77 research outputs found
EIFIS: a modular extreme integral field spectrograph for the 10.4m GTC
EIFIS (Extreme Integral FIeld Spectrograph) is a modular integral field
spectrograph, based on image slicers, and makes use of new, large format
detectors. The concept is thought to cover the largest possible field of view
while producing spectroscopy over the complete optical range (3 000 - 10 000
\r{A}) at a medium resolving power of about 2400. In the optimal concept, each
module covers a field of view of 38" x 38" with 0.3" spaxels, which is fed into
a double spectrograph with common collimator optics. The blue arm covers the
spectral range between 3000 and 5600 \r{A} and the red arm between 5400 and
10100 \r{A}, allowing for an overlap range. The spectra are imaged onto 9.2k x
9.2k detectors using a double pseudoslit. The proposed design for the 10.4m
Gran Telescopio Canarias uses a total of 6 such modules to cover a total of
2.43 square arcminutes. Here we will present the conceptual design of the
instrument and a feasibility study of the optical and mechanical design of the
spectrographs. We discuss the limitations and alternative designs and its
potential to produce leading edge science in the era of extremely large
telescopes and the James Webb Space Telescope.Comment: Submitted to the Proceedings of the SPIE, Astronomical Telescopes and
Instrumentatio
NGC 2770: high supernova rate due to interaction
Galaxies which hosted many core-collapse supernovae (SN) explosions can be
used to study the conditions necessary for the formation of massive stars. NGC
2770 was dubbed a SN factory, because it hosted four core-collapse SNe in 20
years (three type Ib and one type IIn). Its star formation rate (SFR) was
reported not to be enhanced and therefore not compatible with such a high SN
rate. We aim at explaining the high SN rate of NGC 2770. We used archival HI
line data for NGC 2770 and reinterpret the Halpha and optical continuum data.
Even though the continuum-based SFR indicators do not yield high values, the
dust-corrected Halpha luminosity implies a high SFR, consistent with the high
SN rate. Such disparity between the SFR estimators is an indication of recently
enhanced star formation activity, because the continuum indicators trace long
timescale of the order of 100 Myr, unlike the line indicators, which trace
timescales of the order of 10 Myr. Hence, the unique feature of NGC 2770
compared to other galaxies is the fact that it is observed very recently after
the enhancement of the SFR. It also has high dust extinction, E(B-V) above 1
mag. We provide support for the hypothesis that the increased SFR in NGC 2770
is due to the interaction with its companion galaxies. We report an HI bridge
between NGC 2770 and its closest companion and the existence of a total of four
companions within 100 kpc (one identified for the first time). There are no
clear HI concentrations close to the positions of SNe in NGC 2770 such as those
detected for hosts of gamma-ray bursts (GRBs) and broad-lined SNe type Ic
(IcBL). This suggests that the progenitors of type Ib SNe are not born out of
recently accreted atomic gas, as was suggested for GRB and IcBL SN progenitors.Comment: Astronomy & Astrophysics, in press, 8 pages, 3 figures, 1 tabl
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The Population of Helium-Merger Progenitors: Observational Predictions
The helium-merger gamma-ray burst progenitor is produced by the rapid accretion onto a compact remnant (neutron star or black hole) when it undergoes a common envelope inspiral with its companion’s helium core. This merger phase produces a very distinct environment around these outbursts and recent observations suggest that, in some cases, we are detecting the signatures of the past merger in the GRB afterglow. These observations allow us, for the first time, to study the specific features of the helium merger progenitor. In this paper, we couple population synthesis calculations to our current understanding of gamma-ray burst engines and common envelope evolution to make observational predictions for the helium-merger gamma-ray burst population. Many mergers do not produce GRB outbursts and we discuss the implications of these mergers with the broader population of astrophysical transients.Astronom
NGC 2770 - a supernova Ib factory?
