96 research outputs found
New transit observations for HAT-P-30 b, HAT-P-37 b, TrES-5 b, WASP-28 b, WASP-36 b, and WASP-39 b
We present new transit light curves for planets in six extrasolar planetary
systems. They were acquired with 0.4-2.2 m telescopes located in west Asia,
Europe, and South America. When combined with literature data, they allowed us
to redetermine system parameters in a homogeneous way. Our results for
individual systems are in agreement with values reported in previous studies.
We refined transit ephemerides and reduced uncertainties of orbital periods by
a factor between 2 and 7. No sign of any variations in transit times was
detected for the planets studied.Comment: Submitted to Acta Astronomic
Modelling and control of a variable-length flexible beam on inspection ground robot
Stabilising an inverted pendulum on a cart is a well-known control problem. This paper proposes the mechanical and control design for solving the oscillation problem of a variable-length flexible beam mounted on a mobile robot. The system under consideration is the robot PovRob, used at the European Organization for Nuclear Research (CERN) for visual and remote inspection tasks of particle accelerators. The flexible beam mounted on the robot houses cameras and sensors. The innovative aspect of the approach concerns the use of actuated masses mounted at the end of the rod, which induces an impulsive moment due to their inertia and angular acceleration. The modelling of the flexible rod has been suitably simplified in a lumped-parameter system, with dynamic parameters related to the rod’s flexibility. A linearisation of the dynamic model allows a linear-quadratic control to stabilise the system. Experimental results support the identification and the validation of the dynamic model, while simulation results evaluate the performances of the designed control law
Building the Largest Spectroscopic Sample of Ultracompact Massive Galaxies with the Kilo Degree Survey
Ultracompact massive galaxies (ucmgs), i.e., galaxies with stellar masses M∗ > 8× 10-10 M⊙ and effective radii R e< 1.5 kpc, are very rare systems, in particular at low and intermediate redshifts. Their origin as well as their number density across cosmic time are still under scrutiny, especially because of the paucity of spectroscopically confirmed samples. We have started a systematic census of ucmg candidates within the ESO Kilo Degree Survey, together with a large spectroscopic follow-up campaign to build the largest possible sample of confirmed ucmgs. This is the third paper of the series and the second based on the spectroscopic follow-up program. Here, we present photometrical and structural parameters of 33 new candidates at redshifts 0.15≲ z≲ 0.5 and confirm 19 of them as ucmgs, based on their nominal spectroscopically inferred M and R e. This corresponds to a success rate of ∼ 58%, nicely consistent with our previous findings. The addition of these 19 newly confirmed objects allows us to fully assess the systematics on the system selection-and to finally reduce the number density uncertainties. Moreover, putting together the results from our current and past observational campaigns and some literature data, we build the largest sample of ucmgs ever collected, comprising 92 spectroscopically confirmed objects at 0.1≲ z≲ 0.5. This number raises to 116, allowing for a 3σ tolerance on the M∗ and Re thresholds for the ucmg definition. For all these galaxies, we have estimated the velocity dispersion values at the effective radii, which have been used to derive a preliminary mass-velocity dispersion correlation
INSPIRE: INvestigating Stellar Population in RElics: I. Survey presentation and pilot study
[Context] Massive elliptical galaxies are thought to form through a two-phase process. At early times (z > 2), an intense and fast starburst forms blue and disk-dominated galaxies. After quenching, the remaining structures become red, compact, and massive (i.e. red nuggets). Then, a time-extended second phase, which is dominated by mergers, causes structural evolution and size growth. Given the stochastic nature of mergers, a small fraction of red nuggets survive, without any interaction, massive and compact until today: these are relic galaxies. Since this fraction depends on the processes dominating the size growth, counting relics at low-z is a valuable way of disentangling between different galaxy evolution models. [Aims] In this paper, we introduce the INvestigating Stellar Population In RElics (INSPIRE) Project, which aims to spectroscopically confirm and fully characterise a large number of relics at 0:1z0:5. We focus here on the first results based on a pilot study targeting three systems, representative of the whole sample. [Methods] For these three candidates, we extracted 1D optical spectra over an aperture of r = 0:4000, which comprises 30% of the galaxies’ light, and we obtained the line-of-sight integrated stellar velocity and velocity dispersion. We also inferred the stellar [/Fe] abundance from line-index measurements and mass-weighted age and metallicity from full-spectral fitting with single stellar population models. [Results] Two galaxies have large integrated stellar velocity dispersion values (250 km s), confirming their massive nature. They are populated by stars with super-solar metallicity and [/Fe]. Both objects have formed 80% of their stellar mass within a short (0:5:0 Gyr) initial star formation episode occurred only 1 Gyr after the Big Bang. The third galaxy has a more extendedstar formation history and a lower velocity