11,386 research outputs found
Discovering a misaligned CO outflow related to the red MSX source G034.5964-01.0292
The red MSX source G034.5964-01.0292 (MSXG34), catalogued as a massive YSO,
was observed in molecular lines with the aim of discover and study molecular
outflows. We mapped a region of 3'x3' centered at MSXG34 using the Atacama
Submillimeter Telescope Experiment in the 12CO J=3-2 and HCO+ J=4-3 lines with
an angular and spectral resolution of 22" and 0.11 km/s, respectively.
Additionally, public 13CO J=1-0 and near-IR UKIDSS data obtained from the
Galactic Ring Survey and the WFCAM Sciencie Archive, respectively, were
analyzed. We found that the 12CO spectra towards the YSO present a
self-absorption dip, as it is usual in star forming regions, and spectral wings
evidencing outflow activity. The HCO+ was detected only towards the MSXG34
position at v_LSR ~ 14.2 km/s, in coincidence with the 12CO absorption dip and
approximately with the velocity of previous ammonia observations. HCO+ and NH3
are known to be enhanced in molecular outflows. Analyzing the spectral wings of
the 12CO line, we discovered misaligned red- and blue-shifted molecular
outflows associated with MSXG34. The near-IR emission shows a cone-like shape
nebulosity composed by two arc-like features related to the YSO, which can be
due to a cavity cleared in the circumstellar material by a precessing jet. This
can explain the misalignment in the molecular outflows. From the analysis of
the 13CO J=1--0 data we suggest that the YSO is very likely related to a
molecular clump ranging between 10 and 14 km/s. This suggests that MSXG34, with
an associated central velocity of about 14 km/s, may be located in the
background of this clump. Thus, the blue-shifted outflow is probably deflected
by the interaction with dense gas along the line of sight.Comment: Accepted in A&A June 10, 201
Studying the Molecular Ambient towards the Young Stellar Object EGO G35.04-0.47
We are performing a systematic study of the interstellar medium around
extended green objects (EGOs), likely massive young stellar objects driving
outflows. EGO G35.04-0.47 is located towards a dark cloud at the northern-west
edge of an HII region. Recently, H2 jets were discovered towards this source,
mainly towards its southwest, where the H2 1-0 S(1) emission peaks. Therefore,
the source was catalogued as the Molecular Hydrogen emission-line object MHO
2429. In order to study the molecular ambient towards this star-forming site,
we observed a region around the aforementioned EGO using the Atacama
Submillimeter Telescope Experiment in the 12CO J=3--2, 13CO J=3--2, HCO+
J=4--3, and CS J=7--6 lines with an angular and spectral resolution of 22" and
0.11 km s-1, respectively. The observations revealed a molecular clump where
the EGO is embedded at v_LSR ~ 51 km s-1, in coincidence with the velocity of a
Class I 95 GHz methanol maser previously detected. Analyzing the 12CO line we
discovered high velocity molecular gas in the range from 34 to 47 km s-1, most
likely a blueshifted outflow driven by the EGO. The alignment and shape of this
molecular structure coincide with those of the southwest lobe of MHO 2429
mainly between 46 and 47 km s-1, confirming that we are mapping its CO
counterpart. Performing a SED analysis of EGO G35.04-0.47 we found that its
central object should be an intermediate-mass young stellar object accreting
mass at a rate similar to those found in some massive YSOs. We suggest that
this source can become a massive YSO.Comment: accepted to be published in PASJ - 24 September 201
Molecular gas associated with IRAS 10361-5830
We analyze the distribution of the molecular gas and the dust in the
molecular clump linked to IRAS 10361-5830, located in the environs of the
bubble-shaped HII region Gum 31 in the Carina region, with the aim of
determining the main parameters of the associated material and investigating
the evolutionary state of the young stellar objects identified there.
Using the APEX telescope, we mapped the molecular emission in the J=3-2
transition of three CO isotopologues, 12CO, 13CO and C18O, over a 1.5' x 1.5'
region around the IRAS position. We also observed the high density tracers CS
and HCO+ toward the source. The cold dust distribution was analyzed using
submillimeter continuum data at 870 \mu\ obtained with the APEX telescope.
Complementary IR and radio data at different wavelengths were used to complete
the study of the ISM.
