Dust dynamics in planet-driven spirals Sturm, J. A.; Rosotti, G. P.; Dominik, C.
Astronomy and astrophysics (Berlin),
11/2020, Letnik:
643
Journal Article
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Odprti dostop
Context.
Protoplanetary disks are known to host spiral features that are observed in scattered light, the ALMA continuum, and more recently in CO gas emission and gas dynamics. However, it is unknown ...whether spirals in gas and dust trace the same morphology.
Aims.
We aim to study the morphology and amplitude of dusty spirals as function of the Stokes number and the underlying mechanisms that cause a difference between dusty spirals and gas spirals. We then construct a model to relate the deviation from Keplerian rotation in the gas to a perturbation in surface density of the gas and dust.
Methods.
We used
FARGO-3D
with dust implementation to numerically study the spirals, after which the results were interpreted using a semi-analytical model. This model was tested on observational data to predict the perturbation of the spiral in gas dynamics based on the continuum data.
Results.
We find that the pitch angle of a spiral does not differ significantly between gas and dust. The amplitude of the dust spiral decreases with the Stokes number (St) and starts to fade out at a typical St > 0.1 as the dust becomes decoupled from the gas. The semi-analytical model provides an accurate and fast representation of the difference in the surface density of the spiral in dust and gas. We find a spiral in the TW Hya velocity residual map, never seen before, which is a feature in the vertical velocity and has a kink at the continuum gap, yielding strong evidence for a planet at 99 au.
Conclusions.
We built a model that gives an estimate of the underlying dynamics of dust in a spiral, which can serve as evidence of the planetary origin of spirals and can be a probe for the Stokes number in the disk.
In an effort to unify the nomenclature of Trypanosoma cruzi, the causative agent of Chagas disease, an updated system was agreed upon at the Second Satellite Meeting. A consensus was reached that T. ...cruzi strains should be referred to by six discrete typing units (T. cruzi I-VI). The goal of a unified nomenclature is to improve communication within the scientific community involved in T. cruzi research. The justification and implications will be presented in a subsequent detailed report.
GOALS: The Great Observatories All-Sky LIRG Survey Armus, L.; Mazzarella, J. M.; Evans, A. S. ...
Publications of the Astronomical Society of the Pacific,
06/2009, Letnik:
121, Številka:
880
Journal Article
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The Great Observatories All-Sky LIRG Survey (GOALS20) combines data from NASA’sSpitzer Space Telescope,
Chandra X-Ray Observatory,
Hubble Space Telescope(HST), andGalaxy Evolution Explorer(GALEX) ...observatories, together with ground-based data, into a comprehensive imaging and spectroscopic survey of over 200 low-redshift (
z < 0.088
z
<
0.088
), Luminous Infrared Galaxies (LIRGs). The LIRGs are a complete subset of theIRASRevised Bright Galaxy Sample (RBGS), which comprises 629 extragalactic objects with 60 μm flux densities above 5.24 Jy, and Galactic latitudes above five degrees. The LIRGs targeted in GOALS span the full range of nuclear spectral types defined via traditional optical line-ratio diagrams (type-1 and type-2 AGN, LINERs, and starbursts) as well as interaction stages (major mergers, minor mergers, and isolated galaxies). They provide an unbiased picture of the processes responsible for enhanced infrared emission in galaxies in the local Universe. As an example of the analytic power of the multiwavelength GOALS data set, we presentSpitzer, Chandra, HST,andGALEXimages and spectra for the interacting system VV 340 (IRAS
F14547 + 2449
F
14547
+
2449
). TheSpitzerMIPS imaging data indicates that between 80–95% of the total far-infrared emission (or about5 × 1011 L
⊙
5
×
10
11
L
⊙
) originates in VV 340 north. While theSpitzerIRAC colors of VV 340 north and south are consistent with star-forming galaxies, both theSpitzerIRS andChandraACIS data indicate the presence of an AGN in VV 340 north. The observed line fluxes, without correction for extinction, imply that the AGN accounts for less than 10%–20% of the observed infrared emission. The X-ray data are consistent with a heavily absorbed (
N
H
≥1024 cm-2
N
H
≥
10
24
cm
-
2
) AGN. The GALEX far and near-UV fluxes imply a extremely large infrared “excess” (IRX) for the system (FIR/Ffuv ∼ 81
F
IR
/
F
fuv
∼
81
) which is well above the correlation seen in starburst galaxies. Most of this excess is driven by VV 340 N, which has an IR excess of nearly 400. The VV 340 system seems to be comprised of two very different galaxies: an infrared luminous edge-on galaxy (VV 340 north) that dominates the long-wavelength emission from the system, which hosts a buried AGN; and a face-on starburst (VV 340 south) that dominates the short-wavelength emission.
