Spitzer
                    and
                    Hubble Space Telescope
                    Constraints on the Physical Properties of the
                    z
                     ~ 7 Galaxy Strongly Lensed by A2218

ABSTRACT We present an optical analysis of 55 members of R136, the central cluster in the Tarantula Nebula of the Large Magellanic Cloud. Our sample was observed with STIS aboard the Hubble Space Telescope, is complete down to about 40 M⊙, and includes seven very massive stars with masses over 100 M⊙. We performed a spectroscopic analysis to derive their physical properties. Using evolutionary models, we find that the initial mass function of massive stars in R136 is suggestive of being top-heavy with a power-law exponent γ ≈ 2 ± 0.3, but steeper exponents cannot be excluded. The age of R136 lies between 1 and 2 Myr with a median age of around 1.6 Myr. Stars more luminous than log L/L⊙ = 6.3 are helium enriched and their evolution is dominated by mass-loss, but rotational mixing or some other form of mixing could be still required to explain the helium composition at the surface. Stars more massive than 40 M⊙ have larger spectroscopic than evolutionary masses. The slope of the wind–luminosity relation assuming unclumped stellar winds is 2.41 ± 0.13 which is steeper than usually obtained (∼1.8). The ionizing ($\log Q_0\, [{\rm ph/s}] = 51.4$) and mechanical ($\log L_{\rm SW}\, [{\rm erg/s}] = 39.1$) output of R136 is dominated by the most massive stars ($\gt 100\, \mathrm{ M}_{\odot }$). R136 contributes around a quarter of the ionizing flux and around a fifth of the mechanical feedback to the overall budget of the Tarantula Nebula. For a census of massive stars of the Tarantula Nebula region, we combined our results with the VLT-FLAMES Tarantula Survey plus other spectroscopic studies. We observe a lack of evolved Wolf–Rayet stars and luminous blue and red supergiants.

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Hubble Space Telescope Observations of [O III] Emission in Nearby QSO2s: Physical Properties of the Ionised Outflows

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3239 ◽

2020 ◽

Author(s):

Anna Trindade Falcão ◽

S B Kraemer ◽

T C Fischer ◽

D M Crenshaw ◽

M Revalski ◽

...

Keyword(s):

Physical Properties ◽

Emission Line ◽

Hubble Space Telescope ◽

Radial Distance ◽

Flow Rates ◽

Space Telescope ◽

Bolometric Luminosity ◽

Mass Outflow ◽

Peak Outflow ◽

Imaging Spectrograph

Abstract We use Hubble Space Telescope (HST)/ Space Telescope Imaging Spectrograph (STIS) long-slit G430M and G750M spectra to analyse the extended [O III] λ5007 emission in a sample of twelve nearby (z >0.12) luminous (Lbol > 1.6 × 1045 erg s−1) QSO2s. The purpose of the study is to determine the properties of the mass outflows of ionised gas and their role in AGN feedback. We measure fluxes and velocities as functions of radial distances. Using Cloudy models and ionising luminosities derived from [O III] λ5007, we are able to estimate the densities for the emission-line gas. From these results, we derive masses of [O III]-emitting gas, mass outflow rates, kinetic energies, kinetic luminosities, momenta and momentum flow rates as a function of radial distance for each of the targets. For the sample, masses are several times 103M⊙ − 107M⊙ and peak outflow rates are 9.3 × 10−3M⊙ yr−1 to 10.3 M⊙ yr−1. The peak kinetic luminosities are 3.4 × 10−8 to 4.9 × 10−4 of the bolometric luminosity, which does not approach the 5.0 × 10−3 - 5.0 × 10−2 range required by some models for efficient feedback. For Mrk 34, which has the largest kinetic luminosity of our sample, in order to produce efficient feedback there would have to be 10 times more [O III]-emitting gas than we detected at its position of maximum kinetic luminosity. Three targets show extended [O III] emission, but compact outflow regions. This may be due to different mass profiles or different evolutionary histories.

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