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Register a new userWide Integral-Field Infrared Spectroscopy of the Bright [Fe II] Shell in the Young Supernova Remnant G11.2-0.3
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We present the results of wide integral-field near-infrared (1.0-1.8 um) spectroscopic observations of the southeastern shell of the young core-collapse supernova remnant (SNR) G11.2-0.3. We first construct [Fe II] 1.644 um line images of three bright clumps from the obtained spectral image cubes and compare them with those of other transitions such as [Fe II] 1.257, [Fe II] 1.534 and He I 1.083 um line images. This allows us to estimate the electron density (~ 4,700-9,400 cm^-3) and extinction (Av ~ 16-20 mag) of the shell, including detailed two-dimensional distribution of the properties in the brightest clump, as well as the discovery of a faint high-velocity (~ -440 km/s) component in the clump. Our SNR shock model calculations estimate the preshock number density of ~ 250-500 cm^-3 and shock speed of ~ 80-250 km/s in the [Fe II]-emitting region of the SNR. The comparison between the observed and modelled radial profiles of the line intensities and their ratios reveals that the shell is composed of multiple thin filaments which have been likely formed in episodic mass loss processes of a progenitor star. The discovery of the faint high-velocity component supports the interpretation that the southeastern shell of G11.2-0.3 is mainly composed of circumstellar material with contamination by supernova ejecta and also that its ejected material was expelled primarily in the southeast-northwest direction.
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We present results of a 400-ks Chandra observation of the young shell supernova remnant (SNR) G11.2-0.3, containing a pulsar and pulsar-wind nebula (PWN). We measure a mean expansion rate for the shell since 2000 of 0.0277+/-0.0018% per yr, implying an age between 1400 and 2400 yr, and making G11.2-0.3 one of the youngest core-collapse SNRs in the Galaxy. However, we find very high absorption ($A_V sim 16^m pm 2^m$), confirming near-IR determinations and ruling out a claimed association with the possible historical SN of 386 CE. The PWN shows strong jets and a faint torus within a larger, more diffuse region of radio emission and nonthermal X-rays. Central soft thermal X-ray emission is anticorrelated with the PWN; that, and more detailed morphological evidence, indicates that the reverse shock has already reheated all ejecta and compressed the PWN. The pulsar characteristic energy-loss timescale is well in excess of the remnant age, and we suggest that the bright jets have been produced since the recompression. The relatively pronounced shell and diffuse hard X-ray emission in the interior, enhanced at the inner edge of the shell, indicate that the immediate circumstellar medium into which G11.2-0.3 is expanding was quite anisotropic. We propose a possible origin for G11.2-0.3 in a stripped-envelope progenitor that had lost almost all its envelope mass, in an anisotropic wind or due to binary interaction, leaving a compact core whose fast winds swept previously lost mass into a dense irregular shell, and which exploded as a Type cIIb or Ibc supernova.
We present a high-resolution radio study of the supernova remnant (SNR) G11.2-0.3 using archival VLA data. Spectral tomography is performed to determine the properties of this composite-type SNRs individual components, which have only recently been distinguished through X-ray observations. Our results indicate that the spectral index of the pulsar wind nebula (PWN), or plerion, is alpha_P ~ 0.25. We observe a spectral index of alpha_S ~ 0.56 throughout most of the SNR shell region, but also detect a gradient in alpha in the south-eastern component. We compare the spectral index and flux density with recent single-dish radio data of the source. Also, the radio efficiency and morphological properties of this PWN are found to be consistent with results for other known PWN systems.
We compare recent observations of the supernova remnant G11.2-0.3 taken with the VLA during 2001-02 with images from VLA archives (1984-85) to detect and measure the amount of expansion that has occurred during 17 years. The bright, circular outer shell shows a mean expansion of (0.71 +/- 0.15)% and (0.50 +/- 0.17)%, from 20- and 6-cm data, respectively, which corresponds to a rate of 0.057 +/- 0.012/yr at 20 cm and 0.040 +/- 0.013/yr at 6 cm. From this result, we estimate the age of the remnant to be roughly between 960 and 3400 years old, according to theoretical models of supernova evolution. This is highly inconsistent with the 24000 yr characteristic age of PSR J1811-1925, located at the remnants center, but, rather, is consistent with the time since the historical supernova observed in 386 AD. We also predict that G11.2-0.3 is currently in a pre-Sedov evolutionary state, and set constraints on the distance to the remnant based on Chandra X-ray spectral results.
The extreme infrared (IR) luminosity of local luminous and ultra-luminous IR galaxies (U/LIRGs; 11 < log LIR /Lsun < 12 and log LIR /Lsun > 12, respectively) is mainly powered by star-formation processes triggered by mergers or interactions. While U/LIRGs are rare locally, at z > 1, they become more common, they dominate the star-formation rate (SFR) density, and a fraction of them are found to be normal disk galaxies. Therefore, there must be an evolution of the mechanism triggering these intense starbursts with redshift. To investigate this evolution, we present new optical SWIFT integral field spectroscopic H{alpha}+[NII] observations of a sample of 9 intermediate-z (0.2 < z < 0.4) U/LIRG systems selected from Herschel 250{mu}m observations. The main results are the following: (a) the ratios between the velocity dispersion and the rotation curve amplitude indicate that 10-25% (1-2 out of 8) might be compatible with being isolated disks while the remaining objects are interacting/merging systems; (b) the ratio between un-obscured and obscured SFR traced by H{alpha} and LIR, respectively, is similar in both local and these intermediate-z U/LIRGs; and (c) the ratio between 250{mu}m and the total IR luminosities of these intermediate-z U/LIRGs is higher than that of local U/LIRGs with the same LIR . This indicates a reduced dust temperature in these intermediate-z U/LIRGs. This, together with their already measured enhanced molecular gas content, suggests that the interstellar medium conditions are different in our sample of intermediate-z galaxies when compared to local U/LIRGs.
NuSTAR observed G1.9+0.3, the youngest known supernova remnant in the Milky Way, for 350 ks and detected emission up to $sim$30 keV. The remnants X-ray morphology does not change significantly across the energy range from 3 to 20 keV. A combined fit between NuSTAR and CHANDRA shows that the spectrum steepens with energy. The spectral shape can be well fitted with synchrotron emission from a power-law electron energy distribution with an exponential cutoff with no additional features. It can also be described by a purely phenomenological model such as a broken power-law or a power-law with an exponential cutoff, though these descriptions lack physical motivation. Using a fixed radio flux at 1 GHz of 1.17 Jy for the synchrotron model, we get a column density of N$_{rm H}$ = $(7.23pm0.07) times 10^{22}$ cm$^{-2}$, a spectral index of $alpha=0.633pm0.003$, and a roll-off frequency of $ u_{rm rolloff}=(3.07pm0.18) times 10^{17}$ Hz. This can be explained by particle acceleration, to a maximum energy set by the finite remnant age, in a magnetic field of about 10 $mu$G, for which our roll-off implies a maximum energy of about 100 TeV for both electrons and ions. Much higher magnetic-field strengths would produce an electron spectrum that was cut off by radiative losses, giving a much higher roll-off frequency that is independent of magnetic-field strength. In this case, ions could be accelerated to much higher energies. A search for $^{44}$Ti emission in the 67.9 keV line results in an upper limit of $1.5 times 10^{-5}$ $,mathrm{ph},mathrm{cm}^{-2},mathrm{s}^{-1}$ assuming a line width of 4.0 keV (1 sigma).
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