Search

IRAS 15099-5856 in the young supernova remnant (SNR) MSH 15-52 is the first and only SNR-associated object with crystalline silicate dust detected so far, although its nature and the origin of the crystalline silicate are still unclear. In this paper, we present high-resolution mid-infrared (MIR) imaging observations of the bright central compact source IRS1 of IRAS 15099-5856 to study the spatial distributions of gas and dust and the analysis of its Spitzer MIR spectrum to explore the origin of IRS1. The MIR images obtained with the T-ReCS attached on the Gemini South telescope show a complicated, inhomogeneous morphology of IRS1 with bright clumps and diffuse emission in [Ne II] 12.81 $\mu$m and Qa 18.30 $\mu$m, which confirms that IRS1 is an extended source externally heated by the nearby O star Muzzio 10, a candidate for the binary companion of the progenitor star. The Spitzer MIR spectrum reveals several ionic emission lines including a strong [Ne II] 12.81 $\mu$m line, but no hydrogen line is detected. We model the spectrum using the photoionization code CLOUDY with varying elemental composition. The elemental abundance of IRS1 derived from the model is close to that of SN ejecta with depleted hydrogen and enhanced metals, particularly neon, argon, and iron. Our results imply that IRS1 originates from the SN ejecta and suggest the possibility of the formation of crystalline silicate in newly-formed SN dust., Comment: 18 pages, 9 figures, accepted for publication in The Astrophysical Journal

Most stars form in multiple star systems. For a better understanding of their formation processes, it is important to resolve the individual protostellar components and the surrounding envelope and disk material at the earliest possible formation epoch because the formation history can be lost in a few orbital timescales. Here we present the ALMA observational results of a young multiple protostellar system, IRAS 04239+2436, where three well-developed large spiral arms were detected in the shocked SO emission. Along the most conspicuous arm, the accretion streamer was also detected in the SO$_2$ emission. The observational results are complemented by numerical magneto-hydrodynamic simulations, where those large arms only appear in magnetically weakened clouds. The numerical simulations also suggest that the large triple spiral arms are the result of gravitational interactions between compact triple protostars and the turbulent infalling envelope., Comment: Accepted for publication in ApJ

We investigate the effects of winds on the observational properties of Type Ib and Ic supernova (SN Ib/Ic) progenitors using spectral models constructed with the non-LTE stellar atmospheric code CMFGEN. We consider SN Ib/Ic progenitor models of the final mass range of 2.16 -- 9.09~$M_\odot$ having different surface temperatures and chemical compositions, and calculate the resulting spectra for various wind mass-loss rates and wind terminal velocities. We find that the progenitors having an optically thick wind would become brighter in the optical for a higher mass-loss rate (or a lower wind terminal velocity), because of the formation of the photosphere in the extended wind matter and the contribution from free-free and line emissions from the wind. As a result, for the standard Wolf-Rayet wind mass-loss rate, helium-deficient compact SN Ic progenitors would be brighter in the optical by $\sim$3 mag compared to the case without the wind effects. We also find that the color dependence on the photospheric temperature is non-monotonic because of the wind effects. Our results imply that inferring the progenitor mass, bolometric luminosity and effective temperature from the optical observation using the standard stellar evolution model prediction can be misleading. By comparing our fiducial model predictions with the detection limits of the previous SN Ib/Ic progenitor searches, we conclude that a deep search with an optical absolute magnitude larger than $\sim -4$ is needed to directly identify most of the ordinary SN Ib/Ic progenitors. We discuss implications of our results for the observed SN Ib/Ic progenitor candidates for iPTF13bvn, SN 2019yvr and SN 2017ein., Comment: 32 pages, 18 figures, 5 tables ; accepted for publication in ApJ

Cassiopeia A is a nearby young supernova remnant that provides a unique laboratory for the study of core-collapse supernova explosions. Cassiopeia A is known to be a Type IIb supernova from the optical spectrum of its light echo, but the immediate progenitor of the supernova remains uncertain. Here we report results of near-infrared, high-resolution spectroscopic observations of Cassiopeia A where we detected the pristine circumstellar material of the supernova progenitor. Our observations revealed a strong emission line of iron (Fe) from a circumstellar clump that has not yet been processed by the supernova shock wave. A comprehensive analysis of the observed spectra, together with an HST image, indicates that the majority of Fe in this unprocessed circumstellar material is in the gas phase, not depleted onto dust grains as in the general interstellar medium. This result is consistent with a theoretical model of dust condensation in material that is heavily enriched with CNO-cycle products, supporting the idea that the clump originated near the He core of the progenitor. It has been recently found that Type IIb supernovae can result from the explosion of a blue supergiant with a thin hydrogen envelope, and our results support such a scenario for Cassiopeia A., Comment: 18 pages, 7 figures

