129 research outputs found
A Large-field J=1-0 Survey of CO and Its Isotopologues Toward the Cassiopeia A Supernova Remnant
We have conducted a large-field simultaneous survey of CO, CO,
and CO emission toward the Cassiopeia A (Cas A) supernova
remnant (SNR), which covers a sky area of . The
Cas giant molecular cloud (GMC) mainly consists of three individual clouds with
masses on the order of . The total mass derived from the
emission of the GMC is 2.1 and is
9.5 from the emission. Two regions with
broadened (67 km s) or asymmetric CO line profiles are found
in the vicinity (within a 10 region) of the Cas A SNR, indicating
possible interactions between the SNR and the GMC. Using the GAUSSCLUMPS
algorithm, 547 CO clumps are identified in the GMC, 54 of which are
supercritical (i.e. ). The mass spectrum of the molecular
clumps follows a power-law distribution with an exponent of . The
pixel-by-pixel column density of the GMC can be fitted with a log-normal
probability distribution function (N-PDF). The median column density of
molecular hydrogen in the GMC is cm and half the mass
of the GMC is contained in regions with H column density lower than
cm, which is well below the threshold of star
formation. The distribution of the YSO candidates in the region shows no
agglomeration.Comment: 24 pages, 18 figure
Modelling carbon-chain species formation in lukewarm corinos with new multi-phase models
Abundant carbon-chain species have been observed towards lukewarm corinos
L1527, B228, and L483. These carbon-chain species are believed to be
synthesized in the gas phase after CH desorbs from the dust grain surface
at the temperature around 30 K. We investigate carbon-chain species formation
in lukewarm corinos using a more rigorous numerical method and advanced surface
chemical models. We use the macroscopic Monte Carlo method in simulations. In
addition to the two-phase model, the basic multiphase model and the new
multiphase models are used for modeling surface chemistry on dust grains. All
volatile species can sublime at their sublimation temperatures in the two-phase
model while most volatile species are frozen in the ice mantle before water ice
sublimes in the basic and the new multiphase models. The new multiphase models
allow more volatile species to sublime at their sublimation temperatures than
the basic multiphase model does. When T 30 K, the abundances of gaseous
CH and CO in the two-phase model are the highest while the basic multiphase
model predicts the lowest CO and CH abundances among all models. The
abundances of carbon-chain species in the basic and the new multiphase models
are lower than that in the two-phase model when T 30 K because CH is
crucial for the synthesis of carbon-chain species. The two-phase model performs
the best to predict carbon-chain species abundances to fit observations while
the basic multiphase model works the worst. The abundances of carbon-chain
species predicted by the new multiphase models agree reasonably well with
observations. The amount of CH that can diffuse inside the ice mantle, thus
sublime upon warm-up plays a crucial role in the synthesis of carbon-chain
species in the gas phase. The carbon-chain species observed in lukewarm corinos
may be able to gauge surface chemical models
Observed spectral energy distribution of the thermal emission from the dayside of WASP-46b
We aim to construct a spectral energy distribution (SED) for the emission
from the dayside atmosphere of the hot Jupiter WASP-46b and to investigate its
energy budget. We observed a secondary eclipse of WASP-46b simultaneously in
the g'r'i'z'JHK bands using the GROND instrument on the MPG/ESO 2.2m telescope.
Eclipse depths of the acquired light curves were derived to infer the
brightness temperatures at multibands that cover the SED peak. We report the
first detection of the thermal emission from the dayside of WASP-46b in the K
band at 4.2-sigma level and tentative detections in the H (2.5-sigma) and J
(2.3-sigma) bands, with flux ratios of 0.253 +0.063/-0.060%, 0.194 +/- 0.078%,
and 0.129 +/- 0.055%, respectively. The derived brightness temperatures (2306
+177/-187K, 2462 +245/-302K, and 2453 +198/-258K, respectively) are consistent
with an isothermal temperature profile of 2386K, which is significantly higher
than the dayside-averaged equilibrium temperature, indicative of very poor heat
redistribution efficiency. We also investigate the tentative detections in the
g'r'i' bands and the 3-sigma upper limit in the z' band, which might indicate
the existence of reflective clouds if these tentative detections do not arise
from systematics.Comment: 8 pages, 7 figures, accepted for publication in A&
Ground-based detection of the near-infrared emission from the dayside of WASP-5b
(Abridged) WASP-5b is a highly irradiated dense hot Jupiter orbiting a G4V
star every 1.6 days. We observed two secondary eclipses of WASP-5b in the J, H
and K bands simultaneously. Thermal emission of WASP-5b is detected in the J
and K bands. The retrieved planet-to-star flux ratios in the J and K bands are
0.168 +0.050/-0.052% and 0.269+/-0.062%, corresponding to brightness
temperatures of 2996 +212/-261K and 2890 +246/-269K, respectively. No thermal
emission is detected in the H band, with a 3-sigma upper limit of 0.166%,
corresponding to a maximum temperature of 2779K. On the whole, our J, H, K
results can be explained by a roughly isothermal temperature profile of ~2700K
in the deep layers of the planetary dayside atmosphere that are probed at these
wavelengths. Together with Spitzer observations, which probe higher layers that
are found to be at ~1900K, a temperature inversion is ruled out in the range of
pressures probed by the combined data set. While an oxygen-rich model is unable
to explain all the data, a carbon-rich model provides a reasonable fit but
violates energy balance.Comment: 13 pages, 9 figures, accepted for publication in A&
Broad-band transmission spectrum and K-band thermal emission of WASP-43b as observed from the ground
(Abridged) We observed one transit and one occultation of the hot Jupiter
WASP-43b simultaneously in the g'r'i'z'JHK bands using the GROND instrument on
the MPG/ESO 2.2-meter telescope. From the transit event, we have independently
derived WASP-43's system parameters with high precision, and improved the
period to be 0.81347437(13) days. No significant variation in transit depths is
detected, with the largest deviations coming from the i', H, and K bands. Given
the observational uncertainties, the broad-band transmission spectrum can be
explained by either a flat featureless straight line that indicates thick
clouds, synthetic spectra with absorption signatures of atomic Na/K or
molecular TiO/VO that indicate cloud-free atmosphere, or a Rayleigh scattering
profile that indicates high-altitude hazes. From the occultation event, we have
detected planetary dayside thermal emission in the K-band with a flux ratio of
0.197 +/- 0.042%, which confirms previous detections obtained in the 2.09
micron narrow band and Ks-band. The K-band brightness temperature 1878
+108/-116 K favors an atmosphere with poor day- to night-side heat
redistribution. We also have a marginal detection in the i'-band (0.037
+0.023/-0.021%), which is either a false positive, a signature of non-blackbody
radiation at this wavelength, or an indication of reflective hazes at high
altitude.Comment: 14 pages, 9 figures, accepted for publication in A&
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