A multiwavelength view of the ISM in the merger remnant galaxy Fornax A

Abstract

We present multi-wavelength imagery of the merger remnant galaxy NGC 1316 with an objective to study the dust content and its association with the other phases of the interstellar medium. Color-index maps as well as extinction maps derived for this galaxy reveal an intricate and complex dust morphology in NGC 1316, i.e. there is a prominent lane in the inner part, while at about 6–7 kpc it apparently takes the form of an arc-like pattern extending along the northeast direction. In addition to this, several other dust clumps and knots are also evident in this galaxy. The dust emission mapped using Spitzer data at 8 μm indicates even more complex morphological structures of the dust in NGC 1316. The extinction curve derived over the optical to near-IR bands closely follows the standard Galactic curve, suggesting similar properties of the dust grains. The dust content of NGC 1316, estimated from optical extinction, is ∼2.13 × 105 M⊙. This is a lower limit compared to that estimated using the IRAS flux densities of ∼5.17 × 106 M⊙ and the flux densities at 24, 70 and 160 μm from MIPS ∼3.2 × 107 M⊙. High resolution Chandra observations of this merger remnant system have provided an unprecedented view of the complex nature exhibited by the distribution of hot gas in NGC 1316, which closely matches the morphology of ionized gas and to some extent also the dust. X-ray color—color plots for the resolved sources within the optical D25 extent of NGC 1316 have enabled us to separate them into different classes.