Abstract
Gamma-ray bursts (GRBs) are classified into long and short events. Long GRBs (LGRBs) are associated with the end states of very massive stars, while short GRBs (SGRBs) are linked to the ...merger of compact objects. GRB 200826A was a peculiar event, because by definition it was an SGRB, with a rest-frame duration of ∼0.5 s. However, this event was energetic and soft, which is consistent with LGRBs. The relatively low redshift (
z
= 0.7486) motivated a comprehensive, multiwavelength follow-up campaign to characterize its host, search for a possible associated supernova (SN), and thus understand the origin of this burst. To this aim we obtained a combination of deep near-infrared (NIR) and optical imaging together with spectroscopy. Our analysis reveals an optical and NIR bump in the light curve whose luminosity and evolution are in agreement with several SNe associated to LGRBs. Analysis of the prompt GRB shows that this event follows the
E
p,i
–
E
iso
relation found for LGRBs. The host galaxy is a low-mass star-forming galaxy, typical of LGRBs, but with one of the highest star formation rates, especially with respect to its mass (
log
M
*
/
M
⊙
=
8.6
, SFR ∼ 4.0
M
⊙
yr
−1
). We conclude that GRB 200826A is a typical collapsar event in the low tail of the duration distribution of LGRBs. These findings support theoretical predictions that events produced by collapsars can be as short as 0.5 s in the host frame and further confirm that duration alone is not an efficient discriminator for the progenitor class of a GRB.
Exoplanet direct imaging with large ground based telescopes requires eXtreme Adaptive Optics that couples high-order adaptive optics and coronagraphy. A key element of such systems is the high-order ...wavefront sensor. We study here several high-order wavefront sensing approaches, and more precisely compare their sensitivity to noise. Three techniques are considered: the classical Shack-Hartmann sensor, the pyramid sensor and the recently proposed LIFTed Shack-Hartmann sensor. They are compared in a unified framework based on precise diffractive models and on the Fisher information matrix, which conveys the information present in the data whatever the estimation method. The diagonal elements of the inverse of the Fisher information matrix, which we use as a figure of merit, are similar to noise propagation coefficients. With these diagonal elements, so called "Fisher coefficients", we show that the LIFTed Shack-Hartmann and pyramid sensors outperform the classical Shack-Hartmann sensor. In photon noise regime, the LIFTed Shack-Hartmann and modulated pyramid sensors obtain a similar overall noise propagation. The LIFTed Shack-Hartmann sensor however provides attractive noise properties on high orders.
Context
. Massive stars play important roles throughout the universe; however, their formation remains poorly understood. Observations of jets and outflows in high-mass star-forming regions, as well ...as surveys of young stellar object (YSO) content, can help test theoretical models of massive star formation.
Aims
. We aim at characterizing the massive star-forming region AFGL 5180 in the near-infrared (NIR), identifying outflows and relating these to sub-mm/mm sources, as well as surveying the overall YSO surface number density to compare to massive star formation models.
Methods
. Broad- and narrow-band imaging of AFGL 5180 was made in the NIR with the Large Binocular Telescope, in both seeing-limited (~0.5″) and high angular resolution (~0.09″) Adaptive Optics (AO) modes, as well as with the
Hubble
Space Telescope. Archival continuum data from the Atacama Millimeter/Submillimeter Array (ALMA) was also utilized.
Results
. At least 40 jet knots were identified via NIR emission from H
2
and FeII tracing shocked gas. Bright jet knots outflowing from the central most massive protostar, S4 (estimated mass ~11
M
⊙
, via SED fitting), are detected towards the east of the source and are resolved in fine detail with the AO imaging. Additional knots are distributed throughout the field, likely indicating the presence of multiple driving sources. Sub-millimeter sources detected by ALMA are shown to be grouped in two main complexes, AFGL 5180 M and a small cluster ~15″ (0.15 pc in projection) to the south, AFGL 5180 S. From our NIR continuum images we identify YSO candidates down to masses of ~0.1
M
⊙
. Combined with the sub-mm sources, this yields a surface number density of such YSOs of
N
*
~ 10
3
pc
−2
within a projected radius of about 0.1 pc. Such a value is similar to those predicted by models of both core accretion from a turbulent clump environment and competitive accretion. The radial profile of
N
*
is relatively flat on scales out to 0.2 pc, with only modest enhancement around the massive protostar inside 0.05 pc, which provides additional constraints on these massive star formation models.
Conclusions
. This study demonstrates the utility of high-resolution NIR imaging, in particular with AO, for detecting outflow activity and YSOs in distant regions. The presented images reveal the complex morphology of outflow-shocked gas within the large-scale bipolar flow of a massive protostar, as well as clear evidence for several other outflow driving sources in the region. Finally, this work presents a novel approach to compare the observed YSO surface number density from our study against different models of massive star formation.
The
Gaia
Multipeak (GMP) technique can be used to identify large numbers of dual or lensed active galactic nucleus (AGN) candidates at subarcsec separation, allowing us to study both multiple ...supermassive black holes (SMBHs) in the same galaxy and rare, compact lensed systems. The observed samples can be used to test the predictions of the models of SMBH merging when (1) the selection function of the GMP technique is known, and (2) each system has been classified as a dual AGN, a lensed AGN, or an AGN/star alignment. Here we show that the GMP selection is very efficient for separations above 0.15″ when the secondary (fainter) object has a magnitude
G
≲ 20.5. We present the spectroscopic classification of five GMP candidates using VLT/ERIS and Keck/OSIRIS and compare them with the classifications obtained from (a) the near-IR colors of seven systems obtained with LBT/LUCI, and (b) the analysis of the total spatially unresolved spectra. We conclude that colors and integrated spectra can already provide reliable classifications of many systems. Finally, we summarize the confirmed dual AGNs at
z
> 0.5 selected by the GMP technique, and compare this sample with other such systems from the literature, concluding that GMP can provide a large number of confirmed dual AGNs at separations below 7 kpc.
