18 research outputs found
The 492 GHz emission of Sgr A* constrained by ALMA
We report linearly polarized continuum emission properties of Sgr A* at
492 GHz, based on the Atacama Large Millimeter Array (ALMA) observations.
We used the observations of the likely unpolarized continuum emission of Titan,
and the observations of C\textsc{i} line emission, to gauge the degree of
spurious polarization. The Stokes I flux of 3.60.72 Jy during our run is
consistent with extrapolations from the previous, lower frequency observations.
We found that the continuum emission of Sgr A* at 492 GHz shows large
amplitude differences between the XX and the YY correlations. The observed
intensity ratio between the XX and YY correlations as a function of parallactic
angle may be explained by a constant polarization position angle of
1583. The fitted polarization percentage of Sgr
A* during our observational period is 14\%1.2\%. The calibrator quasar
J1744-3116 we observed at the same night can be fitted to Stokes I = 252 mJy,
with 7.9\%0.9\% polarization in position angle P.A. =
4.14.2. The observed polarization percentage and
polarization position angle in the present work appear consistent with those
expected from longer wavelength observations in the period of 1999-2005. In
particular, the polarization position angle at 492 GHz, expected from the
previously fitted 1677 intrinsic polarization position
angle and (-5.60.7)10 rotation measure, is 155,
which is consistent with our new measurement of polarization position angle
within 1. The polarization percentage and the polarization position
angle may be varying over the period of our ALMA 12m Array observations, which
demands further investigation with future polarization observations.Comment: 10 pages, 6 figures, 1st referee report received and revise
CARMA CO(J = 2 - 1) Observations of the Circumstellar Envelope of Betelgeuse
We report radio interferometric observations of the 12C16O 1.3 mm J = 2-1
emission line in the circumstellar envelope of the M supergiant Alpha Ori and
have detected and separated both the S1 and S2 flow components for the first
time. Observations were made with the Combined Array for Research in
Millimeter-wave Astronomy (CARMA) interferometer in the C, D, and E antenna
configurations. We obtain good u-v coverage (5-280 klambda) by combining data
from all three configurations allowing us to trace spatial scales as small as
0.9\arcsec over a 32\arcsec field of view. The high spectral and spatial
resolution C configuration line profile shows that the inner S1 flow has
slightly asymmetric outflow velocities ranging from -9.0 km s-1 to +10.6 km s-1
with respect to the stellar rest frame. We find little evidence for the outer
S2 flow in this configuration because the majority of this emission has been
spatially-filtered (resolved out) by the array. We also report a SOFIA-GREAT
CO(J= 12-11) emission line profile which we associate with this inner higher
excitation S1 flow. The outer S2 flow appears in the D and E configuration maps
and its outflow velocity is found to be in good agreement with high resolution
optical spectroscopy of K I obtained at the McDonald Observatory. We image both
S1 and S2 in the multi-configuration maps and see a gradual change in the
angular size of the emission in the high absolute velocity maps. We assign an
outer radius of 4\arcsec to S1 and propose that S2 extends beyond CARMA's field
of view (32\arcsec at 1.3 mm) out to a radius of 17\arcsec which is larger than
recent single-dish observations have indicated. When azimuthally averaged, the
intensity fall-off for both flows is found to be proportional to R^{-1}, where
R is the projected radius, indicating optically thin winds with \rho \propto
R^{-2}.Comment: 11 pages, 8 figures To be published in the Astronomical Journal
(Received 2012 February 10; accepted 2012 May 25
H2CN/H2NC abundance ratio: a new potential temperature tracer for the interstellar medium
The radical is the high-energy metastable isomer of radical, which has been recently detected for the first time in the
interstellar medium towards a handful of cold galactic sources, besides a warm
galaxy in front of the PKS 1830-211 quasar. These detections have shown that
the / isomeric ratio, likewise the HCN/HNC ratio,
might increase with the kinetic temperature (), but the shortage
of them in warm sources still prevents us to confirm this hypothesis and shed
light about their chemistry. In this work, we present the first detection of
and towards a warm galactic source, the
G+0.693-0.027 molecular cloud (with ), using IRAM
30m observations. We have detected multiple hyperfine components of the
and transitions.