We present a long-exposure (~10 hr) image of the supernova (SN) remnant Cassiopeia A (Cas A) obtained with the UKIRT 3.8-m telescope using a narrow band filter centered at 1.644 um emission. The passband contains [Fe II] 1.644 um and [Si I] 1.645 um lines, and our `deep [Fe II]+[Si I] image' provides an unprecedented panoramic view of Cas A, showing both shocked and unshocked SN ejecta together with shocked circumstellar medium at subarcsec (~0.7 arcsec or 0.012 pc) resolution. The diffuse emission from the unshocked SN ejecta has a form of clumps, filaments, and arcs, and their spatial distribution correlates well with that of the Spitzer [Si II] infrared emission, suggesting that the emission is likely due to [Si I] line not [Fe II] line as in shocked material. The structure of the optically-invisible western area of Cas A is clearly seen for the first time. The area is filled with many Quasi-Stationary Flocculi (QSFs) and fragments of the disrupted ejecta shell. We suggest that the anomalous radio properties in this area could be due to the increased number of such dense clumps. We identified 309 knots in the deep [Fe II]+[Si I] image and classified them into QSFs and fast-moving knots (FMKs). The total H+He mass of QSFs is ~0.23 Msun, implying that the mass fraction of dense clumps in the progenitor's red-supergiant wind is 4--13%. The spatial distribution of QSFs suggests that there had been a highly asymmetric mass loss $10^4$--$10^5$ yr before the SN explosion. The mass of the [Fe II] line-emitting, shocked dense Fe ejecta is ~3x$10^{-5}$ Msun. The comparison with the ionic S-line dominated Hubble Space Telescope WFC3/IR image suggests that the outermost FMKs in the southeastern area are Fe-rich., Comment: 36 pages, 13 figures, ApJ in press

We present a parsec-scale molecular hydrogen (H$_2$ 1-0 S(1) at 2.12~\micron) outflow discovered from the UKIRT Widefield Infrared Survey for H$_2$. The outflow is located in the infrared dark cloud core MSXDC G053.11+00.05 MM1 at 1.7 kpc and likely associated with two young stellar objects (YSOs) at the center. The overall morphology of the outflow is bipolar along the NE-SW direction with a brighter lobe to the southwest, but the detailed structure consists of several flows and knots. With the total length of $\sim$1 pc, the outflow luminosity is fairly high with $L_{\rm H_{2}} > 6~L_{\sun}$, implying a massive outflow-driving YSO if the entire outflow is driven by a single source. The two putative driving sources, located at the outflow center, show photometric variability of $\gtrsim$1 mag in {\it H}- and {\it K}-bands. This, with their early evolutionary stage from spectral energy distribution (SED) fitting, indicates that both are capable of ejecting outflows and may be eruptive variable YSOs. The YSO masses inferred from SED fitting are $\sim$10~$M_{\sun}$ and $\sim$5~$M_{\sun}$, suggesting the association of the outflow with massive YSOs. The geometrical morphology of the outflow is well explained by the lower mass YSO by assuming a single source origin, but without kinematic information, the contribution from the higher mass YSO cannot be ruled out. Considering star formation process by fragmentation of a high-mass core into several lower mass stars, we also suggest the possible presence of another, yet-undetected driving source deeply embedded in the core., Comment: 28 pages, 8 figures, accepted for publication in the Astrophysical Journal

[Fe II] emission lines are prominent in the infrared (IR), and they are important diagnostic tools for radiative atomic shocks. We investigate the emission characteristics of [Fe II] lines using a shock code developed by Raymond (1979) with updated atomic parameters. We first review general characteristics of IR [Fe II] emission lines from shocked gas, and derive [Fe II] line fluxes as a function of shock speed and ambient density. We have compiled the available IR [Fe II] line observations of interstellar shocks and compare them to the ratios predicted from our model. The sample includes both young and old supernova remnants in the Galaxy and the Large Magellanic Cloud and several Herbig-Haro objects. We find that the observed ratios of IR [Fe II] lines generally fall on our grid of shock models, but the ratios of some mid-infrared lines, e.g., [Fe II] 35.35 um/[Fe II] 25.99 um, [Fe II] 5.340 um/[Fe II] 25.99 um, and [Fe II] 5.340 um/[Fe II] 17.94 um, are significantly offset from our model grid. We discuss possible explanations and conclude that the uncertainty in atomic rates might be the major source of uncertainty, while uncertainties in the shock modeling and the observations certainly exist., Comment: 14 pages, 12 figures, submitted to the Journal of the Korean Astronomical Society