ABSTRACT
We present a novel analysis of a young star cluster in the Large Magellanic cloud, R136-like, as seen by the Extremely Large Telescope (ELT). The main aim of this study is to quantify ...precision and accuracy of stellar proper motion measurements in crowded field when using an ELT working at its diffraction limit. This can serve as a reference study for future development of ELT scientific cases. In particular, we investigate our future ability to detect the dynamical signature of intermediate-mass black holes (IMBHs) with mass ∼104 M⊙ through detailed measurements of stellar proper motions. We have simulated two N-body dynamical cluster models with and without an IMBH. For each model, we have chosen two snapshots temporally spaced by 5 yr. Stellar fluxes in IJHK filters and star positions have been used to create ELT mock images for both single- and multiconjugate adaptive optics observing modes following the requierements given by ESO technical specifications for the first light imager. These images have been analysed using a classical software for seeing-limited data reduction, daophot/allstar. We make accurate photometry till the very faint pre-main-sequence stars, i.e. depending on the adaptive optics (AO) mode, magnitudes down to K ∼ 24 mag (single-conjugate AO) or K ∼ 22 mag (multiconjugate AO) in a total integration time of 20 min on target. Although daophot suite of programs is not devoted to precise astrometry, the astrometric accuracy is impressive, reaching few μas yr−1 or km s−1. In these assumptions, we are able to detect the IMBH signature at the centre of the cluster.
Laser Tomographic and Multi-Conjugate Adaptive Optics systems rely on natural guide stars to sense low order aberrations (tip/tilt and focus). LIFT is a novel focal plane wavefront sensor (WFS), ...performing a maximum likelihood phase retrieval on a single image, with better sensitivity than a 2 × 2 Hartmann-Shack WFS. Its performance for the estimation of tip/tilt and focus is similar to a pyramid WFS without modulation, but with a simpler set-up. We present here the LIFT concept and associated data processing, as well as experimental results. We validate the estimation of tip/tilt and focus, with monochromatic and large bandwidth light, and verify the low noise sensitivity predicted by theory.
Context.
Adaptive optics (AO) is a technique allowing for ground-based telescopes’ angular resolution to be improved drastically. The wavefront sensor (WFS) is one of the key components of such ...systems, driving the fundamental performance limitations.
Aims.
In this paper, we focus on a specific class of WFS: the Fourier-filtering wavefront sensors (FFWFSs). This class is known for its extremely high sensitivity. However, a clear and comprehensive noise propagation model for any kind of FFWFS is lacking.
Methods.
Considering read-out noise and photon noise, we derived a simple and comprehensive model allowing us to understand how these noises propagate in the phase reconstruction in the linear framework.
Results.
This new noise propagation model works for any kind of FFWFS, and it allows one to revisit the fundamental sensitivity limit of these sensors. Furthermore, a new comparison between widely used FFWFSs is held. We focus on the two main FFWFS classes used: the Zernike WFS (ZWFS) and the pyramid WFS (PWFS), bringing new understanding of their behavior.
The SOUL view of IRAS 20126+4104 Massi, F.; Caratti o Garatti, A.; Cesaroni, R. ...
Astronomy and astrophysics (Berlin),
4/2023, Volume:
672
Journal Article
Peer reviewed
Context.
We exploit the increased sensitivity of the recently installed adaptive optics SOUL at the LBT to obtain new high-spatial-resolution near-infrared images of the massive young stellar object ...IRAS20126+4104 and its outflow.
Aims.
We aim to derive the jet proper motions and kinematics, as well as to study its photometric variability by combining the novel performances of SOUL together with previous near-infrared images.
Methods.
We used both broad-band (
K
s
,
K
′) and narrow-band (Br
γ
, H2) observations from a number of near-infrared cameras (UKIRT/UFTI, SUBARU/CIAO, TNG/NICS, LBT/PISCES, and LBT/LUCI1) to derive maps of the continuum and the H
2
emission in the 2.12 µm line. Three sets of images, obtained with adaptive optics (AO) systems (CIAO, in 2003; FLAO, in 2012; SOUL, in 2020), allowed us to derive the proper motions of a large number of H
2
knots along the jet. Photometry from all images was used to study the jet variability.
Results.
We derived knot proper motions in the range of 1.7–20.3 mas yr
−1
(i.e. 13–158 km s
−1
at 1.64 kpc), implying an average outflow tangential velocity of ~80 km s
−1
. The derived knot dynamical age spans a ~200–4000 yr interval. A ring-like H
2
feature near the protostar location exhibits peculiar kinematics and may represent the outcome of a wide-angle wind impinging on the outflow cavity. Both H
2
geometry and velocities agree with those inferred from proper motions of the H
2
O masers, located at a smaller distance from the protostar. Although the total H
2
line emission from the knots does not exhibit time variations at a ⪞0.3 mag level, we have found a clear continuum flux variation (radiation scattered by the dust in the cavity opened by the jet) which is anti-correlated between the blue-shifted and red-shifted lobes and may be periodic (with a period of ~12–18 yr). We suggest that the continuum variability might be related to inner-disc oscillations which have also caused the jet precession.
Conclusions.
Our analysis shows that multi-epoch high-spatial-resolution imaging in the near-infrared is a powerful tool to unveil the physical properties of highly embedded massive protostars.
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