Spitzer Space TelescopeObservations of Kepler’s Supernova Remnant: A Detailed Look at the Circumstellar Dust Component

Abstract

We present 3.6Y160 m infrared images of Kepler's supernova remnant (SN 1604) obtained with the IRAC and MIPS instruments on the Spitzer Space Telescope. We also present MIPS SED low-resolution spectra in the 55Y 95 m region. The observed emission in the MIPS 24 m band shows the entire shell. Emission in the MIPS 70 m and IRAC 8 m bands is seen only from the brightest regions of 24 m emission, which also correspond to the regions seen in optical H images. Shorter wavelength IRAC images are increasingly dominated by stars, although faint filaments are discernible. The SED spectrum of shows a faint continuum dropping off to longer wavelengths and confirms that strong line emission does not dominate the mid-IR spectral region. The emission we see is due primarily to warm dust emission from dust heated by the primary blast wave; no excess infrared emission is observed in regions where supernova ejecta are seen in X-rays. We use models of the dust to interpret the observed 70/24 m ratio and constrain the allowed range of temperatures and densities. We estimate the current mass of dust in the warm dust component to be 5:4 ; 10 À4 M , and infer an original mass of about 3 ; 10 À3 M before grain sputtering. The MIPS 160 m band shows no emission belonging to the remnant. We place a conservative but temperature-dependent upper limit on any cold dust component roughly a factor of 10 below the cold dust mass inferred from SCUBA observations. Finally, we comment on issues relevant to the possible precursor star and the supernova type.

Dust Destruction in a Non-Radiative Shock in the Cygnus Loop Supernova Remnant

“…However, it is consistent with our earlier findings: for several remnants in the LMC (Borkowski et al 2006;Williams et al 2006) and Kepler's SNR in our Galaxy (Blair et al 2007), the inferred dust-to-gas ratios are invariably lower than the standard values.…”

“…We use dust models employed by us in our previous work with Spitzer data on SNRs in our own Galaxy (Blair et al 2007;Morton et al 2007) and in the Magellanic Clouds (Borkowski et al 2006;Williams et al 2006). These models have been described in sufficient detail in these references, and we elaborate here only on the most recent improvements relevant for the interpretation of Spitzer observations of the Cygnus Loop.…”

“…In the case of four prominent Type Ia * Based on observations made with the Spitzer Space Telescope. remnants in the Large Magellanic Cloud (LMC; Borkowski et al 2006), and Kepler's SNR in our Galaxy (Blair et al 2007), images obtained through the 24 μm and 70 μm bands with the Multiband Imaging Photometer for Spitzer (MIPS) have allowed us to reliably measure the fluxes from the dust associated with fast non-radiative shocks. These measurements provide stringent tests of the models, and have consequently led to a clearer understanding of the dust destruction process and a more accurate estimate of the amount of dust destroyed than had been possible with pre-Spitzer data.…”

Iron: A Key Element for Understanding the Origin and Evolution of Interstellar Dust

“…Observations of remnants such as Kepler, (Blair et al 2007;Williams et al 2012), RCW 86 (Williams et al 2011), SN 1006 (Winkler et al 2013), Tycho Williams et al 2013), and N103B (Williams et al 2014) have shown that all the IR emission from these remnants arises from shocked interstellar dust, with no evidence for any dust associated with the SN ejecta (Gomez et al 2012). A firm upper limit, that is considerably less than 0.1 M e, was put on any dust present in the ejecta of Kepler's SNR (Blair et al 2007). For all practical purposes we can safely conclude that all the Fe produced in SN Ia is returned to the ISM in gaseous form.…”

Origin of the dust emission from Tycho's SNR

“…However, the dust formation in type Ia SNR ejecta has never been observed to date (e.g. Blair et al 2007), while it has been reported for type II SNRs (e.g. Douvion et al 2001;Rho et al 2008;Lee et al 2009;Sibthorpe et al 2010) since the first detection from SN 1987A (Lucy et al 1989;Mosley et al 1989;Wooden 1993).…”