The molecular gas distribution reveals a cavity and a shell-like structure of
~ 0.32 pc in radius centered at the position of the IRAS source, with some
young stellar objects (YSOs) projected onto the cavity. The total molecular
mass in the shell and the mean H volume density are ~ 40 solar masses and
~(1-2) x 10 cm, respectively. The cold dust counterpart of the
molecular shell has been detected in the far-IR at 870 \mu\ and in Herschel
data at 350 \mu. Weak extended emission at 24 \mu\ from warm dust is projected
onto the cavity, as well as weak radio continuum emission.
A comparison of the distribution of cold and warm dust, and molecular and
ionized gas allows us to conclude that a compact HII region has developed in
the molecular clump, indicating that this is an area of recent massive star
formation. Probable exciting sources capable of creating the compact HII region
are investigated. The 2MASS source 10380461-5846233 (MSX G286.3773-00.2563)
seems to be responsible for the formation of the HII region.Comment: Accepted in A&A. 11 pages, 10 Postscript figure
12CO and 13CO J=3-2 observations toward N11 in the Large Magellanic Cloud
After 30 Doradus, N11 is the second largest and brightest nebula in the LMC.
This large nebula has several OB associations with bright nebulae at its
surroundings. N11 was previously mapped at the lowest rotational transitions of
CO (J=1--0 and 2--1), and in some particular regions pointings of the
CO J=1--0 and 2--1 lines were also performed. Using ASTE we mapped the
whole extension of the N11 nebula in the CO J=3--2 line, and three
sub-regions in the CO J=3--2 line. The regions mapped in the CO
J=3--2 were selected based on that they may be exposed to the radiation at
different ways: a region lying over the nebula related to the OB association
LH10 (N11B), another one that it is associated with the southern part of the
nebula related to the OB association LH13 (N11D), and finally a farther area at
the southwest without any embedded OB association (N11I). We found that the
morphology of the molecular clouds lying in each region shows some signatures
that could be explained by the expansion of the nebulae and the action of the
radiation. Fragmentation generated in a molecular shell due to the expansion of
the N11 nebula is suggested. The integrated line ratios CO/CO
show evidences of selective photodissociation of the CO, and probably
other mechanisms such as chemical fractionation. The CO contribution to the
continuum at 870 m was directly derived. The distribution of the
integrated line ratios CO J=3--2/2--1 show hints of stellar feedback in
N11B and N11D. The ratio between the virial and LTE mass (M/M) is higher than unity in all analyzed molecular clumps, which suggests
that the clumps are not gravitationally bounded and may be supported by
external pressure. A non-LTE analysis suggests that we are mapping gas with
densities about a few 10 cm.Comment: Accepted to be published in A&A. Figures were degrade
Inelastic lifetimes of hot electrons in real metals
We report a first-principles description of inelastic lifetimes of excited
electrons in real Cu and Al, which we compute, within the GW approximation of
many-body theory, from the knowledge of the self-energy of the excited
quasiparticle. Our full band-structure calculations indicate that actual
lifetimes are the result of a delicate balance between localization, density of
states, screening, and Fermi-surface topology. A major contribution from
-electrons participating in the screening of electron-electron interactions
yields lifetimes of excited electrons in copper that are larger than those of
electrons in a free-electron gas with the electron density equal to that of
valence () electrons. In aluminum, a simple metal with no -bands,
splitting of the band structure over the Fermi level results in electron
lifetimes that are smaller than those of electrons in a free-electron gas.Comment: 4 papes, 2 figures, to appear in Phys. Rev. Let
A view of Large Magellanic Cloud HII regions N159, N132, and N166 through the 345 GHz window
We present results obtained towards the HII regions N159, N166, and N132 from
the emission of several molecular lines in the 345 GHz window. Using ASTE we
mapped a 2.4' 2.4' region towards the molecular cloud N159-W in the
CO J=3-2 line and observed several molecular lines at an IR peak very
close to a massive young stellar object. CO and CO J=3-2 were
observed towards two positions in N166 and one position in N132. The CO
J=3-2 map of the N159-W cloud shows that the molecular peak is shifted
