1,273 research outputs found
CO map and steep Kennicutt-Schmidt relation in the extended UV disk of M63
Results from the UV satellite GALEX revealed large extensions of disks in
some nearby spiral galaxies, extending out to 3 to 4 times the isophotal
radius, r25. M63 is a remarkable example of a spiral galaxy with one of the
most extended UV disks, so it offers the opportunity to search for the
molecular gas and characterize the star formation in outer disk regions as
revealed by the UV emission. We obtained deep CO(1-0) and CO(2-1) observations
on the IRAM 30 m telescope along the major axis of the M63 disk from the center
out to the galactocentric radius rgal = 1.6 r25 and over a bright UV region at
rgal = 1.36 r25. CO(1-0) is detected all along the M63 major axis out to r25,
and CO(2-1) is confined to rgal = 0.68 r25, which may betray lower excitation
temperatures in the outer disk. CO(1-0) is also detected in the external bright
UV region of M63. The radial profiles of the CO emission and of the Halpha, 24
micron, NUV and FUV star formation tracers and HI taken from the literature
show a severe drop with the galactocentric radius, such that beyond r25 they
are all absent with the exception of a faint UV emission and HI. The CO
emission detection in the external UV region, where the UV flux is higher than
the UV flux observed beyond r25, highlights a tight correlation between the CO
and UV fluxes, namely the amount of molecular gas and the intensity of star
formation. This external UV region is dominated by the atomic gas, suggesting
that HI is more likely the precursor of H2 rather than the product of UV
photodissociation. A broken power law needs to be invoked to describe the
Kennicutt-Schmidt (K-S) relation of M63 from the center of the galaxy out to
rgal = 1.36 r25. While all along the major axis out to r25 the K-S relation is
almost linear, in the external UV region the SFR regime is highly nonlinear and
characterized by a steep K-S relation and very low star formation efficiency.Comment: 12 pages, 8 figures, A&A accepte
Crises, Labor Market Policy, and Unemployment
Using a sample of 97 countries spanning the period 1980?2008, we estimate that financial crises have a large negative impact on unemployment in the short term, but that this effect rapidly disappears in the medium term in countries with flexible labor market institutions, whereas the impact of financial crises is less pronounced but more persistent in countries with more rigid labor market institutions. These effects are even larger for youth unemployment in the short term and long-term unemployment in the medium term. Conversely, large upfront, or gradual but significant, comprehensive labor market policies have a positive impact on unemployment, albeit only in the medium term
A Five-year Spectroscopic and Photometric Campaign on the Prototypical alpha Cygni Variable and A-type Supergiant Star Deneb
Deneb is often considered the prototypical A-type supergiant, and is one of
the visually most luminous stars in the Galaxy. A-type supergiants are
potential extragalactic distance indicators, but the variability of these stars
needs to be better characterized before this technique can be considered
reliable. We analyzed 339 high resolution echelle spectra of Deneb obtained
over the five-year span of 1997 through 2001 as well as 370 Stromgren
photometric measurements obtained during the same time frame. Our spectroscopic
analysis included dynamical spectra of the H-alpha profile, H-alpha equivalent
widths, and radial velocities measured from Si II 6347, 6371. Time-series
analysis reveals no obvious cyclic behavior that proceeds through multiple
observing seasons, although we found a suspected 40 day period in two,
non-consecutive observing seasons. Some correlations are found between
photometric and radial velocity data sets, and suggest radial pulsations at two
epochs. No correlation is found between the variability of the H-alpha profiles
and that of the radial velocities or the photometry. Lucy (1976) found evidence
that Deneb was a long period single-lined spectroscopic binary star, but our
data set shows no evidence for radial velocity variations caused by a binary
companion.Comment: 49 pages, 9 figures, 5 tables, accepted for publication in the
Astronomical Journa
Multiwavelength Study of NGC 281 Region
We present a multiwavelength study of the NGC 281 complex which contains the
young cluster IC 1590 at the center, using deep wide-field optical UBVI_c
photometry, slitless spectroscopy along with archival data sets in the
near-infrared (NIR) and X-ray. The extent of IC 1590 is estimated to be ~6.5
pc. The cluster region shows a relatively small amount of differential
reddening. The majority of the identified young stellar objects (YSOs) are low
mass PMS stars having age <1-2 Myr and mass 0.5-3.5 M_\odot. The slope (\Gamma)
of the mass function for IC 1590, in the mass range 2 < M/M_\odot \le 54, is
found to be -1.11+-0.15. The slope of the K-band luminosity function
(0.37+-0.07) is similar to the average value (~0.4) reported for young
clusters. The distribution of gas and dust obtained from the IRAS, CO and radio
maps indicates clumpy structures around the central cluster. The radial
distribution of the young stellar objects, their ages, \Delta(H-K) NIR-excess,
and the fraction of classical T Tauri stars suggest triggered star formation at
the periphery of the cluster region. However, deeper optical, NIR and MIR
observations are needed to have a conclusive view of star formation scenario in
the region. The properties of the Class 0/I and Class II sources detected by
using the Spitzer mid-infrared observations indicate that a majority of the
Class II sources are X-ray emitting stars, whereas X-ray emission is absent
from the Class 0/I sources. The spatial distribution of Class 0/I and Class II
sources reveals the presence of three sub-clusters in the NGC 281 West region.Comment: 29 pages, 21 figures and 11 tables, Accepted for the publication in
PAS
A Light Calibration System for the ProtoDUNE-DP Detector
A LED-based fiber calibration system for the ProtoDUNE-Dual Phase (DP) photon
detection system (PDS) has been designed and validated. ProtoDUNE-DP is a 6x6x6
m3 liquid argon time-projection-chamber currently being installed at the
Neutrino Platform at CERN. The PDS is based on 36 8-inch photomultiplier tubes
(PMTs) and will allow triggering on cosmic rays. The system serves as prototype
for the PDS of the final DUNE DP far detector in which the PDS also has the
function to allow the 3D event reconstruction on non-beam physics. For this
purpose an equalized PMT response is desirable to allow using the same
threshold definition for all PMT groups, simplifying the determination of the
trigger efficiency. The light calibration system described in this paper is
developed to provide this and to monitor the PMT performance in-situ.Comment: 15 pages, 5 figure
Design of a Statistical Strategy to the Control of a Fluidized Bed Equipped with a Rotating Distributor
- …