143 research outputs found
The dust and cold gas content of local star forming galaxies
We use dust masses () derived from far-infrared data and molecular
gas masses () based on CO luminosity, to calibrate proxies based on a
combination of the galaxy Balmer decrement, disk inclination and gas
metallicity. We use such proxies to estimate and in the
local SDSS sample of star-forming galaxies (SFGs). We study the distribution of
and along and across the Main Sequence (MS) of SFGs. We
find that and increase rapidly along the MS with
increasing stellar mass (), and more marginally across the MS with
increasing SFR (or distance from the relation). The dependence on is
sub-linear for both and . Thus, the fraction of dust
() and molecular gas mass () decreases monotonically towards
large . The star formation efficiency (SFE, the inverse of the molecular
gas depletion time) depends strongly on the distance from the MS and it is
constant along the MS. As nearly all galaxies in the sample are central
galaxies, we estimate the dependence of and on the host
halo mass and find a tight anti-correlation. As the region where the MS is
bending is numerically dominated by massive halos, we conclude that the bending
of the MS is due to lower availability of molecular gas mass in massive halos
rather than a lower efficiency in forming stars.Comment: Accepted for publication in MNRAS, 12 pages, 9 figure
The gravitational mass of Proxima Centauri measured with SPHERE from a microlensing event
Proxima Centauri, our closest stellar neighbour, is a low-mass M5 dwarf
orbiting in a triple system. An Earth-mass planet with an 11 day period has
been discovered around this star. The star's mass has been estimated only
indirectly using a mass-luminosity relation, meaning that large uncertainties
affect our knowledge of its properties. To refine the mass estimate, an
independent method has been proposed: gravitational microlensing. By taking
advantage of the close passage of Proxima Cen in front of two background stars,
it is possible to measure the astrometric shift caused by the microlensing
effect due to these close encounters and estimate the gravitational mass of the
lens (Proxima Cen). Microlensing events occurred in 2014 and 2016 with impact
parameters, the closest approach of Proxima Cen to the background star, of
1\farcs6 0\farcs1 and 0\farcs5 0\farcs1, respectively. Accurate
measurements of the positions of the background stars during the last two years
have been obtained with HST/WFC3, and with VLT/SPHERE from the ground. The
SPHERE campaign started on March 2015, and continued for more than two years,
covering 9 epochs. The parameters of Proxima Centauri's motion on the sky,
along with the pixel scale, true North, and centering of the instrument
detector were readjusted for each epoch using the background stars visible in
the IRDIS field of view. The experiment has been successful and the astrometric
shift caused by the microlensing effect has been measured for the second event
in 2016. We used this measurement to derive a mass of
0.150 (an error of 40\%) \MSun for Proxima
Centauri acting as a lens. This is the first and the only currently possible
measurement of the gravitational mass of Proxima Centauri.Comment: 10 pages, 6 figures, accepted by MNRA
The far-infrared/radio correlation for a sample of strongly lensed dusty star-forming galaxies detected by Herschel
We investigate the radio/far-infrared (FIR) correlation for a sample of 28 bright high-redshift (1 z 4) star-forming galaxies selected in the FIR from the Herschel -ATLAS fields as candidates to be strongly gravitationally lensed. The radio information comes either from high sensitivity dedicated Australia Telescope Compact Array observations at 2.1 GHz or from cross-matches with the FIRST surv e y at 1.4 GHz. By taking advantage of source brightness possibly enhanced by lensing magnification, we identify a weak evolution with redshift out to z 4 of the FIR-to-radio luminosity ratio q FIR . We also find that the q FIR parameter as a function of the radio power L 1 . 4 GHz displays a clear decreasing trend, similarly to what is observed for optically/radio- selected lensed quasars found in literature, yet co v ering a complementary region in the q FIR –L 1 . 4 GHz diagram. We interpret such a behaviour in the framework of an in situ galaxy formation scenario, as a result of the transition from an early dust-obscured star-forming phase (mainly pinpointed by our FIR selection) to a late radio-loud quasar phase (preferentially sampled by the optical/radio selection)
A panchromatic spatially-resolved analysis of nearby galaxies -- I. Sub-kpc scale Main Sequence in grand-design spirals
We analyse the spatially resolved relation between stellar mass (M)
and star formation rate (SFR) in disk galaxies (i.e. the Main Sequence, MS).
