ABSTRACT
Recent advances in the stellar population studies of unresolved galaxies in the NIR domain demonstrated that it contains several line-strength indices to be potentially used as diagnostics ...for stellar population properties. Reduction of the extinction and possibility to disentangle different stellar populations dominating different spectral ranges are obviously beneficial. To this aim, we have investigated the connections between 19 Lick/IDS indices and 39 NIR indices measured in the central regions of 32 galaxies observed with X-shooter. We adopted a systematic approach to deriving a correlation matrix using all the optical and NIR indices measured for the galaxies and building new NIR composite indices to maximize their correlations with the best age and metallicity optical tracers. We found that the new T1 and AlFeCr composite indices are promising age and metallicity diagnostics in NIR, respectively. We finally tested the T1 and AlFeCr indices with the predictions of simple stellar populations models, and we found that the models show a general agreement with the data. Some fine tuning and further comparison between models and data, which are now largely available, is necessary to reach the prediction level of the optical line-strength indices.
ABSTRACT
We present surface photometry and stellar kinematics of IC 3167, a dwarf galaxy hosting a lopsided weak bar and infalling into the Virgo cluster. We measured the bar radius and strength from ...broad-band imaging and bar pattern speed by applying the Tremaine–Weinberg method to stellar-absorption integral-field spectroscopy. We derived the ratio of the corotation radius to bar radius (${\cal {R}}=1.7^{+0.5}_{-0.3}$) from stellar kinematics and bar pattern speed. The probability that the bar is rotating slowly is more than twice as likely as that the bar is fast. This allows us to infer that the formation of this bar was triggered by the ongoing interaction rather than the internal processes.
ABSTRACT
We measured the equivalent width of a large set of near-infrared (NIR, 0.8–2.4$\ \mu$m) line-strength indices in XShooter medium-resolution spectra of the central regions of 14 galaxies. We ...found that two aluminum indices, Al at 1.31 μm and Al1 at 1.67 μm, and two CO indices, CO1 at 1.56 μm and CO4 at 1.64 μm, are tightly correlated with the velocity dispersion. Moreover, the NIR Al and CO1 indices show strong correlations with the optical Mg2 and Mgb indices, which are usually adopted as α/Fe-enhancement diagnostics. The molecular FeH1 index at 1.58 μm correlates tightly with the optical 〈Fe〉 and MgFe′ indices, which are used as total metallicity diagnostics. The NIR Paβ index at 1.28 μm has a behaviour similar to the optical Hβ index, which is a diagnostic of mean age. We defined two new composite indices, 〈Al〉 and AlFeH, as possible candidates to be used as NIR diagnostics of total metallicity and α/Fe enhancement. The NIR 〈Al〉 index has a strong correlation with the optical Mg2 and Mgb indices, while the AlFeH index is tightly correlated with the optical 〈Fe〉 and MgFe′ indices. The distribution of the data points in the NIR Paβ–〈Al〉 and Paβ–AlFeH diagrams mimics that in the optical MgFe′–Hβ and Mgb–〈Fe〉 diagrams, which are widely used to constrain the properties of the unresolved stellar populations. We concluded that some NIR line-strength indices could be useful in studying stellar populations as well as in fine-tuning stellar population models.
We report the detection of transits by the $3.1~M_{\rm Jup}$ companion to the $V=8.17$ G0V star HD 17156. The transit was observed by three independant observers on Sep. 9/10, 2007 (two in central ...Italy and one in the Canary Islands), who obtained detections at confidence levels of 3.0σ, 5.3σ, and 7.9σ, respectively. The observations were carried out under the auspices of the Transitsearch.org network, which organizes follow-up photometric transit searches of known planet-bearing stars during the time intervals when transits might be expected to occur. Analyses of the 7.9σ data set indicates a transit depth $d=0.0062$ ± 0.0004 and a transit duration $t=186$ ± 5 min. These values are consistent with the transit of a Jupiter-sized planet with an impact parameter $b=a \cos{i}/R_{\star} \sim 0.8$. This planet occupies a unique regime among known transiting extrasolar planets, both as a result of its large orbital eccentricity ($e=0.67$) and long orbital period ($P=21.2~{\rm d}$). The planet receives a 26-fold variation in insolation during the course of its orbit, which will make it a useful object for characterizing exoplanetary atmospheric dynamics.
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Context.
Stellar population studies in the infrared (IR) wavelength range have two main advantages with respect to the optical regime: they probe different populations, because most of the light in ...the IR comes from redder and generally older stars, and they allow us to see through dust because IR light is less affected by extinction. Unfortunately, IR modeling work was halted by the lack of adequate stellar libraries, but this has changed in the recent years.
Aims.
