573 research outputs found
CO excitation in the Seyfert galaxy NGC 34: stars, shock or AGN driven?
We present a detailed analysis of the X-ray and molecular gas emission in the
nearby galaxy NGC 34, to constrain the properties of molecular gas, and assess
whether, and to what extent, the radiation produced by the accretion onto the
central black hole affects the CO line emission. We analyse the CO Spectral
Line Energy Distribution (SLED) as resulting mainly from Herschel and ALMA
data, along with X-ray data from NuSTAR and XMM-Newton. The X-ray data analysis
suggests the presence of a heavily obscured AGN with an intrinsic luminosity of
L erg s. ALMA high
resolution data () allows us to scan the nuclear region
down to a spatial scale of pc for the CO(6-5) transition. We
model the observed SLED using Photo-Dissociation Region (PDR), X-ray-Dominated
Region (XDR), and shock models, finding that a combination of a PDR and an XDR
provides the best fit to the observations. The PDR component, characterized by
gas density and temperature K,
reproduces the low-J CO line luminosities. The XDR is instead characterised by
a denser and warmer gas (, K), and is
necessary to fit the high-J transitions. The addition of a third component to
account for the presence of shocks has been also tested but does not improve
the fit of the CO SLED. We conclude that the AGN contribution is significant in
heating the molecular gas in NGC 34.Comment: Accepted for publication in MNRAS. 10 pages, 6 figure
Are z>2 Herschel galaxies proto-spheroids?
We present a backward approach for the interpretation of the evolution of the
near-infrared and the far-infrared luminosity functions across the redshift
range 0<z<3. In our method, late-type galaxies are treated by means of a
parametric phenomenological method based on PEP/HerMES data up to z~4, whereas
spheroids are described by means of a physically motivated backward model. The
spectral evolution of spheroids is modelled by means of a single-mass model,
associated to a present-day elliptical with K-band luminosity comparable to the
break of the local early-type luminosity function. The formation of
proto-spheroids is assumed to occurr across the redshift range 1< z < 5. The
key parameter is represented by the redshift z_0.5 at which half
proto-spheroids are already formed. A statistical study indicates for this
parameter values between z_0.5=1.5 and z_0.5=3. We assume as fiducial value
z_0.5~2, and show that this assumption allows us to describe accourately the
redshift distributions and the source counts. By assuming z_0.5 ~ 2 at the
far-IR flux limit of the PEP-COSMOS survey, the PEP-selected sources observed
at z>2 can be explained as progenitors of local spheroids caught during their
formation. We also test the effects of mass downsizing by dividing the
spheroids into three populations of different present-day stellar masses. The
results obtained in this case confirm the validity of our approach, i.e. that
the bulk of proto-spheroids can be modelled by means of a single model which
describes the evolution of galaxies at the break of the present-day early type
K-band LF.Comment: Accepted for publication in ApJ; 26 pages; 13 figure
Handheld Standoff Mine Detection System (HSTAMIDS) Operational Field Evaluation in Cambodia
Handheld Standoff Mine Detection System (HSTAMIDS) Operational Field Evaluation in Cambodi
Nowcasting of Earthquake Consequences Using Big Social Data
Messages posted to social media in the aftermath of a natural disaster have value beyond detecting the event itself. Mining such deliberately dropped digital traces allows a precise situational awareness, to help provide a timely estimate of the disaster’s consequences on the population and infrastructures. Yet, to date, the automatic assessment of damage has received little attention. Here, the authors explore feeding predictive models by tweets conveying on-the-ground social sensors’ observations, to nowcast the perceived intensity of earthquakes
Constraint on the Assembly and Dynamics of Galaxies. II. Properties of Kiloparsec-Scale Clumps in Rest-Frame Optical Emission of z ~ 2 Star-Forming Galaxies
We study the properties of luminous stellar "clumps" identified in deep, high-resolution Hubble Space Telescope NIC2/F160W imaging at 1.6 μm of six z ~ 2 star-forming galaxies with existing near-infrared integral field spectroscopy from SINFONI at the Very Large Telescope. Individual clumps contribute ~0.5%-15% of the galaxy-integrated rest-frame ≈5000 Å emission, with median of ≈2%; the total contribution of clump light ranges from 10% to 25%. The median intrinsic clump size and stellar mass are ~1 kpc and ~10^9 M_☉, in the ranges for clumps identified in rest-UV or line emission in other studies. The clump sizes and masses in the subset of disks are broadly consistent with expectations for clump formation through gravitational instabilities in gas-rich, turbulent disks given the host galaxies' global properties. By combining the NIC2 data with Advanced Camera for Surveys (ACS)/F814W imaging available for one source, and adaptive-optics-assisted SINFONI Hα data for another, we infer modest color, M/L, and stellar age variations within each galaxy. In these two objects, sets of clumps identified at different wavelengths do not fully overlap; NIC2-identified clumps tend to be redder/older than ACS- or Hα-identified clumps without rest-frame optical counterparts. There is evidence for a systematic trend of older ages at smaller galactocentric radii among the clumps, consistent with scenarios where inward migration of clumps transports material toward the central regions. From constraints on a bulge-like component at radii ≾1-3 kpc, none of the five disks in our sample appears to contain a compact massive stellar core, and we do not discern a trend of bulge stellar mass fraction with stellar age of the galaxy. Further observations are necessary to probe the buildup of stellar bulges and the role of clumps in this process
In vitro evaluation on HeLa cells of protective mechanisms of probiotic lactobacilli against Candida clinical isolates
Aims: To characterize in vitro the ability of human Lactobacillus strains to inhibit the adhesion, to displace and to compete with clinically isolated Candida strains.