NGC 2770 has been the host of three supernovae of Type Ib during the last 10
years, SN 1999eh, SN 2007uy and SN 2008D. SN 2008D attracted special attention
due to the serendipitous discovery of an associated X-ray transient. In this
paper, we study the properties of NGC 2770 and specifically the three SN sites
to investigate whether this galaxy is in any way peculiar to cause a high
frequency of SNe Ib. We model the global SED of the galaxy from broadband data
and derive a star-formation and SN rate comparable to the values of the Milky
Way. We further study the galaxy using longslit spectroscopy covering the major
axis and the three SN sites. From the spectroscopic study we find subsolar
metallicities for the SN sites, a high extinction and a moderate star-formation
rate. In a high resolution spectrum, we also detect diffuse interstellar bands
in the line-of-sight towards SN 2008. A comparison of NGC 2770 to the global
properties of a galaxy sample with high SN occurance (at least 3 SN in the last
100 years) suggests that NGC 2770 is not particularly destined to produce such
an enhancement of observed SNe observed. Its properties are also very different
from gamma-ray burst host galaxies. Statistical considerations on SN Ib
detection rates give a probability of ~1.5% to find a galaxy with three Ib SNe
detected in 10 years. The high number of rare Ib SNe in this galaxy is
therefore likely to be a coincidence rather than special properties of the
galaxy itself. NGC 2770 has a small irregular companion, NGC 2770B, which is
highly starforming, has a very low mass and one of the lowest metallicities
detected in the nearby universe as derived from longslit spectroscopy. In the
most metal poor part, we even detect Wolf-Rayet features, against the current
models of WR stars which require high metallicities.Comment: 15 pages, 10 figures, submitted to Ap
Toward a Dimensional Assessment of Externalizing Disorders in Children: Reliability and Validity of a Semi-Structured Parent Interview
Objective
This study assesses the reliability and validity of the DSM-5-based, semi-structured Clinical Parent Interview for Externalizing Disorders in Children and Adolescents (ILF-EXTERNAL).
Method
Participant data were drawn from the ongoing ESCAschool intervention study. The ILF-EXTERNAL was evaluated in a clinical sample of 474 children and adolescents (aged 6-12 years, 92 females) with symptoms of attention-deficit/hyperactivity disorder (ADHD). To obtain interrater reliability, the one-way random-effects, absolute agreement models of the intraclass correlation (ICC) for single ICC(1,1) and average measurements ICC(1,3) were computed between the interviewers and two independent raters for 45 randomly selected interviews involving ten interviewers. Overall agreement on DSM-5 diagnoses was assessed using Fleiss' kappa. Further analyses evaluated internal consistencies, item-total correlations as well as correlations between symptom severity and the degree of functional impairment. Additionally, parents completed the German version of the Child Behavior Checklist (CBCL) and two DSM-5-based parent questionnaires for the assessment of ADHD symptoms and symptoms of disruptive behavior disorders (FBB-ADHS; FBB-SSV), which were used to evaluate convergent and divergent validity.
Results
ICC coefficients demonstrated very good to excellent interrater reliability on the item and scale level of the ILF-EXTERNAL [scale level: ICC(1,1) = 0.83-0.95; ICC(1,3) = 0.94-0.98]. Overall kappa agreement on DSM-5 diagnoses was substantial to almost perfect for most disorders (0.38 ≤ κ ≤ 0.94). With some exceptions, internal consistencies (0.60 ≤ α ≤ 0.86) and item-total correlations (0.21 ≤ r ≤ 0.71) were generally satisfactory to good. Furthermore, higher symptom severity was associated with a higher degree of functional impairment. The evaluation of convergent validity revealed positive results regarding clinical judgment and parent ratings (FBB-ADHS; FBB-SSV). Correlations between the ILF-EXTERNAL scales and the CBCL Externalizing Problems were moderate to high. Finally, the ILF-EXTERNAL scales were significantly more strongly associated with the CBCL Externalizing Problems than with the Internalizing Problems, indicating divergent validity.
Conclusion
In clinically referred, school-age children, the ILF-EXTERNAL demonstrates sound psychometric properties. The ILF-EXTERNAL is a promising clinical interview and contributes to high-quality diagnostics of externalizing disorders in children and adolescents
The Exotic Type Ic Broad-lined Supernova SN 2018gep: Blurring the Line between Supernovae and Fast Optical Transients
A revised host galaxy association for GRBÂ 020819B: a high-redshift dusty starburst, not a low-redshift gas-poor spiral
The purported spiral host galaxy of GRB 020819B at z = 0.41 has been seminal in establishing our view of the diversity of long-duration gamma-ray burst environments: Optical spectroscopy of this host provided evidence that gamma-ray bursts (GRBs) can form even at high metallicities, whereas millimetric observations suggested that GRBs may preferentially form in regions with minimal molecular gas. We report new observations from the Very Large Telescope (Multi Unit Spectroscopic Explorer and X-shooter), which demonstrate that the purported host is an unrelated foreground galaxy. The probable radio afterglow is coincident with a compact, highly star forming, dusty galaxy at z = 1.9621. The revised redshift naturally explains the apparent non-detection of CO (3–2) line emission at the afterglow site from the Atacama Large Millimetre Observatory. There is no evidence that molecular gas properties in GRB host galaxies are unusual, and limited evidence that GRBs can form readily at a super-Solar metallicity
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