dispersion. Thus we confirm two out of three candidates as relics. [Conclusions] This paper is the first step towards assembling the final INSPIRE catalogue that will set stringent lower limits on the number density of relics at z0:5, thus constituting a benchmark for cosmological simulations, and their predictions on number densities, sizes, masses, and dynamical characteristics of these objects.CS is supported by a Hintze Fellowship at the Oxford Centre for Astrophysical Surveys, which is funded through generous support from the Hintze Family Charitable Foundation. C.S. is also very grateful to Ortwin Gerhard and his ?Dynamics Group? at the Max-Planck-Institut f?r Extraterrestrische Physik (MPE, Garching by Munich) for interesting and constructive discussions. C.T., A.G., L.H. and S.Z. acknowledge funding from the INAF PRIN-SKA 2017 programme 1.05.01.88.04. G.D. acknowledges support from CONICYT project Basal AFB-170002. AFM has received financial support through the Postdoctoral Junior Leader Fellowship Programme from La Caixa Banking Foundation (LCF/BQ/LI18/11630007). N.R.N. acknowledges financial support from the One hundred top talent programme of Sun Yat-sen University, Grant N. 71000-18841229. D.S. is a member of the International Max Planck Research School (IMPRS) for Astronomy and Astrophysics at the Universities of Bonn and Cologne
INSPIRE: INvestigating Stellar Population In RElics -- I. Survey presentation and pilot program
Massive ETGs are thought to form through a two-phase process. At early times,
an intense and fast starburst forms blue and disk-dominated galaxies. After
quenching, the remaining structures become red, compact and massive, i.e., 'red
nuggets'. Then, a time-extended second phase which is dominated by mergers,
causes structural evolution and size growth. Given the stochastic nature of
mergers, a small fraction of red nuggets survives, without any interaction,
massive and compact until today: relic galaxies. Since this fraction depends on
the processes dominating the size growth, counting relics at low-z is a
valuable way to disentangle between different galaxy evolution models. In this
paper, we introduce the INvestigating Stellar Population In RElics (INSPIRE)
Project, that aims at spectroscopically confirming and fully characterizing a
large number of relics at 0.1<z<0.5. We focus here on the first results based
on a pilot program targeting three systems, representative of the whole sample.
For these, we extract 1D optical spectra over an aperture comprising ~30 % of
the galaxies light, and obtain line-of-sight integrated stellar velocity and
velocity dispersion. We also infer the stellar [/Fe] abundance from
line-index measurements and mass-weighted age and metallicity from
full-spectral fitting with single stellar population models. Two galaxies have
large integrated stellar velocity dispersion values, confirming their massive
nature. They are populated by stars with super-solar metallicity and
[/Fe]. Both objects have formed >80 % of their stellar mass within a
short (0.5 - 1.0 Gyrs) initial star formation episode occurred only ~1 Gyr
after the Big Bang. The third galaxy has a more extended star formation history
and a lower velocity dispersion. Thus we confirm two out of three candidates as
relics.Comment: 19 pages, 14 figures, accepted for publication in A&
INSPIRE: INvestigating Stellar Population In RElics II. First Data Release (DR1)
The INvestigating Stellar Population In RElics is an on-going project
targeting 52 ultra-compact massive galaxies at 0.1<z<0.5 with the X-Shooter@VLT
spectrograph (XSH). These objects are the perfect candidates to be 'relics',
massive red-nuggets formed at high-z (z>2) through a short and intense star
formation burst, that evolved passively and undisturbed until the present-day.
Relics provide a unique opportunity to study the mechanisms of star formation
at high-z. In this paper, we present the first INSPIRE Data Release, comprising
19 systems with observations completed in 2020. We use the methods already
presented in the INSPIRE Pilot, but revisiting the 1D spectral extraction. For
these 19 systems, we obtain an estimate of the stellar velocity dispersion,
fitting separately the two UVB and VIS XSH arms at their original resolution.
We estimate [Mg/Fe] abundances via line-index strength and mass-weighted
integrated stellar ages and metallicities with full spectral fitting on the
combined spectrum. Ages are generally old, in agreement with the photometric
ones, and metallicities are almost always super-solar, confirming the
mass-metallicity relation. The [Mg/Fe] ratio is also larger than solar for the
great majority of the galaxies, as expected. We find that 10 objects have
formed more than 75% of their stellar mass (M*) within 3 Gyr from the Big Bang
and classify them as relics. Among these, we identify 4 galaxies which had
already fully assembled their M* by that time. They are therefore `extreme
relics' of the ancient Universe. The INSPIRE DR1 catalogue of 10 known relics
to-date augment by a factor of 3.3 the total number of confirmed relics, also
enlarging the redshift window. It is therefore the largest publicly available
collection. Thanks to the larger number of systems, we can also better quantify
the existence of a 'degree of relicness', already hinted at the Pilot Paper.Comment: (Abstract abridged) 21 pages, 12 figures and 5 tables in the main
body, plus 3 figure and 1 table in the appendix, accepted for publication on
A&A. The associated data are available via the ESO Phase 3 Science Porta
KiDS ultracompact massive galaxies sp. obs.