The studied sample includes eight nearby face-on grand-design spirals, e.g. the
descendant of high-redshift, rotationally-supported star-forming galaxies. We
exploit photometric information over 23 bands, from the UV to the far-IR, from
the publicly available DustPedia database to build spatially resolved maps of
stellar mass and star formation rates on sub-galactic scales of 0.5-1.5 kpc, by
performing a spectral energy distribution fitting procedure that accounts for
both the observed and the obscured star formation processes, over a wide range
of internal galaxy environments (bulges, spiral arms, outskirts). With more
than 30 thousands physical cells, we have derived a definition of the local
spatially resolved MS per unit area for disks,
=0.82log-8.69. This is consistent with the
bulk of recent results based on optical IFU, using the H line emission
as a SFR tracer. Our work extends the analysis at lower sensitivities in both
M and SFR surface densities, up to a factor 10. The self
consistency of the MS relation over different spatial scales, from sub-galactic
to galactic, as well as with a rescaled correlation obtained for high redshift
galaxies, clearly proves its universality.Comment: 21 pages, 15 figures. Accepted for publication in MNRA
A titanic interstellar medium ejection from a massive starburst galaxy at redshift 1.4
Feedback-driven winds from star formation or active galactic nuclei might be a relevant channel for the abrupt quenching of star formation in massive galaxies. However, both observations and simulations support the idea that these processes are non-conflictingly co-evolving and self-regulating. Furthermore, evidence of disruptive events that are capable of fast quenching is rare, and constraints on their statistical prevalence are lacking. Here we present a massive starburst galaxy at redshift z = 1.4, which is ejecting 46 ± 13% of its molecular gas mass at a startling rate of ≳10,000 M⊙ yr−1. A broad component that is red-shifted from the galaxy emission is detected in four (low and high J) CO and [C i] transitions and in the ionized phase, which ensures a robust estimate of the expelled gas mass. The implied statistics suggest that similar events are potentially a major star-formation quenching channel. However, our observations provide compelling evidence that this is not a feedback-driven wind, but rather material from a merger that has been probably tidally ejected. This finding challenges some literature studies in which the role of feedback-driven winds might be overstated
A panchromatic spatially resolved analysis of nearby galaxies-II. The main sequence-gas relation at sub-kpc scale in grand-design spirals
In this work, we analyse the connection between gas availability and the position of a region with respect to the spatially resolved main-sequence (MS) relation. Following the procedure presented in Enia et al. (2020), for a sample of five face-on, grand design spiral galaxies located on the MS we obtain estimates of stellar mass and star formation rate surface densities (E∗ and ESFR) within cells of 500 pc size. Thanks to HI 21cm and 12CO(2-1) maps of comparable resolution, within the same cells we estimate the surface densities of the atomic (EHI) and molecular (EH2) gas and explore the correlations among all these quantities. E∗, ESFR, and EH2 define a 3D relation whose projections are the spatially resolved MS, the Kennicutt-Schmidt law and the molecular gas MS. We find that EH2 steadily increases along the MS relation and is almost constant perpendicular to it. EHI is nearly constant along the MS and increases in its upper envelope. As a result, ESFR can be expressed as a function of E∗ and E HI, following the relation log ESFR = 0.97log E∗ + 1.99log EH I-11.11. We show that the total gas fraction significantly increases towards the starburst regions, accompanied by a weak increase in star formation efficiency. Finally, we find that H2/HI varies strongly with the distance from the MS, dropping dramatically in regions of intense star formation, where the UV radiation from newly formed stars dissociates the H2 molecule, illustrating the self-regulating nature of the star formation process
