Normalized to: J..
[1]
oai:arXiv.org:1209.3346 [pdf] - 1151421
On the structure of molecular clouds
Submitted: 2012-09-14
We show that the inter-cloud Larson scaling relation between mean volume
density and size $\rho\propto R^{-1}$, which in turn implies that mass
$M\propto R^2$, or that the column density $N$ is constant, is an artifact of
the observational methods used. Specifically, setting the column density
threshold near or above the peak of the column density probability distribution
function Npdf ($N\sim 10^{21}$ cm\alamenos 2) produces the Larson scaling as
long as the Npdf decreases rapidly at higher column densities. We argue that
the physical reasons behind local clouds to have this behavior are that (1)
this peak column density is near the value required to shield CO from
photodissociation in the solar neighborhood, and (2) gas at higher column
densities is rare because it is susceptible to gravitational collapse into much
smaller structures in specific small regions of the cloud. Similarly, we also
use previous results to show that if instead a threshold is set for the volume
density, the density will appear to be constant, implying thus that $M \propto
R^3$. Thus, the Larson scaling relation does not provide much information on
the structure of molecular clouds, and does not imply either that clouds are in
Virial equilibrium, or have a universal structure. We also show that the slope
of the $M-R$ curve for a single cloud, which transitions from near-to-flat
values for large radii to $\alpha=2$ as a limiting case for small radii,
depends on the properties of the Npdf.
[2]
oai:arXiv.org:1012.0782 [pdf] - 1042365
UWISH2 -- The UKIRT Widefield Infrared Survey for H2
D.;
Froebrich;
J., C.;
Davis;
G.;
Ioannidis;
M., T.;
Gledhill;
M.;
Takami;
A.;
Chrysostomou;
J.;
Drew;
J.;
EislÓÆffel;
A.;
Gosling;
R.;
Gredel;
J.;
Hatchell;
W., K.;
Hodapp;
N., M. S.;
Kumar;
W., P.;
Lucas;
H.;
Matthews;
G., M.;
Rawlings;
D., M.;
Smith;
B.;
Stecklum;
P., W.;
Varricatt;
T., H.;
Lee;
S., P.;
Teixeira;
A., C.;
Aspin;
T.;
Khanzadyan;
J.;
Karr;
-J., H.;
Kim;
-C., B.;
Koo;
J., J.;
Lee;
-H., Y.;
Lee;
Y., T.;
Magakian;
A., T.;
Movsessian;
H., E.;
Nikogossian;
S., T.;
Pyo;
T.;
Stanke
Submitted: 2010-12-03
We present the goals and preliminary results of an unbiased, near-infrared,
narrow-band imaging survey of the First Galactic Quadrant (10deg<l<65deg ;
-1.3deg<b<+1.3deg). This area includes most of the Giant Molecular Clouds and
massive star forming regions in the northern hemisphere. The survey is centred
on the 1-0S(1) ro-vibrational line of H2, a proven tracer of hot, dense
molecular gas in star-forming regions, around evolved stars, and in supernova
remnants. The observations complement existing and upcoming photometric surveys
(Spitzer-GLIMPSE, UKIDSS-GPS, JCMT-JPS, AKARI, Herschel Hi-GAL, etc.), though
we probe a dynamically active component of star formation not covered by these
broad-band surveys. Our narrow-band survey is currently more than 60% complete.
The median seeing in our images is 0.73arcsec. The images have a 5sigma
detection limit of point sources of K=18mag and the surface brightness limit is
10^-19Wm^-2arcsec^-2 when averaged over our typical seeing. Jets and outflows
from both low and high mass Young Stellar Objects are revealed, as are new
Planetary Nebulae and - via a comparison with earlier K-band observations
acquired as part of the UKIDSS GPS - numerous variable stars. With their
superior spatial resolution, the UWISH2 data also have the potential to reveal
the true nature of many of the Extended Green Objects found in the GLIMPSE
survey.
