Metallicity Measurements of Gamma-Ray Burst and Supernova Explosion Sites: Lessons from HII regions in M31

Abstract

We examine how the small-scale ($<$\,kpc) variation of metallicity within a galaxy, which is found in nearby galaxies, affect the observational estimates of metallicity in the explosion sites of transient events such as core-collapse supernovae (CC SNe) and gamma-ray bursts (GRBs). Assuming the same luminosity, metallicity, and spatial distributions of \ion{H}{ii}\ regions (hereafter HIIRs) as observed in M31, we compute the apparent metallicities that we would obtain when the spectrum of a target region is blended with those of surrounding HIIRs within the length scale of typical spatial resolution. When the spatial resolution of spectroscopy is $\lesssim$ 0.5\,kpc, which is typical for the existing studies of CC SN sites, we find that the apparent metallicities reflect the metallicities of target regions, but with significant systematic uncertainties in some cases. When the spatial resolution is $\gtrsim$ 1.0 kpc, regardless of the target regions (which has a wide range of metallicity that spans $\sim$ 0.6 dex for the M31 HIIRs), we always obtain the apparent metallicities similar to the average metallicity of the M31 HIIRs. Given that the apparent metallicities measured with $\gtrsim$\,kpc scale resolution do not necessarily reflect the immediate environment of the stellar explosions, the current observational estimates of high metallicities for some of the long GRB host galaxies do {\em not} rule out the hypothesis that the long GRBs are exclusively born in a low-metallicity environment.

13 pages, 11 figures, 2 tables, added discussion about other metallicity indicators than N2 index, accepted for publication in MNRAS

References in corpus (17)

• Long gamma-ray bursts and core-collapse supernovae have different environments
• A Survey of Local Group Galaxies Currently Forming Stars. I. UBVRI Photometry of Stars in M31 and M33
• The Galaxy Population Hosting Gamma-Ray Bursts
• Measured Metallicities at the Sites of Nearby Broad-Lined Type Ic Supernovae and Implications for the SN-GRB Connection
• Long Gamma-Ray Bursts and Type Ic Core Collapse Supernovae Have Similar Locations in Hosts
• A Survey of Local Group Galaxies Currently Forming Stars: III. A Search for Luminous Blue Variables and Other H-alpha Emission-Lined Stars
• The M33 Metallicity Project: Resolving the Abundance Gradient Discrepancies in M33
• Reconciling the Metallicity Distributions of Gamma-ray Burst, Damped Lyman-alpha, and Lyman-break Galaxies at z=3
• Progenitor Diagnostics for Stripped Core-Collapse Supernovae: Measured Metallicities at Explosion Sites
• Spatially resolved properties of the GRB 060505 host: implications for the nature of the progenitor
• IFU observations of the GRB 980425/SN 1998bw host galaxy: emission line ratios in GRB regions
• Chemical composition and mixing in giant HII regions: NGC3603, 30Doradus, and N66
• The properties of SN Ib/c locations
• The host of the SN-less GRB 060505 in high resolution
• Small scale behavior of the physical conditions and the abundance discrepancy in the Orion nebula
• Do Wolf-Rayet stars have similar locations in hosts as type Ib/c supernovae and long gamma-ray bursts?
• The SAMI Galaxy Survey: The discovery of a luminous, low-metallicity H II complex in the dwarf galaxy GAMA J141103.98-003242.3

Cited by in corpus (2)

• The chemical enrichment of long-GRB nurseries up to z=2
• The Redshift and Metallicity of the Host Galaxy of Dark GRB 080325 at z=1.78