southwest compared to the peak of the IR emission. Towards the IR peak we
detected emission from HCN, HNC, HCO, CH J=4-3, CS J=7-6, and
tentatively CO J=3-2. This is the first reported detection of these
molecular lines in N159-W. The analysis of the CH line yields more
evidence supporting that the chemistry involving this molecular species in
compact and/or UCHII regions in the LMC should be similar to that in Galactic
ones. A non-LTE study of the CO emission suggests the presence of both cool and
warm gas in the analysed region. The same analysis for the CS, HCO, HCN,
and HNC shows that it is very likely that their emissions arise mainly from
warm gas with a density between to some cm. The
obtained HCN/HNC abundance ratio greater than 1 is compatible with warm gas and
with an star-forming scenario. From the analysis of the molecular lines
observed towards N132 and N166 we propose that both regions should have similar
physical conditions, with densities of about 10 cm.Comment: accepted in MNRAS (October 5, 2015
Germanene: a novel two-dimensional Germanium allotrope akin to Graphene and Silicene
Using a gold (111) surface as a substrate we have grown in situ by molecular
beam epitaxy an atom-thin, ordered, two-dimensional multi-phase film. Its
growth bears strong similarity with the formation of silicene layers on silver
(111) templates. One of the phases, forming large domains, as observed in
Scanning Tunneling Microscopy, shows a clear, nearly flat, honeycomb structure.
Thanks to thorough synchrotron radiation core-level spectroscopy measurements
and advanced Density Functional Theory calculations we can identify it to a
xR(30{\deg}) germanene layer in coincidence with a
xR(19.1{\deg}) Au(111) supercell, thence, presenting the
first compelling evidence of the birth of a novel synthetic germanium-based
cousin of graphene.Comment: 16 pages, 4 figures, 1 tabl
ASTE observations in the 345 GHz window towards the HII region N113 of the Large Magellanic Cloud
N113 is an HII region located in the central part of the Large Magellanic
Cloud (LMC) with an associated molecular cloud very rich in molecular species.
Most of the previously observed molecular lines cover the frequency range
85-270 GHz. Thus, a survey and study of lines at the 345 GHz window is required
in order to have a more complete understanding of the chemistry and excitation
conditions of the region. We mapped a region of 2.5' x 2.5' centered at N113
using the Atacama Submillimeter Telescope Experiment in the 13CO J=3-2 line
with an angular and spectral resolution of 22" and 0.11 km/s, respectively. In
addition, we observed 16 molecular lines as single pointings towards its
center. For the molecular cloud associated with N113, from the 13CO J=3-2 map
we estimate LTE and virial masses of about 1x10^4 and 4.5x10^4 M_sun,
respectively. Additionally, from the dust continuum emission at 500 micron we
obtain a mass of gas of 7x10^3 M_sun. Towards the cloud center we detected
emission from: 12CO, 13CO, C18O (3-2), HCN, HNC, HCO+, C2H (4-3), and CS (7-6);
being the first reported detection of HCN, HNC, and C2H (4-3) lines from this
region. The CS (7-6) which was previously tentatively detected is confirmed in
this study. By analyzing the HCN, HNC, and C2H, we suggest that their emission
may arise from a photodissociation region (PDR). Moreover, we suggest that the
chemistry involving the C2H in N113 can be similar to that in Galactic PDRs.
Using the HCN J=4-3, J=3-2, and J=1-0 lines in a RADEX analysis we conclude
that we are observing very high density gas, between some 10^5 and 10^7 cm-3.Comment: accepted for publication in A&A, September 9, 201
High Excitation Molecular Gas in the Magellanic Clouds
We present the first survey of submillimeter CO 4-3 emission in the
Magellanic Clouds. The survey is comprised of 15 6'x6' maps obtained using the
AST/RO telescope toward the molecular peaks of the Large and Small Magellanic
Clouds. We have used these data to constrain the physical conditions in these
objects, in particular their molecular gas density and temperature. We find
that there are significant amounts of molecular gas associated with most of
these molecular peaks, and that high molecular gas temperatures are pervasive
throughout our sample. We discuss whether this may be due to the low
metallicities and the associated dearth of gas coolants in the Clouds, and
conclude that the present sample is insufficient to assert this effect.Comment: 18 pages, 3 figures, 5 tables. To appear in Ap
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