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تسجيل مستخدم جديدHerschel Observations of the W43 mini-starburst
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Aims: To explore the infrared and radio properties of one of the closest Galactic starburst regions. Methods: Images obtained with the Herschel Space Observatory at wavelengths of 70, 160, 250, 350, and 500 microns using the PACS and SPIRE arrays are analyzed and compared with radio continuum VLA data and 8 micron images from the Spitzer Space Telescope. The morphology of the far-infrared emission is combined with radial velocity measurements of millimeter and centimeter wavelength transitions to identify features likely to be associated with the W43 complex. Results: The W43 star-forming complex is resolved into a dense cluster of protostars, infrared dark clouds, and ridges of warm dust heated by massive stars. The 4 brightest compact sources with L > 1.5 x 10^4 Lsun embedded within the Z-shaped ridge of bright dust emission in W43 remain single at 4 (0.1 pc) resolution. These objects, likely to be massive protostars or compact clusters in early stages of evolution are embedded in clumps with masses of 10^3 to 10^4 Msun, but contribute only 2% to the 3.6 x 10^6 Lsun far-IR luminosity of W43 measured in a 16 by 16 pc box. The total mass of gas derived from the far-IR dust emission inside this region is ~10^6 Msun. Cometary dust clouds, compact 6 cm radio sources, and warm dust mark the locations of older populations of massive stars. Energy release has created a cavity blowing-out below the Galactic plane. Compression of molecular gas in the plane by the older HII region near G30.684-0.260 and the bipolar structure of the resulting younger W43 HII region may have triggered the current mini-star burst.
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Context: Star formation efficiency (SFE) theories are currently based on statistical distributions of turbulent cloud structures and a simple model of star formation from cores. They remain poorly tested, especially at the highest densities. Aims: We
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We present rest-frame optical spectra from the FMOS-COSMOS survey of twelve $z sim 1.6$ textit{Herschel} starburst galaxies, with Star Formation Rate (SFR) elevated by $times$8, on average, above the star-forming Main Sequence (MS). Comparing the H$a
lpha$ to IR luminosity ratio and the Balmer Decrement we find that the optically-thin regions of the sources contain on average only $sim 10$ percent of the total SFR whereas $sim90$ percent comes from an extremely obscured component which is revealed only by far-IR observations and is optically-thick even in H$alpha$. We measure the [NII]$_{6583}$/H$alpha$ ratio, suggesting that the less obscured regions have a metal content similar to that of the MS population at the same stellar masses and redshifts. However, our objects appear to be metal-rich outliers from the metallicity-SFR anticorrelation observed at fixed stellar mass for the MS population. The [SII]$_{6732}$/[SII]$_{6717}$ ratio from the average spectrum indicates an electron density $n_{rm e} sim 1,100 mathrm{cm}^{-3}$, larger than what estimated for MS galaxies but only at the 1.5$sigma$ level. Our results provide supporting evidence that high-$z$ MS outliers are the analogous of local ULIRGs, and are consistent with a major merger origin for the starburst event.
The filament IRDC G035.39--00.33 in the W48 molecular complex is one of the darkest infrared clouds observed by textit{Spitzer}. It has been observed by the PACS (70 and 160,$micron$) and SPIRE (250, 350, and 500,$micron$) cameras of the textit{Hersc
hel} Space Observatory as part of the W48 molecular cloud complex in the framework of the HOBYS key programme. The observations reveal a sample of 28 compact sources (deconvolved FWHM sizes $<$0.3 pc) complete down to $sim$$5 msun$ in G035.39--00.33 and its surroundings. Among them, 13 compact sources are massive dense cores with masses $>$$20 msun$. The cloud characteristics we derive from the analysis of their spectral energy distributions are masses of $20-50 msun$, sizes of 0.1--0.2 pc, and average densities of $2-20 times 10^{5} cmc$, which make these massive dense cores excellent candidates to form intermediate- to high-mass stars. Most of the massive dense cores are located inside the G035.39--00.33 ridge and host IR-quiet high-mass protostars. The large number of protostars found in this filament suggests that we are witnessing a mini-burst of star formation with an efficiency of $sim$15% and a rate density of $sim$$40 msun,$yr$^{-1},$kpc$^{-2}$ within $sim$8 pc$^2$, a large area covering the full ridge. Part of the extended SiO emission observed towards G035.39--00.33 is not associated with obvious protostars and may originate from low-velocity shocks within converging flows, as advocated by previous studies.
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We present Herschel/HIFI observations of fourteen water lines in W43-MM1, a massive protostellar object in the luminous star cluster-forming region W43. We analyze the gas dynamics from the line profiles using Herschel-HIFI observations (WISH-KP) of
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