Modeling the Infrared Extinction toward the Galactic Center

TL;DR

This paper models the infrared extinction toward the Galactic Center using a silicate-graphite dust model, highlighting challenges in fitting the entire IR range and suggesting a multi-environment dust composition as a solution.

Contribution

It provides a detailed dust model fitting the IR extinction curve toward the GC and discusses the limitations and possible multi-environment dust contributions.

Findings

Best-fit visual extinction: Av~38--42 mag

Difficulty in fitting both near-IR and mid-IR extinction simultaneously

Proposed multi-environment dust model to explain extinction variations

Abstract

We model the ~1--19$\mum$ infrared (IR) extinction curve toward the Galactic Center (GC) in terms of the standard silicate-graphite interstellar dust model. The grains are taken to have a power law size distribution with an exponential decay above some size. The best-fit model for the GC IR extinction constrains the visual extinction to be Av~38--42 mag. The limitation of the model, i.e., its difficulty in simultaneously reproducing both the steep ~1--3$\mum$ near-IR extinction and the flat ~3--8$\mum$ mid-IR extinction is discussed. We argue that this difficulty could be alleviated by attributing the extinction toward the GC to a combination of dust in different environments: dust in diffuse regions (characterized by small Rv and steep near-IR extinction), and dust in dense regions (characterized by large Rv and flat UV extinction).