ALPINE−ALMA [C II] Survey: on the nature of an extremely obscured serendipitous galaxy
We report the serendipitous discovery of a dust-obscured galaxy observed as part of the Atacama Large Millimeter Array (ALMA) Large Program to INvestigate [C II] at Early times (ALPINE). While this galaxy is detected both in line and continuum emissions in ALMA Band 7, it is completely dark in the observed optical/near-infrared bands and only shows a significant detection in the UltraVISTA K_s band. We discuss the nature of the observed ALMA line, that is [C II] at z ∼ 4.6 or high-J CO transitions at z ∼ 2.2. In the first case, we find a [C II]/FIR luminosity ratio of log(L_([CII])/L_(FIR))∼−2.5, consistent with the average value for local star-forming galaxies (SFGs). In the second case instead, the source would lie at larger CO luminosities than those expected for local SFGs and high-z submillimetre galaxies. At both redshifts, we derive the star formation rate (SFR) from the ALMA continuum and the physical parameters of the galaxy, such as the stellar mass (M*), by fitting its spectral energy distribution. Exploiting the results of this work, we believe that our source is a ‘main-sequence’, dusty SFG at z = 4.6 (i.e. [C II] emitter) with log(SFR/M_⊙ yr⁻¹) ∼ 1.4 and log(M*/M_⊙) ∼ 9.9. As a support to this scenario our galaxy, if at this redshift, lies in a massive protocluster recently discovered at z ∼ 4.57, at only ∼1 proper Mpc from its centre. This work underlines the crucial role of the ALPINE survey in making a census of this class of objects, in order to unveil their contribution to the global SFR density at the end of the Reionization epoch
The ALPINE-ALMA [CII] Survey: On the nature of an extremely obscured serendipitous galaxy
We report the serendipitous discovery of a bright galaxy (Gal-A) observed as
part of the ALMA Large Program to INvestigate [CII] at Early times (ALPINE).
While this galaxy is detected both in line and continuum emission in ALMA Band
7, it is completely dark in UV/optical filters and only presents a marginal
detection in the UltraVISTA Ks band. We discuss the nature of the observed ALMA
line, i.e. whether the emission comes from [CII] at z~4.6, or from high-J CO
transitions at z~2.2. In the first case we find a [CII]-to-FIR luminosity ratio
of log(L_[CII]/L_FIR)=-2.5, consistent with the average value for local
star-forming galaxies (SFGs); in the second case, instead, the source would lie
outside of the empirical relations between L_CO and L_FIR found in the
literature. At both redshifts, we derive the star-formation rate (SFR) from the
ALMA continuum, and the stellar mass (M*) by using stellar population synthesis
models as input for LePHARE spectral energy distribution (SED) fitting.
Exploiting our results, we believe that Gal-A is a Main-Sequence (MS), dusty
SFG at z=4.6 (i.e. [CII] emitter) with log(SFR/[M/yr])~1.4 and log(M*/M)~9.7.
This work underlines the crucial role of the ALPINE survey in making a census
of this class of objects, in order to unveil their contribution to the global
star-formation rate density (SFRD) of the Universe at the end of the
Reionisation epoch.Comment: 13 pages, 6 figures. Submitted to MNRA
Icodextrin does not impact infectious and culture-negative peritonitis rates in peritoneal dialysis patients: a 2-year multicentre, comparative, prospective cohort study
Background. Icodextrin is a glucose polymer derived by hydrolysis of cornstarch. The different biocompatibility profile of icodextrin-containing peritoneal dialysis (PD) solutions may have a positive influence on peritoneal host defence. Furthermore, cases of sterile peritonitis potentially associated with icodextrin have been reported
Nutrition Risk Classification: A Reproducible and Valid Tool for Nurses
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141661/1/ncp0020.pd
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