517 research outputs found
Fullerenes, PAHs, Amino Acids and High Energy Astrophysics
We present theoretical, observational and laboratory work on the spectral properties of fullerenes and hydrogenated fullerenes. Fullerenes in its various forms (individual, endohedral, hydrogenated, etc.) can contribute to the UV bump in the extinction curves measured in many lines of sight of the Galaxy. They can also produce a large number of absorption features in the optical and near infrared which could be associated with diffuse interstellar bands. We summarise recent laboratory work on the spectral characterisation of fullerenes and hydrogenated fullerenes (for a range of temperatures). The recent detection of mid-IR bands of fullerenes in various astrophysical environments (planetary nebulae, reflection nebulae) provide additional evidence for a link between fullerene families and diffuse interstellar bands. We describe recent observational work on near IR bands of C60+ in a protoplanetary nebula which support fullerene formation during the post-AGB phase. We also report on the survival of fullerenes to irradiation by high energy particles and gamma photons and laboratory work to explore the chemical reactions that take place when fullerenes are exposed to this radiations in the presence of water, ammonia and other molecules as a potential path to form amino acids
A search for naphthalene in diffuse interstellar clouds
We have obtained high resolution optical spectroscopy of 10 reddened O-type
stars with UVES at VLT to search for interstellar bands of the naphthalene
cation (CH) in the intervening clouds. No absorption features
were detected near the laboratory strongest band of this cation at 6707 \AA
except for star HD 125241 (O9 I). Additional bands in the optical spectrum of
this star appear to be consistent with other transitions of this cation. Under
the assumption that the bands are caused by naphthalene cations we derive a
column density N = (1.2 0.3) x 10 cm similar to
the column density claimed in the Perseus complex star Cernis 52
(Iglesias-Groth et al. 2008). The strength ratio of the two prominent diffuse
interstellar bands at 5780 and 5797 \AA suggests the presence of a
-type cloud in the line of sight of HD 125241.Comment: Accepted for publication in MNRA
A rich molecular chemistry in the gas of the IC 348 star cluster of the Perseus Molecular Cloud
We present Spitzer 10-34 {\mu}m spectroscopic observations of the diffuse gas
in the inner region of the star-forming region IC 348 of the Perseus Molecular
Cloud. We find evidence for the strongest mid-IR bands of common molecules as
H\textsubscript{2}, OH, H\textsubscript{2}O,CO\textsubscript{2} and
NH\textsubscript{3} and of several carbonaceous molecules which may play an
important role in the production of more complex hydrocarbons: HCN,
C\textsubscript{2}H\textsubscript{2}, C\textsubscript{4}H\textsubscript{2},
HC\textsubscript{3}N, HC\textsubscript{5}N,
C\textsubscript{2}H\textsubscript{6}, C\textsubscript{6}H\textsubscript{2},
C\textsubscript{6}H\textsubscript{6}. The excitation diagram of
H\textsubscript{2} reveals the presence of warm gas (270 +- 30 K) at the
observed locations. Assuming this temperature, the derived abundances of
CO\textsubscript{2} and NH\textsubscript{3} relative to H\textsubscript{2} are
10\textsuperscript{-8} and 10\textsuperscript{-7}, respectively. From the water
lines we obtain an abundance of order 10\textsuperscript{-6} and higher gas
temperatures. The abundances derived for HCN and
C\textsubscript{2}H\textsubscript{2}, key molecules in the development of
prebiotic building blocks, are of order 10\textsuperscript{-7} and
10\textsuperscript{-9}, respectively. More complex molecules such as PAHs and
the fullerenes C\textsubscript{60} and C\textsubscript{70} are also present. IC
348 appears to be very rich and diverse in molecular content. The JWST
spectroscopic capabilities may provide details on the spatial distribution of
all these molecules and extend the present search to more complex hydrocarbons.Comment: 33 pages, 24 figures, 4 tables, ACCEPTED in MNRA
A search for interstellar anthracene toward the Perseus anomalous microwave emission region
We report the discovery of a new broad interstellar (or circumstellar) band
at 7088.8 +- 2.0 \AA coincident to within the measurement uncertainties with
the strongest band of the anthracene cation (CH) as measured
in gas-phase laboratory spectroscopy at low temperatures (Sukhorukov et
al.2004). The band is detected in the line of sight of star Cernis 52, a likely
member of the very young star cluster IC 348, and is probably associated with
cold absorbing material in a intervening molecular cloud of the Perseus star
forming region where various experiments have recently detected anomalous
microwave emission. From the measured intensity and available oscillator
strength we find a column density of N= 1.1(+-0.4) x 10
cm implying that ~0.008% of the carbon in the cloud could be in the form
of CH. A similar abundance has been recently claimed for the
naphthalene cation (Iglesias-Groth et al. 2008) in this cloud. This is the
first location outside the Solar System where specific PAHs are identified. We
report observations of interstellar lines of CH and CH that support a
rather high column density for these species and for molecular hydrogen. The
strength ratio of the two prominent diffuse interstellar bands at 5780 and 5797
\AA suggests the presence of a ``zeta'' type cloud in the line of sight
(consistent with steep far-UV extinction and high molecular content). The
presence of PAH cations and other related hydrogenated carbon molecules which
are likely to occur in this type of clouds reinforce the suggestion that
electric dipole radiation from fast spinning PAHs is responsible of the
anomalous microwave emission detected toward Perseus.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical
Societ
The Chemical Composition of Cernis 52 (BD+31 640)
We present an abundance analysis of the star Cernis 52 in whose spectrum we
recently reported the napthalene cation in absorption at 6707.4 {\AA}. This
star is on a line of sight to the Perseus molecular complex. The analysis of
high-resolution spectra using a chi^2-minimization procedure and a grid of
synthetic spectra provides the stellar parameters and the abundances of O, Mg,
Si, S, Ca, and Fe. The stellar parameters of this star are found to be T_{eff}
= 8350 +- 200 K, logg= 4.2 +- 0.4 dex. We derived a metallicity of [Fe/H] =
-0.01 +- 0.15. These stellar parameters are consistent with a star of
\Msun in a pre-main-sequence evolutionary stage. The stellar spectrum is
significantly veiled in the spectral range 5150-6730 {\AA} up to almost 55 per
cent of the total flux at 5150 {\AA} and decreasing towards longer wavelengths.
Using Johnson-Cousins and 2MASS photometric data, we determine a distance to
Cernis 52 of 231 pc considering the error bars of the stellar
parameters. This determination places the star at a similar distance to the
young cluster IC 348. This together with its radial velocity, v_r=13.7+-1 km/s,
its proper motion and probable young age support Cernis 52 as a likely member
of IC 348. We determine a rotational velocity of v\sin i=65 +- 5 km/s for this
star. We confirm that the stellar resonance line of \ion{Li}{1} at 6707.8 {\AA}
is unable to fit the broad feature at 6707.4 {\AA}. This feature should have a
interstellar origin and could possibly form in the dark cloud L1470 surrounding
all the cluster IC 348 at about the same distance.Comment: Accepted for publication in The Astrophysical Journa
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