118400768
S IV In The NGC 5253 Supernebula: Ionized Gas Kinematics At High Resolution
The nearby dwarf starburst galaxy NGC 5253 hosts a deeply embedded radio-infrared supernebula excited by thousands of O stars. We have observed this source in the 10.5 {mu}m line of S{sup +3} at 3.8 km s{sup -1} spectral and 1.''4 spatial resolution, using the high-resolution spectrometer TEXES on the IRTF. The line profile cannot be fit well by a single Gaussian. The best simple fit describes the gas with two Gaussians, one near the galactic velocity with FWHM 33.6 km s{sup -1} and another of similar strength and FWHM 94 km s{sup -1} centered {approx}20 km s{sup -1} to the blue. This suggests a model for the supernebula in which gas flows toward us out of the molecular cloud, as in a 'blister' or 'champagne flow' or in the H II regions modelled by Zhu.
118849324
NGC 4102: High-Resolution Infrared Observations Of A Nuclear Starburst Ring
The composite galaxy NGC 4102 hosts a LINER nucleus and a starburst. We mapped NGC 4102 in the 12.8 μm line of [Ne II], using the echelon spectrometer TEXES on the NASA IRTF, to obtain a data cube with 15 spatial, and 25 km s–1 spectral, resolution. Combining near-infrared, radio, and the [Ne II] data shows that the extinction to the starburst is substantial, more than 2 mag at the K band, and that the neon abundance is less than half solar. We find that the star formation in the nuclear region is confined to a rotating ring or disk of 43 (~300 pc) diameter, inside the inner Lindblad resonance. This region is an intense concentration of mass, with a dynamical mass ~3 × 109 M ☉, and of star formation. The young stars in the ring produce the [Ne II] flux reported by Spitzer for the entire galaxy. The mysterious blue component of line emission detected in the near-infrared is also seen in [Ne II]; it is not a normal active galactic nucleus outflow.
24291153
An extragalactic supernebula confined by gravity
Little is known about the origins of globular clusters, which contain hundreds of thousands of stars in a volume only a few light years across. Radiation pressure and winds from luminous young stars should disperse the star-forming gas and disrupt the formation of the cluster. Globular clusters in our Galaxy cannot provide answers; they are billions of years old. Here we report the measurement of infrared hydrogen recombination lines from a young, forming super star cluster in the dwarf galaxy NGC5253. The lines arise in gas heated by a cluster of about one million stars, including 4,000–6,000 massive, hot ‘O’ stars. It is so young that it is still enshrouded in gas and dust, hidden from optical view. The gases within the cluster seem bound by gravity, which may explain why the windy and luminous O stars have not yet blown away those gases. Young clusters in ‘starbursting’ galaxies in the local and distant Universe may also be gravitationally confined and cloaked from view.
15435454
RADIO-INFRARED SUPERNEBULAE IN II Zw 40
We report subarcsecond-resolution Very Large Array and Keck mid-infrared imaging of the dwarf starburst galaxy II Zw 40. II Zw 40 contains a bright compact thermal radio and infrared source with all the characteristics of a collection of dense H ii regions ionized by at least 14,000 O stars. The supernebula is revealed to consist of multiple sources within an envelope of weaker emission. The radio emission is dominated by free-free emission at 2 cm, and the spectrum of this emission appears to be rising. This suggests that the free-free emission is optically thick at 2 cm and that the individual H ii regions are � 1 pc in size. This complex of ‘‘ supernebulae ’’ dominates the total infrared luminosity of II Zw 40, although the radio source is less than � 150 pc in diameter. Multiple super–star clusters appear to be forming here, the much larger analogs of large Galactic H ii region complexes.