Abstract We present JWST MIRI MRS observations of the edge-on protoplanetary disk around the young subsolar-mass star Tau 042021, acquired as part of the Cycle 1 GO program “Mapping Inclined Disk ...Astrochemical Signatures.” These data resolve the mid-IR spatial distributions of H 2 , revealing X-shaped emission extending to ∼200 au above the disk midplane with a semiopening angle of 35° ± 5°. We do not velocity-resolve the gas in the spectral images, but the measured semiopening angle of the H 2 is consistent with a magnetohydrodynamic wind origin. A collimated, bipolar jet is seen in forbidden emission lines from Ne ii , Ne iii , Ni ii , Fe ii , Ar ii , and S iii . Extended H 2 O and CO emission lines are also detected, reaching diameters of ∼90 and 190 au, respectively. Hot molecular emission is not expected at such radii, and we interpret its extended spatial distribution as scattering of inner disk molecular emission by dust grains in the outer disk surface. H i recombination lines, characteristic of inner disk accretion shocks, are similarly extended and are likely also scattered light from the innermost star–disk interface. Finally, we detect extended polycyclic aromatic hydrocarbon (PAH) emission at 11.3 μ m cospatial with the scattered-light continuum, making this the first low-mass T Tauri star around which extended PAHs have been confirmed, to our knowledge. MIRI MRS line images of edge-on disks provide an unprecedented window into the outflow, accretion, and scattering processes within protoplanetary disks, allowing us to constrain the disk lifetimes and accretion and mass-loss mechanisms.
We report the results from a systematic search for molecular (OH 119 micron) outflows with Herschel/PACS in a sample of 43 nearby (z < 0.3) galaxy mergers, mostly ultraluminous infrared galaxies ...(ULIRGs) and QSOs. We find that the character of the OH feature (strength of the absorption relative to the emission) correlates with that of the 9.7 micron silicate feature, a measure of obscuration in ULIRGs. Unambiguous evidence for molecular outflows, based on the detection of OH absorption profiles with median velocities more blueshifted than−50 km/s, is seen in 26 (70%) of the 37 OH-detected targets, suggesting a wide-angle (approx. 145 deg.) outflow geometry. Conversely, unambiguous evidence for molecular inflows, based on the detection of OH absorption profiles with median velocities more redshifted than +50 km/s is seen in only four objects, suggesting a planar or filamentary geometry for the inflowing gas. Terminal outflow velocities of approx. −1000 km/s are measured in several objects, but median outflow velocities are typically approx.−200 km/s−1. While the outflow velocities show no statistically significant dependence on the star formation rate, they are distinctly more blueshifted among systems with large active galactic nucleus (AGN) fractions and luminosities log (L(sub AGN)/L(sub solar)) => 11.8 +/- 0.3. The quasars in these systems play a dominant role in driving the molecular outflows. However, the most AGN dominated systems, where OH is seen purely in emission, show relatively modest OH line widths, despite their large AGN luminosities, perhaps indicating that molecular outflows subside once the quasar has cleared a path through the obscuring material.
Selective digestive tract decontamination (SDD) and selective oropharyngeal decontamination (SOD) eradicate gram-negative bacteria (GNB) from the intestinal and respiratory tract in intensive care ...unit (ICU) patients, but their effect on antibiotic resistance remains controversial.
We quantified the effects of SDD and SOD on bacterial ecology in 13 ICUs that participated in a study, in which SDD, SOD, or standard care was used during consecutive periods of 6 months (de Smet AM, Kluytmans JA, Cooper BS, Mascini EM, Benus RF, van der Werf TS, van der Hoeven JG, Pickkers P, Bogaers-Hofman D, van der Meer NJ, et al. N Engl J Med 2009;360:20-31).
Point prevalence surveys of rectal and respiratory samples were performed once monthly in all ICU patients (receiving or not receiving SOD/SDD). Effects of SDD on rectal, and of SDD/SOD on respiratory tract, carriage of GNB were determined by comparing results from consecutive point prevalence surveys during intervention (6 mo for SDD and 12 mo for SDD/SOD) with consecutive point prevalence data in the pre- and postintervention periods.
During SDD, average proportions of patients with intestinal colonization with GNB resistant to either ceftazidime, tobramycin, or ciprofloxacin were 5, 7, and 7%, and increased to 15, 13, and 13% postintervention (P < 0.05). During SDD/SOD resistance levels in the respiratory tract were not more than 6% for all three antibiotics but increased gradually (for ceftazidime; P < 0.05 for trend) during intervention and to levels of 10% or more for all three antibiotics postintervention (P < 0.05).
SOD and SDD have marked effects on the bacterial ecology in an ICU, with rising ceftazidime resistance prevalence rates in the respiratory tract during intervention and a considerable rebound effect of ceftazidime resistance in the intestinal tract after discontinuation of SDD.
