Aims.
The arm tangent direction provides a unique viewing geometry, with a long path in relatively narrow velocity ranges and lines of view that cross the arm perpendicular to its thickness. The ...spiral arm tangent regions are therefore the best directions for studying the interstellar medium within spiral density waves in the Milky Way, probing the internal structure in the arms. We focus here on the gas kinematics and star formation in the Galactic plane zone with longitudes of between 281° and 285.5° and latitudes of between ∼−2.5° and ∼1°, respectively, which contains the Carina arm tangency.
Methods.
The Carina arm tangent direction was observed as part of a velocity-resolved H
α
survey of the southern Milky Way using a scanning Fabry-Perot mounted on a telescope, which makes it possible to obtain data cubes containing kinematic information. Our detailed analysis of the resultant H
α
profiles reveals the presence of several layers of ionized gas with different velocities over the surveyed region. We combine the H
α
data with multi-wavelength information in order to assign velocity and distance to the H
II
regions in the probed area and to study the star-formation activity in the Carina arm tangency.
Results.
We find that the Carina arm tangency is at
l
= 282°, and that it spreads from 2 to 6 kpc with a
V
LSR
range of between −20 and +20 km s
−1
. We deduce an arm width of ∼236 pc. We also probe the star formation on a scale of ∼1 kpc
−2
, showing that the star-formation activity is intermediate in comparison with the quiescient Solar neighborhood and the most active Galactic central molecular zone. From our analysis of the stellar motions extracted from the
Gaia
DR3 catalog, we observe that stars around 2.5 kpc are tracing the trailing and the leading sides of the arm, while stars at greater distances more closely trace the inner part of the arm. In parallel, we studied the H
α
velocity structure of the H
II
regions RCW48 and RCW49 in detail, confirming the expansion velocity of ∼20 km s
−1
for RCW 49 and the double-shell structure of RCW 48, which is in agreement with a wind interaction with a previous mass-loss episode.
Nulling interferometry is a technique providing high angular resolution which is the core of the space missions
Darwin and
TPF. The first objective is to reach a deep degree of starlight cancelation ...in the range 6–20
μm, in order to observe and to characterize the signal from an earth-like planet. Among the numerous technological challenges involved in these missions, the question of the beam combination and wavefront filtering has an important place. A single-mode integrated optics (IO) beam combiner could support both the functions of filtering and the interferometric combination, simplifying the instrumental design. Such a perspective has been explored in this work within the project
Integrated Optics for Darwin (IODA), which aims at developing a first IO combiner in the mid-infrared. The solutions reviewed here to manufacture the combiner here are based on infrared dielectric materials on one side, and on metallic conductive waveguides on the other side. With this work, additional inputs are offered to pursue the investigation on mid-infrared photonics devices.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This paper presents a study of the atmospheric refraction and its effect on the light coupling efficiency in an instrument using single-mode optical fibres. We show the analytical approach which ...allowed us to assess the need to correct the refraction in J and H bands while observing with an 8-m Unit Telescope. We then developed numerical simulations to go further in calculations. The hypotheses on the instrumental characteristics are those of AMBER (Astronomical Multi BEam combineR), the near-infrared focal beam combiner of the Very Large Telescope Interferometric mode, but most of the conclusions can be generalized to other single-mode instruments. We used the software package caos to take into account the atmospheric turbulence effect after correction by the European Southern Observatory system Multi-Application Curvature Adaptive Optics. The optomechanical study and design of the system correcting the atmospheric refraction on AMBER is then detailed. We showed that the atmospheric refraction becomes predominant over the atmospheric turbulence for some zenith angles z and spectral conditions: for z larger than 30° in J band for example. The study of the optical system showed that it allows to achieve the required instrumental performance in terms of throughput in J and H bands. First observations in J band of a bright star, α Cir star, at more than 30° from zenith clearly showed the gain to control the atmospheric refraction in a single-mode instrument, and validated the operating law.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Hα survey of the small Magellanic cloud LE COARER, E; ROSADO, M; GEORGELIN, Y ...
Astronomy and astrophysics (Berlin),
12/1993, Volume:
280, Issue:
2
Journal Article
Peer reviewed
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
7.
A Laboratory Interferometer for VITRUV Jocou, L.; Benisty, M.; Gratier, P. ...
The Power of Optical/IR Interferometry: Recent Scientific Results and 2nd Generation Instrumentation
Book Chapter
We study the role of carrier excitation in driving either heat deposition or non-thermal molecular mobility via electronic relaxation in ultrafast laser-irradiated chalcogenide S-based glasses. We ...show the influence of doping and of the glass thermal history in determining permanent positive and negative refractive index change regimes (type I or type II) discussing the case of Ge 15 As 15 S 70 chalcogenide glass. We also point out material and index engineering approaches in defining large mode area light transport concepts in evanescently-coupled waveguide arrays and their application for building embedded detectors for astronomical measurements.
First AMBER/VLTI Observations of Hot Massive Stars Petrov, R. G.; Millour, F.; Chesneau, O. ...
The Power of Optical/IR Interferometry: Recent Scientific Results and 2nd Generation Instrumentation
Book Chapter
AMBER is the first near infrared focal instrument of the VLTI. It combines three telescopes and produces spectrally resolved interferometric measures. This paper discusses some preliminary results of ...the first scientific observations of AMBER with three Unit Telescopes at medium (1500) and high (12000) spectral resolution. We derive a first set of constraints on the structure of the circumstellar material around the Wolf Rayet γ2 Velorum and the LBV η Carinae.
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