We derived molecular abundances with respect to of
(6.81.3) for and of (3.10.7) for , and a / abundance ratio
of 2.20.5. These detections confirm that the /
ratio is 2 for sources with , larger than
the 1 ratios previously found in colder cores (). This isomeric ratio dependence with temperature cannot be fully explained
with the currently proposed gas-phase formation and destruction pathways. Grain
surface reactions, including the
isomerization, deserve consideration to explain the higher isomeric ratios and
abundances observed in warm sources, where the molecules can be
desorbed into the gas phase through thermal and/or shock-induced mechanisms.Comment: 12 pages, 5 figures, 3 tables, 2 appendix - Accepted for publication
in Monthly Notices of the Royal Astronomical Societ
Discovery of the elusive carbonic acid (HOCOOH) in space
After a quarter century since the detection of the last interstellar
carboxylic acid, acetic acid (CHCOOH), we report the discovery of a new
one, the cis-trans form of carbonic acid (HOCOOH), toward the Galactic Center
molecular cloud G+0.693-0.027. HOCOOH stands as the first interstellar molecule
containing three oxygen atoms and also the third carboxylic acid detected so
far in the interstellar medium. Albeit the limited available laboratory
measurements (up to 65 GHz), we have also identified several pairs of unblended
lines directly in the astronomical data (between 75-120 GHz), which allowed us
to slightly improve the set of spectroscopic constants. We derive a column
density for cis-trans HOCOOH of = (6.4 0.4) 10
cm, which yields an abundance with respect to molecular H of 4.7
10. Meanwhile, the extremely low dipole moment (about fifteen
times lower) of the lower-energy conformer, cis-cis HOCOOH, precludes its
detection. We obtain an upper limit to its abundance with respect to H of
1.2 10, which suggests that cis-cis HOCOOH might be
fairly abundant in interstellar space, although it is nearly undetectable by
radio astronomical observations. We derive a cis-cis/cis-trans ratio 25,
consistent with the smaller energy difference between both conformers compared
with the relative stability of trans- and cis-formic acid (HCOOH). Finally, we
compare the abundance of these acids in different astronomical environments,
further suggesting a relationship between the chemical content found in the
interstellar medium and the chemical composition of the minor bodies of the
Solar System, which could be inherited during the star formation process.Comment: Accepted for publication in The Astrophysical Journa
First glycine isomer detected in the interstellar medium: glycolamide (NHC(O)CHOH)
We report the first detection in the interstellar medium of a
CHON isomer: -glycolamide (NHC(O)CHOH). The exquisite
sensitivity at sub-mK levels of an ultra-deep spectral survey carried out with
the Yebes 40m and IRAM 30m telescopes towards the G+0.693-0.027 molecular cloud
have allowed us to unambiguously identify multiple transitions of this species.
We derived a column density of (7.4 0.7)10 cm,
which implies a molecular abundance with respect to H of
5.510. The other CHON isomers, including the
higher-energy conformer of glycolamide, and two conformers of glycine,
were not detected. The upper limit derived for the abundance of glycine
indicates that this amino acid is surely less abundant than its isomer
glycolamide in the ISM. The abundances of the CHON isomers cannot
be explained in terms of thermodynamic equilibrium, and thus chemical kinetics
need to be invoked. While the low abundance of glycine might not be surprising,
based on the relative low abundances of acids in the ISM compared to other
compounds (e.g. alcohols, aldehydes or amines), several chemical pathways can
favour the formation of its isomer glycolamide. It can be formed through
radical-radical reactions on the surface of dust grains. The abundances of
these radicals can be significantly boosted in an environment affected by a
strong ultraviolet field induced by cosmic rays, such as that expected in
G+0.693-0.027. Therefore, as shown by several recent molecular detections
towards this molecular cloud, it stands out as the best target to discover new
species with carbon, oxygen and nitrogen with increasing chemical complexity.Comment: Accepted in The Astrophysical Journal Letter
Precursors of fatty alcohols in the ISM: Discovery of n-propanol