Ultracompact massive galaxies (UCMGs), i.e., galaxies with stellar masses M*>8x1010M☉ and effective radii Re<1.5kpc, are very rare systems, in particular at low and intermediate redshifts. Their origin as well as their number density across cosmic time are still under scrutiny, especially because of the paucity of spectroscopically confirmed samples. We have started a systematic census of UCMG candidates within the ESO Kilo Degree Survey, together with a large spectroscopic follow-up campaign to build the largest possible sample of confirmed UCMGs. This is the third paper of the series and the second based on the spectroscopic follow-up program. Here, we present photometrical and structural parameters of 33 new candidates at redshifts 0.15≲z≲0.5 and confirm 19 of them as UCMGs, based on their nominal spectroscopically inferred M* and Re. This corresponds to a success rate of ∼58% , nicely consistent with our previous findings. The addition of these 19 newly confirmed objects allows us to fully assess the systematics on the system selection-and to finally reduce the number density uncertainties. Moreover, putting together the results from our current and past observational campaigns and some literature data, we build the largest sample of ucmgs ever collected, comprising 92 spectroscopically confirmed objects at 0.1≲z≲0.5. This number raises to 116, allowing for a 3σ tolerance on the M* and Re thresholds for the ucmg definition. For all these galaxies, we have estimated the velocity dispersion values at the effective radii, which have been used to derive a preliminary mass-velocity dispersion correlation
Discovery of two Einstein crosses from massive post--blue nugget galaxies at z>1 in KiDS
We report the discovery of two Einstein Crosses (ECs) in the footprint of the
Kilo-Degree Survey (KiDS): KIDS J232940-340922 and KIDS J122456+005048. Using
integral field spectroscopy from MUSE@VLT, we confirm their gravitational-lens
nature. In both cases, the four spectra of the source clearly show a prominence
of absorption features, hence revealing an evolved stellar population with
little star formation. The lensing model of the two systems, assuming a
singular isothermal ellipsoid (SIE) with external shear, shows that: 1) the two
crosses, located at redshift and 0.24, have Einstein radius kpc and 5.4 kpc, respectively; 2) their projected dark matter fractions
inside the half effective radius are 0.60 and 0.56 (Chabrier IMF); 3) the
sources are ultra-compact galaxies, kpc (at redshift ) and kpc (), respectively. These
results are unaffected by the underlying mass density assumption. Due to size,
blue color and absorption-dominated spectra, corroborated by low specific
star-formation rates derived from optical-NIR spectral energy distribution
fitting, we argue that the two lensed sources in these ECs are blue nuggets
migrating toward their quenching phase.Comment: Accepted for publication on APJ
The first sample of spectroscopically confirmed ultra-compact massive galaxies in the Kilo Degree Survey
We present results from an ongoing investigation using the Kilo Degree Survey
(KiDS) on the VLT Survey Telescope (VST) to provide a census of ultra-compact
massive galaxies (UCMGs), defined as galaxies with stellar masses and effective radii . UCMGs, which are expected to have undergone very few merger
events, provide a unique view on the accretion history of the most massive
galaxies in the Universe. Over an effective sky area of nearly 330 square
degrees, we select UCMG candidates from KiDS multi-colour images, which provide
high quality structural parameters, photometric redshifts and stellar masses.
Our sample of photometrically selected UCMGs at
represents the largest sample of UCMG candidates assembled to date over the
largest sky area. In this paper we present the first effort to obtain their
redshifts using different facilities, starting with first results for 28
candidates with redshifts , obtained at NTT and TNG telescopes. We
confirmed, as bona fide UCMGs, 19 out of the 28 candidates with new redshifts.
A further 46 UCMG candidates are confirmed with literature spectroscopic
redshifts (35 at ), bringing the final cumulative sample of
spectroscopically-confirmed lower-z UCMGs to 54 galaxies, which is the largest
sample at redshifts below . We use these spectroscopic redshifts to
quantify systematic errors in our photometric selection, and use these to
correct our UCMG number counts. We finally compare the results to independent
datasets and simulations.Comment: Accepted for publication on MNRAS, 27 pages, 13 figures, 7 tables.
This revised and improved version presents different updates. In particular,
systematics and uncertainties in the measurement of the effective radii are
now better discussed, and new plots are adde
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