The purpose of this study was to determine the overall trend of computed tomography (CT) utilization in the pediatric emergency department (PED) from 2003 to 2010 and to determine trends categorized ...by common chief complaints.
Electronic chart records at 2 tertiary care PEDs within a large pediatric health care system were reviewed from January 2003 through December 2010. The annual CT utilization rate, by anatomic location, was determined. Annual CT utilization rates were compared with alternative imaging trends for visits with chief complaints of head injury, seizure, and abdominal pain. Analysis was performed with linear regression.
There was no change in overall CT utilization from 2003 to 2010 (β 0.25, 95% confidence interval CI -1.61 to 2.73) or within anatomic subgroups. Head CT utilization for the chief complaints of seizure (β -0.97, 95% CI -1.44 to -0.90) and head injury (β -0.93, 95% CI -1.71 to -0.73) showed significant declines. Although there was no change in the abdominal CT utilization rate for abdominal pain, abdominal ultrasound utilization for abdominal pain significantly increased (β 0.89, 95% CI 0.25-0.79).
Our data showed no overall increase in CT utilization through 2010. In areas where alternative non-radiation-based modalities were options, there were decreased CT trends and increased use of potential alternative non-radiation-based modalities. This is the first large PED cohort study to show a decrease in CT utilization in recent years in a regional pediatric referral center and may correlate with increased awareness of radiation risk in children.
ABSTRACT
We report the results from a comprehensive study of 74 ultraluminous infrared
galaxies (ULIRGs) and 34 Palomar-Green (PG) quasars within
z
∼
0.3 observed with the
Spitzer
Infrared ...Spectrograph (IRS). The
contribution of nuclear activity to the bolometric luminosity in these systems
is quantified using six independent methods that span a range in wavelength and
give consistent results within ∼±10%–15% on average. This agreement suggests
that deeply buried active galactic nuclei (AGNs) invisible to
Spitzer
IRS but bright in the far-infrared are not common
in this sample. The average derived AGN contribution in ULIRGs is ∼35%–40%,
ranging from ∼15%–35% among “cool”
(
f
25
/
f
60
⩽ 0.2)
optically classified H
ii
-like and LINER ULIRGs to ∼50 and ∼75% among
warm Seyfert 2 and Seyfert 1 ULIRGs, respectively. This number exceeds ∼80% in
PG QSOs. ULIRGs fall in one of three distinct AGN classes: (1) objects with
small extinctions and large polycyclic aromatic hydrocarbon (PAH) equivalent
widths are highly starburst-dominated; (2) systems with large extinctions and
modest PAH equivalent widths have larger AGN contributions, but still tend to be
starburst-dominated; and (3) ULIRGs with both small extinctions and small PAH
equivalent widths host AGN that are at least as powerful as the starbursts. The
AGN contributions in class 2 ULIRGs are more uncertain than in the other
objects, and we cannot formally rule out the possibility that these objects
represent a physically distinct type of ULIRGs. A morphological trend is seen
along the sequence (1)–(2)–(3), in general agreement with the standard ULIRG−QSO
evolution scenario and suggestive of a broad peak in extinction during the
intermediate stages of merger evolution. However, the scatter in this sequence,
including the presence of a significant number of AGN-dominated systems prior to
coalescence and starburst-dominated but fully merged systems, implies that black
hole accretion, in addition to depending on the merger phase, also has a strong
chaotic/random component, as in local AGNs.
Abstract
We report the first detection of variability in the mid-infrared neon line emission of a protoplanetary disk by comparing a JWST Mid-InfraRed Instrument Medium Resolution Spectrometer ...spectrum of SZ Cha taken in 2023 with a Spitzer Infrared Spectrograph Short-High spectrum of this object from 2008. We measure the Ne
iii
-to-Ne
ii
line flux ratio, which is a diagnostic of the high-energy radiation field, to distinguish between the dominance of EUV- or X-ray-driven disk photoevaporation. We find that the Ne
iii
-to-Ne
ii
line flux ratio changes significantly from ∼1.4 in 2008 to ∼0.2 in 2023. This points to a switch from EUV-dominated to X-ray-dominated photoevaporation of the disk. We present contemporaneous ground-based optical spectra of the H
α
emission line that show the presence of a strong wind in 2023. We propose that this strong wind prevents EUV radiation from reaching the disk surface while the X-rays permeate the wind and irradiate the disk. We speculate that at the time of the Spitzer observations, the wind was suppressed and EUV radiation reached the disk. These observations confirm that the MIR neon emission lines are sensitive to changes in high-energy radiation reaching the disk surface. This highlights the Ne
iii
-to-Ne
ii
line flux ratio as a tool to gauge the efficiency of disk photoevaporation in order to provide constraints on the planet formation timescale. However, multiwavelength observations are crucial to interpret the observations and properly consider the star–disk connection.
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