Methods and Results: Three types of assays were performed to determine the inhibitory effect of Lactobacillus plantarum 319, Lactobacillus rhamnosus IMC 501, Lactobacillus paracasei IMC 502 and a specific probiotic combination
(SYNBIO) on adhesion of Candida pathogens to HeLa cells: blockage by exclusion (lactobacilli and HeLa followed by pathogens), competition (lactobacilli, HeLa and pathogens together) and displacement (pathogens and HeLa followed by the addition of lactobacilli). Bacterial adhesion to HeLa was quantified by microscopy after May-Grunwald/Giemsa stain. The inhibition results highlight a significant (P < 0.05) competition of the considered probiotics against all the Candida strains. The results suggest that the probiotic strains used in this study could prevent colonization of the urogenital tract by
relevant pathogens such as Candida strains through barrier and interference mechanisms (mainly displacement and competition), but the degree of inhibition of adhesion was bacterial strain-dependent.
Conclusions: The results support the potential of these Lactobacillus probiotic strains as anti-infective agents in the vagina and encourage further studies about their capacity to prevent and manage urogenital tract infections in females.
Significance and Impact of the Study: To optimize the defensive properties of the vaginal microbiota, improving the health of many women by probiotic intervention
Blowin' in the wind: both `negative' and `positive' feedback in an obscured high-z Quasar
Quasar feedback in the form of powerful outflows is invoked as a key
mechanism to quench star formation in galaxies, preventing massive galaxies to
over-grow and producing the red colors of ellipticals. On the other hand, some
models are also requiring `positive' AGN feedback, inducing star formation in
the host galaxy through enhanced gas pressure in the interstellar medium.
However, finding observational evidence of the effects of both types of
feedback is still one of the main challenges of extragalactic astronomy, as few
observations of energetic and extended radiatively-driven winds are available.
Here we present SINFONI near infrared integral field spectroscopy of XID2028,
an obscured, radio-quiet z=1.59 QSO detected in the XMM-COSMOS survey, in which
we clearly resolve a fast (1500 km/s) and extended (up to 13 kpc from the black
hole) outflow in the [OIII] lines emitting gas, whose large velocity and
outflow rate are not sustainable by star formation only. The narrow component
of Ha emission and the rest frame U band flux from HST-ACS imaging enable to
map the current star formation in the host galaxy: both tracers independently
show that the outflow position lies in the center of an empty cavity surrounded
by star forming regions on its edge. The outflow is therefore removing the gas
from the host galaxy (`negative feedback'), but also triggering star formation
by outflow induced pressure at the edges (`positive feedback'). XID2028
represents the first example of a host galaxy showing both types of feedback
simultaneously at work.Comment: 9 pages, 5 figures, accepted for publication in Ap
False and true pre-treatment predictors of weight loss in obese patients starting a program for lifestyle change.
Evidence for feedback in action from the molecular gas content in the z~1.6 outflowing QSO XID2028
Gas outflows are believed to play a pivotal role in shaping galaxies, as they regulate both star formation and black hole growth. Despite their ubiquitous presence, the origin and the acceleration mechanism of such powerful and extended winds is not yet understood. Direct observations of the cold gas component in objects with detected outflows at other wavelengths are needed to assess the impact of the outflow on the host galaxy interstellar medium (ISM). We observed with the Plateau de Bure Interferometer an obscured quasar at z~1.5, XID2028, for which the presence of an ionised outflow has been unambiguously signalled by NIR spectroscopy. The detection of CO(3-2) emission in this source allows us to infer the molecular gas content and compare it to the ISM mass derived from the dust emission. We then analyze the results in the context of recent insights on scaling relations, which describe the gas content of the overall population of star-forming galaxies at a similar redshifts. The Star formation efficiency (~100) and gas mass (M_gas=2.1-9.5x10^{10} M_sun) inferred from the CO(3-2) line depend on the underlying assumptions on the excitation of the transition and the CO-to-H2 conversion factor. However, the combination of this information and the ISM mass estimated from the dust mass suggests that the ISM/gas content of XID2028 is significantly lower than expected for its observed M⋆, sSFR and redshift, based on the most up-to-date calibrations (with gas fraction <20% and depletion time scale <340 Myr). Overall, the constraints we obtain from the far infrared and millimeter data suggest that we are observing QSO feedback able to remove the gas from the host
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