[3]
oai:arXiv.org:1012.0782 [pdf] - 1042365
UWISH2 -- The UKIRT Widefield Infrared Survey for H2
D.;
Froebrich;
J., C.;
Davis;
G.;
Ioannidis;
M., T.;
Gledhill;
M.;
Takami;
A.;
Chrysostomou;
J.;
Drew;
J.;
EislÓÆffel;
A.;
Gosling;
R.;
Gredel;
J.;
Hatchell;
W., K.;
Hodapp;
N., M. S.;
Kumar;
W., P.;
Lucas;
H.;
Matthews;
G., M.;
Rawlings;
D., M.;
Smith;
B.;
Stecklum;
P., W.;
Varricatt;
T., H.;
Lee;
S., P.;
Teixeira;
A., C.;
Aspin;
T.;
Khanzadyan;
J.;
Karr;
-J., H.;
Kim;
-C., B.;
Koo;
J., J.;
Lee;
-H., Y.;
Lee;
Y., T.;
Magakian;
A., T.;
Movsessian;
H., E.;
Nikogossian;
S., T.;
Pyo;
T.;
Stanke
Submitted: 2010-12-03
We present the goals and preliminary results of an unbiased, near-infrared,
narrow-band imaging survey of the First Galactic Quadrant (10deg<l<65deg ;
-1.3deg<b<+1.3deg). This area includes most of the Giant Molecular Clouds and
massive star forming regions in the northern hemisphere. The survey is centred
on the 1-0S(1) ro-vibrational line of H2, a proven tracer of hot, dense
molecular gas in star-forming regions, around evolved stars, and in supernova
remnants. The observations complement existing and upcoming photometric surveys
(Spitzer-GLIMPSE, UKIDSS-GPS, JCMT-JPS, AKARI, Herschel Hi-GAL, etc.), though
we probe a dynamically active component of star formation not covered by these
broad-band surveys. Our narrow-band survey is currently more than 60% complete.
The median seeing in our images is 0.73arcsec. The images have a 5sigma
detection limit of point sources of K=18mag and the surface brightness limit is
10^-19Wm^-2arcsec^-2 when averaged over our typical seeing. Jets and outflows
from both low and high mass Young Stellar Objects are revealed, as are new
Planetary Nebulae and - via a comparison with earlier K-band observations
acquired as part of the UKIDSS GPS - numerous variable stars. With their
superior spatial resolution, the UWISH2 data also have the potential to reveal
the true nature of many of the Extended Green Objects found in the GLIMPSE
survey.
[4]
oai:arXiv.org:1012.0782 [pdf] - 1042365
UWISH2 -- The UKIRT Widefield Infrared Survey for H2
D.;
Froebrich;
J., C.;
Davis;
G.;
Ioannidis;
M., T.;
Gledhill;
M.;
Takami;
A.;
Chrysostomou;
J.;
Drew;
J.;
EislÓÆffel;
A.;
Gosling;
R.;
Gredel;
J.;
Hatchell;
W., K.;
Hodapp;
N., M. S.;
Kumar;
W., P.;
Lucas;
H.;
Matthews;
G., M.;
Rawlings;
D., M.;
Smith;
B.;
Stecklum;
P., W.;
Varricatt;
T., H.;
Lee;
S., P.;
Teixeira;
A., C.;
Aspin;
T.;
Khanzadyan;
J.;
Karr;
-J., H.;
Kim;
-C., B.;
Koo;
J., J.;
Lee;
-H., Y.;
Lee;
Y., T.;
Magakian;
A., T.;
Movsessian;
H., E.;
Nikogossian;
S., T.;
Pyo;
T.;
Stanke
Submitted: 2010-12-03
We present the goals and preliminary results of an unbiased, near-infrared,
narrow-band imaging survey of the First Galactic Quadrant (10deg<l<65deg ;
-1.3deg<b<+1.3deg). This area includes most of the Giant Molecular Clouds and
massive star forming regions in the northern hemisphere. The survey is centred
on the 1-0S(1) ro-vibrational line of H2, a proven tracer of hot, dense
molecular gas in star-forming regions, around evolved stars, and in supernova
remnants. The observations complement existing and upcoming photometric surveys
(Spitzer-GLIMPSE, UKIDSS-GPS, JCMT-JPS, AKARI, Herschel Hi-GAL, etc.), though
we probe a dynamically active component of star formation not covered by these
broad-band surveys. Our narrow-band survey is currently more than 60% complete.
The median seeing in our images is 0.73arcsec. The images have a 5sigma
detection limit of point sources of K=18mag and the surface brightness limit is
10^-19Wm^-2arcsec^-2 when averaged over our typical seeing. Jets and outflows
from both low and high mass Young Stellar Objects are revealed, as are new
Planetary Nebulae and - via a comparison with earlier K-band observations
acquired as part of the UKIDSS GPS - numerous variable stars. With their
superior spatial resolution, the UWISH2 data also have the potential to reveal
the true nature of many of the Extended Green Objects found in the GLIMPSE
survey.