Our project investigates the sensitivity of various spectral features in the 1−5
μ
m wavelength range to the physical properties of stars (
T
eff
, Fe/H, log
g
) and aims to objectively define spectral indices that can characterize the age and metallicity of unresolved stellar populations.
Methods.
We implemented a method that uses derivatives of the indices as functions of
T
eff
, Fe/H or log
g
across the entire available wavelength range to reveal the most sensitive indices to these parameters and the ranges in which these indices work.
Results.
Here, we complement the previous work in the
I
and
K
bands, reporting a new system of 14, 12, 22, and 12 indices for Y, J, H, and L atmospheric windows, respectively, and describe their behavior. We list the equivalent widths of these indices for the Infrared Telescope Facility (IRTF) spectral library stars.
Conclusions.
Our analysis indicates that features sensitive to the effective temperature are present and measurable in all the investigated atmospheric windows at the spectral resolution and in the metallicity range of the IRTF library for a signal-to-noise ratio greater than 20−30. The surface gravity is more challenging and only indices in the H and J windows are best suited for this. The metallicity range of the stars with available spectra is too narrow to search for suitable diagnostics. For the spectra of unresolved galaxies, the defined indices are valuable tools in tracing the properties of the stars in the IR-dominant stellar populations.
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Context. Stellar population studies in the infrared (IR) wavelength range have two main advantages with respect to the optical regime: they probe different populations, because most of the light in ...the IR comes from redder and generally older stars, and they allow us to see through dust because IR light is less affected by extinction. Unfortunately, IR modeling work was halted by the lack of adequate stellar libraries, but this has changed in the recent years. Aims. Our project investigates the sensitivity of various spectral features in the 1−5 μm wavelength range to the physical properties of stars (Teff, Fe/H, log g) and aims to objectively define spectral indices that can characterize the age and metallicity of unresolved stellar populations. Methods. We implemented a method that uses derivatives of the indices as functions of Teff, Fe/H or log g across the entire available wavelength range to reveal the most sensitive indices to these parameters and the ranges in which these indices work. Results. Here, we complement the previous work in the I and K bands, reporting a new system of 14, 12, 22, and 12 indices for Y, J, H, and L atmospheric windows, respectively, and describe their behavior. We list the equivalent widths of these indices for the Infrared Telescope Facility (IRTF) spectral library stars. Conclusions. Our analysis indicates that features sensitive to the effective temperature are present and measurable in all the investigated atmospheric windows at the spectral resolution and in the metallicity range of the IRTF library for a signal-to-noise ratio greater than 20−30. The surface gravity is more challenging and only indices in the H and J windows are best suited for this. The metallicity range of the stars with available spectra is too narrow to search for suitable diagnostics. For the spectra of unresolved galaxies, the defined indices are valuable tools in tracing the properties of the stars in the IR-dominant stellar populations.
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New binaries from the SHINE survey Bonavita, M.; Gratton, R.; Desidera, S. ...
Astronomy & astrophysics,
07/2022, Volume:
663
Journal Article, Web Resource
Peer reviewed
Open access
We present the multiple stellar systems observed within the SpHere INfrared survey for Exoplanet (SHINE). SHINE searched for sub-stellar companions to young stars using high contrast imaging. ...Although stars with known stellar companions within the SPHERE field of view (< 5.5 arcsec) were removed from the original target list, we detected additional stellar companions to 78 of the 463 SHINE targets observed so far. Twenty-seven per cent of the systems have three or more components. Given the heterogeneity of the sample in terms of observing conditions and strategy, tailored routines were used for data reduction and analysis, some of which were specifically designed for these datasets. We then combined SPHERE data with literature and archival data, TESS light curves, and
Gaia
parallaxes and proper motions for an accurate characterisation of the systems. Combining all data, we were able to constrain the orbits of 25 systems. We carefully assessed the completeness of our sample for separations between 50–500 mas (corresponding to periods of a few years to a few decades), taking into account the initial selection biases and recovering part of the systems excluded from the original list due to their multiplicity. This allowed us to compare the binary frequency for our sample with previous studies and highlight interesting trends in the mass ratio and period distribution. We also found that, when such an estimate was possible, the values of the masses derived from dynamical arguments were in good agreement with the model predictions. Stellar and orbital spins appear fairly well aligned for the 12 stars that have enough data, which favours a disk fragmentation origin. Our results highlight the importance of combining different techniques when tackling complex problems such as the formation of binaries and show how large samples can be useful for more than one purpose.
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Aims
. R Coronae Australis (R CrA) is the brightest star of the Coronet nebula of the Corona Australis (CrA) star forming region. This star is very red in color, probably due to dust absorption, and ...is strongly variable. High-contrast instruments allow for an unprecedented direct exploration of the immediate circumstellar environment of this star.