1155749
High Resolution Radio Maps of Four Nearby Spiral Galaxies
We report subarcsecond-resolution VLA imaging of the centers of four nearby spiral galaxies: IC 342, Maffei II, NGC 2903, and NGC 6946. In each galaxy, 7 - 12 compact radio continuum sources were identified within the central ∼ 15 ′′ × 15 ′′ . Slightly over half of the compact sources appear to be H ii regions with flat or positive spectral indices (�> ∼ −0.1). The H ii regions with rising spectra are optically thick at centimeter wavelengths, and thus dense (ni ∼ 10 4 cm −3 ) and young. The largest of these H ii regions require the excitation of 500 - 800 O stars, within regions of only few parsecs extent. These clusters approach the sizes expected for globular clusters.
7473856
Properties of hot stars in the Wolf-Rayet galaxy NGC 5253 from ISO-SWS spectroscopy
ISO-SWS spectroscopy of the Wolf--Rayet galaxy NGC 5253 is presented, and analysed to provide estimates of its hot young star population. Our approach differs from previous investigations in that we are able to distinguish between the regions in which different infrared fine-structure lines form, using complementary ground-based observations. The high-excitation nebular [S IV] emission is formed in a very compact region, which we attribute to the central super-star nucleus, and lower excitation [Ne III] nebular emission originates in the galactic core. We use photoionization modelling coupled with the latest theoretical O-star flux distributions to derive effective stellar temperatures and ionization parameters of Teff≥ 38 kK, log Q ∼ 8.25 for the compact nucleus, with Teff∼ 35 kK, log Q ≤ 8 for the larger core. Results are supported by more sophisticated calculations using evolutionary synthesis models. We assess the contribution that Wolf--Rayet stars may make to highly ionized nebular lines (e.g. [O IV]). From our Brα flux, the 2-arcsec nucleus contains the equivalent of approximately 1000 O7 V star equivalents and the starburst there is 2--3 Myr old; the 20-arcsec core contains about 2500 O7 V star equivalents, with a representative age of ∼5 Myr. The Lyman ionizing flux of the nucleus is equivalent to that of the 30 Doradus region. These quantities are in good agreement with the observed mid-infrared dust luminosity of 7.8 × 108 L⊙. Since this structure of hot clusters embedded in cooler emission may be common in dwarf starbursts, observing a galaxy solely with a large aperture may result in confusion. Neglecting the spatial distribution of nebular emission in NGC 5253 implies `global' stellar temperatures (or ages) of 36 kK (4.8 Myr) and 39 kK (2.9 or 4.4 Myr) from the observed [Ne III/ II] and [S IV/ III] line ratios, assuming logQ=8.
53662967
Supersymmetry of AdS and flat IIB backgrounds
A bstractWe present a systematic description of all warped AdSn ×wM10−n and ℝn−1,1×wM10−n$$ {\mathbb{R}}^{n-1,1}{\times}_w{M}^{10-n} $$ IIB backgrounds and identify the a priori number of supersymmetries N preserved by these solutions. In particular, we find that the AdSn backgrounds preserve N=2n2k$$ N={2}^{\left[\frac{n}{2}\right]}k $$ for n ≤ 4 and N=2n2+1k$$ N={2}^{\left[\frac{n}{2}\right]+1}k $$ for 4 < n ≤ 6 supersymmetries and for k∈ℕ+$$ k\in {\mathbb{N}}_{+} $$ suitably restricted. In addition under some assumptions required for the applicability of the maximum principle, we demonstrate that the Killing spinors of AdSn backgrounds can be identified with the zero modes of Dirac-like operators on M10−n establishing a new class of Lichnerowicz type theorems. Furthermore, we adapt some of these results to ℝn−1,1×wM10−n$$ {\mathbb{R}}^{n-1,1}{\times}_w{M}^{10-n} $$ backgrounds with fluxes by taking the AdS radius to infinity. We find that these backgrounds preserve N=2n2k$$ N={2}^{\left[\frac{n}{2}\right]}k $$ for 2 < n ≤ 4 and N=2n+12k$$ N={2}^{\left[\frac{n+1}{2}\right]}k $$ for 4 < n ≤ 7 supersymmetries. We also demonstrate that the Killing spinors of AdSn ×wM10−n do not factorize into Killing spinors on AdSn and Killing spinors on M10−n.