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تسجيل مستخدم جديدEta Carinae & the Homunculus: Far Infrared, Sub-millimeter Spectral Lines
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The evolved massive binary star Eta Carinae underwent eruptive mass loss events that formed the complex bi-polar Homunculus nebula harboring tens of solar masses of unusually nitrogen-rich gas and dust. Despite expectations for the presence of a significant molecular component to the gas, detections have been observationally challenged by limited access to the far-infrared and the intense thermal continuum. A spectral survey of the atomic and rotational molecular transitions was carried out with the Herschel Space Observatory, revealing a rich spectrum of broad emission lines originating in the ejecta. Velocity profiles of selected PACS lines correlate well with known substructures: H I in the central core; NH and weak [C II] within the Homunculus; and [N II] emissions in fast-moving structures external to the Homunculus. We have identified transitions from [O I], H I, and 18 separate light C- and O-bearing molecules including CO, CH, CH+, and OH, and a wide set of N-bearing molecules, NH, NH+, N2H+, NH2, NH3, HCN, HNC, CN, and N2H+. Half of these are new detections unprecedented for any early-type massive star environment. A very low ratio [12C/13C] LE 4 is estimated from five molecules and their isotopologues. We demonstrate that non-LTE effects due to the strong continuum are significant. Abundance patterns are consistent with line formation in regions of carbon and oxygen depletions with nitrogen enhancements, reflecting an evolved state of the erupting star with efficient transport of CNO-processed material to the outer layers. The results offer many opportunities for further observational and theoretical investigations of the molecular chemistry under extreme physical and chemical conditions around massive stars in their final stages of evolution.
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We investigate, using the modeling code SHAPE, the three-dimensional structure of the bipolar Homunculus nebula surrounding Eta Carinae, as mapped by new ESO VLT/X-Shooter observations of the H2 $lambda=2.12125$ micron emission line. Our results reve
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elected from the Herschel Multi-tiered Extragalactic Survey and the SCUBA-2 Cosmology Legacy Survey, respectively. Their precise locations are based on the interferometry data from the Atacama Large Millimeter/submillimeter Array and the Very Large Array. The vast majority of these objects are at $0.1lesssim zlesssim 3$. While the SMGs do not constitute a subset of the FIRGs in our selection due to the signal-to-noise ratio thresholds, SMGs can be regarded as the population at the high-redshift tail of FIRGs. Most of our FIRGs/SMGs have total infrared luminosity ($L_{rm IR}$) in the regimes of luminous and ultra-luminous infrared galaxies (LIRGs, $L_{rm IR} = 10^{11-12}L_odot$; ULIRGs, $L_{rm IR}>10^{12}L_odot$). The hosts of the SMG ULIRGs, FIRG ULIRGs and FIRG LIRGs are of sufficient numbers to allow for detailed analysis, and they are only modestly different in their stellar masses. Their morphological types are predominantly disk galaxies (type D) and irregular/interacting systems (type Irr/Int). There is a morphological transition at $zapprox 1.25$ for the FIRG ULIRG hosts, above which the Irr/Int galaxies dominate and below which the D and the Irr/Int galaxies have nearly the same contributions. The SMG ULIRG hosts seem to experience a similar transition. This suggests a shift in the relative importance of galaxy mergers/interactions versus secular gas accretions in normal disk galaxies as the possible triggering mechanisms of ULIRGs. The FIRG LIRG hosts are predominantly D galaxies over $z=0.25-1.25$ where they are of sufficient statistics.
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3) inversion transition made with the Australia Telescope Compact Array reveal emission at locations where infrared H2 emission had been detected previously, near the strongest dust emission in the core of the Homunculus. We also detect ammonia emission from the so-called ``strontium filament in the equatorial disk. The presence of NH3 around eta Car hints that molecular shells around some Wolf-Rayet stars could have originated in prior LBV eruptions, rather than in cool red supergiant winds or the ambient interstellar medium. Combined with the lack of any CO detection, NH3 seems to suggest that the Homunculus is nitrogen rich like the ionized ejecta around eta Car. It also indicates that the Homunculus is a unique laboratory in which to study unusual molecule and dust chemistry, as well as their rapid formation in a nitrogen-rich environment around a hot star. We encourage future observations of other transitions like NH3 (1,1) and (2,2), related molecules like N2H+, and renewed attempts to detect CO.
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