[5]
oai:arXiv.org:1012.0782 [pdf] - 1042365
UWISH2 -- The UKIRT Widefield Infrared Survey for H2
D.;
Froebrich;
J., C.;
Davis;
G.;
Ioannidis;
M., T.;
Gledhill;
M.;
Takami;
A.;
Chrysostomou;
J.;
Drew;
J.;
EislÓÆffel;
A.;
Gosling;
R.;
Gredel;
J.;
Hatchell;
W., K.;
Hodapp;
N., M. S.;
Kumar;
W., P.;
Lucas;
H.;
Matthews;
G., M.;
Rawlings;
D., M.;
Smith;
B.;
Stecklum;
P., W.;
Varricatt;
T., H.;
Lee;
S., P.;
Teixeira;
A., C.;
Aspin;
T.;
Khanzadyan;
J.;
Karr;
-J., H.;
Kim;
-C., B.;
Koo;
J., J.;
Lee;
-H., Y.;
Lee;
Y., T.;
Magakian;
A., T.;
Movsessian;
H., E.;
Nikogossian;
S., T.;
Pyo;
T.;
Stanke
Submitted: 2010-12-03
We present the goals and preliminary results of an unbiased, near-infrared,
narrow-band imaging survey of the First Galactic Quadrant (10deg<l<65deg ;
-1.3deg<b<+1.3deg). This area includes most of the Giant Molecular Clouds and
massive star forming regions in the northern hemisphere. The survey is centred
on the 1-0S(1) ro-vibrational line of H2, a proven tracer of hot, dense
molecular gas in star-forming regions, around evolved stars, and in supernova
remnants. The observations complement existing and upcoming photometric surveys
(Spitzer-GLIMPSE, UKIDSS-GPS, JCMT-JPS, AKARI, Herschel Hi-GAL, etc.), though
we probe a dynamically active component of star formation not covered by these
broad-band surveys. Our narrow-band survey is currently more than 60% complete.
The median seeing in our images is 0.73arcsec. The images have a 5sigma
detection limit of point sources of K=18mag and the surface brightness limit is
10^-19Wm^-2arcsec^-2 when averaged over our typical seeing. Jets and outflows
from both low and high mass Young Stellar Objects are revealed, as are new
Planetary Nebulae and - via a comparison with earlier K-band observations
acquired as part of the UKIDSS GPS - numerous variable stars. With their
superior spatial resolution, the UWISH2 data also have the potential to reveal
the true nature of many of the Extended Green Objects found in the GLIMPSE
survey.
[6]
oai:arXiv.org:1009.6065 [pdf] - 1040968
Interpretation of HINODE SOT/SP asymmetric Stokes profiles observed in
quiet Sun network and internetwork
Submitted: 2010-09-30, last modified: 2010-10-01
We present the first interpretation of the Stokes profile asymmetries
measured in the FeI 630 nm lines by SOT/SP, in both quiet Sun internetwork (IN)
and network regions. The inversion is carried out under the hypothesis of
MISMA, where the unresolved structure is assumed to be optically thin. We
analyze a 29.52"x31.70" subfield carefully selected to be representative of the
properties of a 302"x162" quiet Sun field-of-view at disk center. The inversion
code is able to reproduce the observed asymmetries in a very satisfactory way.
The inversion code interprets 25% of inverted profiles as emerging from pixels
in which both positive and negative polarities coexist. kG field strengths are
found at the base of the photosphere in both network and IN; in the case of the
latter, both kG fields and hG fields are admixed. When considering the magnetic
properties at the mid photosphere most kG fields are gone, and the statistics
is dominated by hG fields. We constrain the magnetic field of only 4.5% of the
analyzed photosphere (and this percentage reduces to 1.3% when referred to all
pixels, including those with low polarization not analyzed). The rest of the
plasma is consistent with the presence of weak fields not contributing to the
detected polarization signals. The average flux densities derived in the full
subfield and in IN regions are higher than the ones derived from the same
dataset by Milne-Eddington inversion. The existence of large asymmetries in
SOT/SP polarization profiles is uncovered. These are not negligible in quiet
Sun data. The MISMA inversion code reproduces them in a satisfactory way, and
provides a statistical description of the magnetized IN and network which
partly differs and complements the results obtained so far. From this it
follows the importance of having a complete interpretation of the line profile
shapes.
[7]
oai:arXiv.org:astro-ph/0701578 [pdf] - 88707
Relativistic MHD Winds from Rotating Neutron Stars
Submitted: 2007-01-19
We review here recent numerical results concerning the acceleration and
collimation of relativistic outflows from neutron stars, and we discuss their
implications for models of magnetars in their hypothesized initial high
rotation states. New results with different injection conditions and extending
to much larger distance from the central star are also presented and discussed,
showing that, only in the case of weakly magnetized winds, collimated outflows
are indeed possible. We finally comment on the possibility that newly born
magnetars might trigger GRBs, and we show that numerical results do not support
such hypothesis.