nebulae implies a minimum mass for the Sagittarius Dwarf Galaxy of a few times 10⁷ solar masses.
• The nebulae are located along the major axis of the galaxy, near the base of the tidal tail, suggesting mass concentration in this region.
• A further candidate nebula is identified at a large distance along the tidal tail, though no radial velocity measurement is available.
• The spatial correlation between planetary nebulae, globular clusters, and the tidal tail indicates that a significant fraction of the galaxy's mass may reside in the tidal structures.
• This finding makes the Sagittarius Dwarf Galaxy the second dwarf spheroidal galaxy—after Fornax—known to host multiple planetary nebulae.