Recent high-resolution infrared space missions have revealed supernova remnants (SNRs) of diverse morphology in infrared (IR) dust emission that is often very different from their X-ray appearance. The observed range of infrared-to-X-ray (IRX) flux ratios of SNRs are also wide. For a sample of 20 Galactic SNRs, we obtain their IR and X-ray properties and investigate the physical causes for such large differences. We find that the observed IRX flux ratios ($R_{IRX.obs}$) are related to the IRX morphology, with SNRs with the largest $R_{IRX,obs}$ showing anticorrelated IRX morphology. By analyzing the relation of $R_{IRX,obs}$ to X-ray and IR parameters, we show that the $R_{IRX,obs}$ of some SNRs agree with theoretical ratios of SNR shocks in which dust grains are heated and destroyed by collisions with plasma particles. For the majority of SNRs, however, $R_{IRX,obs}$ values are either significantly smaller or significantly larger than the theoretical ratios. The latter SNRs have relatively low dust temperatures. We discuss how the natural and/or environmental properties of SNRs could have affected the IRX flux ratios and the IRX morphology of these SNRs. We conclude that the SNRs with largest $R_{IRX,obs}$ are probably located in dense environment and that their IR emission is from dust heated by shock radiation rather than by collisions. Our result suggests that the IRX flux ratio, together with dust temperature, can be used to infer the nature of unresolved SNRs in external galaxies., Comment: 30 pages, 9 figures, Accepted for publication in the Astrophysical Journal on February 11, 2016

In several recent observational studies on Type Ib/c supernovae (SNe Ib/c), the inferred ejecta masses have a peak value of 2.0 -- 4.0 $M_\odot$, in favor of the binary scenario for their progenitors rather than the Wolf-Rayet star scenario. To investigate the observational properties of relatively low-mass helium stars in binary systems as SN Ib/c progenitors, we constructed atmospheric models with the non-LTE radiative transfer code CMFGEN, using binary star evolution models. We find that these helium stars can be characterized by relatively narrow helium emission lines if the mass-loss rate during the final evolutionary phase is significantly enhanced as implied by many SN Ib/c observations. The optical brightness of helium star progenitors can be meaningfully enhanced with a strong wind for $M \gtrsim 4.4 M_\odot$, but hardly affected or slightly weakened for relatively low-mass of $\sim 3.0 M_\odot$, compared to the simple estimate using blackbody approximation. We further confirm the previous suggestion that the optical brightness would be generally higher for a less massive SN Ib/c progenitor. In good agreement with previous studies, our results indicate that the optical magnitudes and colors of the recently detected progenitor of the SN Ib iPTF13bvn can be well explained by a binary progenitor with a final helium star mass of about 3.0 -- 4.4 $M_\odot$., Comment: 14 pages, 7 figures, 3 tables, accepted for publication in ApJ

We present star formation activity in the infrared dark cloud (IRDC) G53.2, a remarkable IRDC located at Galactic coordinates $(l,b)\sim(53^{\circ}.2,\,0^{\circ}.0)$ based on the census of young stellar object (YSO) candidates. IRDC G53.2 was previously identified as several IRDCs in mid-IR images, but it is in fact a long ($\gtrsim$45 pc) cloud, well consistent with a CO cloud at $v\sim23$ \kms\ (or at $d\sim$1.7 kpc). We present a point-source catalog of IRDC G53.2 that contains $\sim$370 sources from our photometry of the {\it Spitzer} MIPS 24 \um\ data and Galactic Legacy Infrared Mid-Plane Survey Extraordinaire Catalog. The classification of the identified sources based on their spectral index and control field analysis to remove field star contamination reveals that IRDC G53.2 is an active star-forming region with $\sim$300 YSO candidates. We compare the YSO classification based on spectral index, mid-IR colors, and the wavelength range used, which results in consistent classification, except for flat-spectrum objects, with some ambiguity between Class I and II. Comparison of the YSO population in IRDC G53.2 with those of other nearby star-forming clusters indicates that they are similar in age; on the other hand, stronger association with mid-IR stellar sources in IRDC G53.2 compared with other IRDCs indicates that IRDC G53.2 is at a later evolutionary stage among IRDCs. Spatial distribution of the YSO candidates in IRDC G53.2 shows a good correlation with $^{13}$CO column density and far-IR emission, and earlier-class objects tend to be more clustered in the regions with higher density., Comment: 42 pages, 11 figures, 8 tables; accepted for publication in ApJ