Theories on the origins of life propose that early cell membranes were
synthesized from amphiphilic molecules simpler than phospholipids such as fatty
alcohols. The discovery in the interstellar medium (ISM) of ethanolamine, the
simplest phospholipid head group, raises the question whether simple
amphiphilic molecules are also synthesized in space. We investigate whether
precursors of fatty alcohols are present in the ISM. For this, we have carried
out a spectral survey at 7, 3, 2 and 1 mm toward the Giant Molecular Cloud
G+0.693-0.027 located in the Galactic Center using the IRAM 30m and Yebes 40m
telescopes. Here, we report the detection in the ISM of the primary alcohol
n-propanol (in both conformers Ga-n-C3H7OH and Aa-n-C3H7OH), a precursor of
fatty alcohols. The derived column densities of n-propanol are (5.5+-0.4)x10^13
cm^-2 for the Ga conformer and (3.4+-0.3)x10^13 cm^-2 for the Aa conformer,
which imply molecular abundances of (4.1+-0.3)x10^-10 for Ga-n-C3H7OH and of
(2.5+-0.2)x10^-10 for Aa-n-C3H7OH. We also searched for the AGa conformer of
n-butanol (AGa-n-C4H9OH) without success yielding an upper limit to its
abundance of <4.1x10^-11. The inferred CH3OH:C2H5OH:C3H7OH:C4H9OH abundance
ratios go as 1:0.04:0.006:<0.0004 toward G+0.693-0.027, i.e. they decrease
roughly by one order of magnitude for increasing complexity. We also report the
detection of both syn and anti conformers of vinyl alcohol, with column
densities of (1.11+-0.08)x10^14 cm^-2 and (1.3+-0.4)x10^13 cm^-2, and
abundances of (8.2+-0.6)x10^-10 and (9.6+-3.0)x10^-11, respectively. The
detection of n-propanol, together with the recent discovery of ethanolamine in
the ISM, opens the possibility that precursors of lipids according to theories
of the origin of life, could have been brought to Earth from outer space.Comment: 15 pages, 10 figures, accepted for A&
Precursors of the RNA-world in space: Detection of ()-1,2-ethenediol in the interstellar medium, a key intermediate in sugar formation
We present the first detection of ()-1,2-ethenediol, (CHOH), the enol
form of glycolaldehyde, in the interstellar medium towards the G+0.693-0.027
molecular cloud located in the Galactic Center. We have derived a column
density of (1.80.1)10 cm, which translates into a
molecular abundance with respect to molecular hydrogen of
1.310. The abundance ratio between glycolaldehyde and
()-1,2-ethenediol is 5.2. We discuss several viable formation routes
through chemical reactions from precursors such as HCO, HCO, CHOH or
CHCHOH. We also propose that this species might be an important precursor
in the formation of glyceraldehyde (HOCHCHOHCHO) in the interstellar medium
through combination with the hydroxymethylene (CHOH) radical.Comment: Accepted for publication in The Astrophysical Journal Letter
A nutritional intervention study with hydrolyzed collagen in pre-pubertal Spanish children: influence on bone modeling biomarkers
Journal Article; Randomized Controlled Trial.Aim: The aim of the study was to investigate the influence of dietary intake of commercial hydrolyzed collagen (Gelatine Royal Âź) on bone remodeling in pre-pubertal children.
Methods: A randomized double-blind study was carried out in 60 children (9.42 ± 1.31 years) divided into three groups according to the amount of partially hydrolyzed collagen taken daily for 4 months: placebo (G-I, n = 18), collagen (G-II, n = 20) and collagen + calcium (G-III, n = 22) groups. Analyses of the following biochemical markers were carried out: total and bone alkaline phosphatase (tALP and bALP), osteocalcin, tartrate-resistant acid phosphatase (TRAP), type I collagen carboxy terminal telopeptide, lipids, calcium, 25-hydroxyvitamin D, insulin-like growth factor 1 (IGF-1), thyroid-stimulating hormone, free thyroxin and intact parathormone.
Results: There was a significantly greater increase in serum IGF-1 in G-III than in G II (p < 0.01) or G-I (p < 0.05) during the study period, and a significantly greater increase in plasma tALP in G-III than in G-I (p < 0.05). Serum bALP behavior significantly (p < 0.05) differed between G-II (increase) and G-I (decrease). Plasma TRAP behavior significantly differed between G-II and G-I (p < 0.01) and between G-III and G-II (p < 0.05).
Conclusion: Daily dietary intake of hydrolyzed collagen seems to have a potential role in enhancing bone remodeling at key stages of growth and development.Ye