Methods
. We observed R CrA with the near-infrared (NIR) channels (IFS and IRDIS) of SPHERE at the Very Large Telescope (VLT). In this paper, we used four different epochs, three of which are from open time observations while one is from SPHERE guaranteed time. The data were reduced using the data reduction and handling pipeline and the SPHERE Data Center. We implemented custom IDL routines on the reduced data with the aim to subtract the speckle halo. We have also obtained pupil-tracking
H
-band (1.45−1.85
μ
m) observations with the VLT/SINFONI NIR medium-resolution (
R
∼ 3000) spectrograph.
Results
. A companion was found at a separation of 0.156″ from the star in the first epoch and increasing to 0.184″ in the final epoch. Furthermore, several extended structures were found around the star, the most noteworthy of which is a very bright jet-like structure northeast from the star. The astrometric measurements of the companion in the four epochs confirm that it is gravitationally bound to the star. The SPHERE photometry and SINFONI spectrum, once corrected for extinction, point toward a spectral type object that is early
M
with a mass between 0.3 and 0.55
M
⊙
. The astrometric analyis provides constraints on the orbit paramenters:
e
∼ 0.4, semimajor axis at 27–28 au, inclination of ∼70°, and a period larger than 30 yr. We were also able to put constraints of few
M
Jup
on the mass of possible other companions down to separations of few tens of au.
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Aims. R Coronae Australis (R CrA) is the brightest star of the Coronet nebula of the Corona Australis (CrA) star forming region. This star is very red in color, probably due to dust absorption, and ...is strongly variable. High-contrast instruments allow for an unprecedented direct exploration of the immediate circumstellar environment of this star. Methods. We observed R CrA with the near-infrared (NIR) channels (IFS and IRDIS) of SPHERE at the Very Large Telescope (VLT). In this paper, we used four different epochs, three of which are from open time observations while one is from SPHERE guaranteed time. The data were reduced using the data reduction and handling pipeline and the SPHERE Data Center. We implemented custom IDL routines on the reduced data with the aim to subtract the speckle halo. We have also obtained pupil-tracking H-band (1.45−1.85 μm) observations with the VLT/SINFONI NIR medium-resolution (R ∼ 3000) spectrograph. Results. A companion was found at a separation of 0.156″ from the star in the first epoch and increasing to 0.184″ in the final epoch. Furthermore, several extended structures were found around the star, the most noteworthy of which is a very bright jet-like structure northeast from the star. The astrometric measurements of the companion in the four epochs confirm that it is gravitationally bound to the star. The SPHERE photometry and SINFONI spectrum, once corrected for extinction, point toward a spectral type object that is early M with a mass between 0.3 and 0.55 M⊙. The astrometric analyis provides constraints on the orbit paramenters: e ∼ 0.4, semimajor axis at 27–28 au, inclination of ∼70°, and a period larger than 30 yr. We were also able to put constraints of few MJup on the mass of possible other companions down to separations of few tens of au.
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Background Robotic lobectomy with radical lymph node dissection is a new frontier of minimally invasive thoracic surgery. Series of sublobar anatomic resection for primary initial lung cancers or for ...metastasis using video-assisted thoracic surgery have been reported but no cases have been so far reported using the robot-assisted approach. We present the technique and surgical outcome of our initial experience. Methods Clinical data of patients undergoing robotic lung anatomic segmentectomy were retrospectively reviewed. All cases were done using the DaVinci System. A 3- or 4-incision strategy with a 3-cm utility incision in the anterior fourth or fifth intercostal space was performed. Individual ligation and division of the hilar structures was performed using Hem-o-Lok (Teleflex Medical, Research Triangle Park, NC) or endoscopic staplers. The parenchyma was transected with endovascular staplers introduced by the bedside assistant mainly through the utility incision. Systematic mediastinal lymph node dissection or sampling was performed. Results From 2008 to 2010, 17 patients underwent a robot-assisted lung anatomic segmentectomy in two centers. There were 10 women and 7 men with a mean age of 68.2 years (range, 32 to 82). Mean duration of surgery was 189 minutes. There were no major intraoperative complications. Conversion to open procedure was never required. Postoperative morbidity rate was 17.6% with pneumonia in 1 case and prolonged air leaks in 2 patients. Median postoperative stay was 5 days (range, 2 to 14), and postoperative mortality was 0%. Final pathology was non-small cell lung cancer in 8 patient, typical carcinoids in 2, and lung metastases in 7. Conclusions Robotic anatomic lung segmentectomy is feasible and safe procedure. Robotic system, by improving ergonomic, surgeon view and precise movements, may make minimally invasive segmentectomy easier to adopt and perform.
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