47 research outputs found
The evolution of the equivalent width of the Hα emission line and specific star formation rate in star-forming galaxies at 1 < z < 5
We present the results of a study which uses spectral energy distribution
(SED) fitting to investigate the evolution of the equivalent width (EW) of the
Halpha emission line in star-forming galaxies over the redshift interval 1<z<5.
After first demonstrating the ability of our SED-fitting technique to recover
EW(Ha) using a sample of galaxies at z~1.3 with EW(Ha) measurements from 3D-HST
grism spectroscopy, we proceed to apply our technique to samples of
spectroscopically confirmed and photometric-redshift selected star-forming
galaxies at z>=1 in the CANDELS UDS and GOODS-S fields. Confining our analysis
to a constant stellar mass range (9.5<log(M/Msun)<10.5), we find that the
median EW(Ha) evolves only modestly with redshift, reaching a rest-frame value
of EW(Ha)=301+/-30 Angs by redshift z~4.5. Furthermore, using estimates of
star-formation rate (SFR) based on both UV luminosity and Ha line flux, we use
our galaxy samples to compare the evolution of EW(Ha) and specific
star-formation rate (sSFR). Our results indicate that over the redshift range
1<z<5, the evolution displayed by EW(Ha) and sSFR is consistent, and can be
adequately parameterized as: propto (1+z)^(1.0+/-0.2). As a consequence, over
this redshift range we find that the sSFR and rest-frame EW(Ha) of star-forming
galaxies with stellar masses M~10^(10) Msun are related by:
EW(Ha)/Ang=(63+/-7)sSFR/Gyr^(-1). Given the current uncertainties in measuring
the SFRs of high-redshift galaxies, we conclude that EW(Ha) provides a useful
independent tracer of sSFR for star-forming galaxies out to redshifts of z=5.Comment: Version accepted to publication in MNRAS, 11 pages, 5 figures, 1
tabl
The effects of spatial resolution on Integral Field Spectrograph surveys at different redshifts. The CALIFA perspective
Over the past decade, 3D optical spectroscopy has become the preferred tool
for understanding the properties of galaxies and is now increasingly used to
carry out galaxy surveys. Low redshift surveys include SAURON, DiskMass,
ATLAS3D, PINGS and VENGA. At redshifts above 0.7, surveys such as MASSIV, SINS,
GLACE, and IMAGES have targeted the most luminous galaxies to study mainly
their kinematic properties. The on-going CALIFA survey () is the
first of a series of upcoming Integral Field Spectroscopy (IFS) surveys with
large samples representative of the entire population of galaxies. Others
include SAMI and MaNGA at lower redshift and the upcoming KMOS surveys at
higher redshift. Given the importance of spatial scales in IFS surveys, the
study of the effects of spatial resolution on the recovered parameters becomes
important. We explore the capability of the CALIFA survey and a hypothetical
higher redshift survey to reproduce the properties of a sample of objects
observed with better spatial resolution at lower redshift. Using a sample of
PINGS galaxies, we simulate observations at different redshifts. We then study
the behaviour of different parameters as the spatial resolution degrades with
increasing redshift.Comment: 20 pages, 16 figures. Accepted for publication in A&
CALIFA, the Calar Alto Legacy Integral Field Area survey: I. Survey presentation
We present here the Calar Alto Legacy Integral Field Area (CALIFA) survey,
which has been designed to provide a first step in this direction.We summarize
the survey goals and design, including sample selection and observational
strategy.We also showcase the data taken during the first observing runs
(June/July 2010) and outline the reduction pipeline, quality control schemes
and general characteristics of the reduced data. This survey is obtaining
spatially resolved spectroscopic information of a diameter selected sample of
galaxies in the Local Universe (0.005< z <0.03). CALIFA has been
designed to allow the building of two-dimensional maps of the following
quantities: (a) stellar populations: ages and metallicities; (b) ionized gas:
distribution, excitation mechanism and chemical abundances; and (c) kinematic
properties: both from stellar and ionized gas components. CALIFA uses the PPAK
Integral Field Unit (IFU), with a hexagonal field-of-view of
\sim1.3\sq\arcmin', with a 100% covering factor by adopting a three-pointing
dithering scheme. The optical wavelength range is covered from 3700 to 7000
{\AA}, using two overlapping setups (V500 and V1200), with different
resolutions: R\sim850 and R\sim1650, respectively. CALIFA is a legacy survey,
intended for the community. The reduced data will be released, once the quality
has been guaranteed. The analyzed data fulfill the expectations of the original
observing proposal, on the basis of a set of quality checks and exploratory
analysis.
We conclude from this first look at the data that CALIFA will be an important
resource for archaeological studies of galaxies in the Local Universe.Comment: 32 pages, 29 figures, Accepted for publishing in Astronomy and
Astrophysic
Gold as a Tool for Hedging Financial Risks
The article discusses gold as a protective asset, which claims to be a high-efficiency tool for hedging financial risks. In the introductory part the general characteristics of hedging as a method of full or partial risk elimination is given, and the main known types of risk hedging typical for a financial asset portfolio holder are considered. Further, dynamics of the world prices for gold is analyzed in a historical retrospective, whereby the conclusion is drawn on a tendency of this asset to grow during the periods of financial instability, and also if new financial assets appear. In the final part of the article the assessment of gold as a tool for hedging financial risks is given
A comparison of surgical devices for grade II and III hemorrhoidal disease. Results from the LigaLongo Trial comparing transanal Doppler-guided hemorrhoidal artery ligation with mucopexy and circular stapled hemorrhoidopexy
PURPOSE: Little is presently known on the impact of device type for Doppler-guided hemorrhoidal artery ligation/mucopexy (DGHAL) or circular stapled hemorrhoidopexy (CSH) when a surgical treatment is considered for hemorrhoidal disease (HD). In this study, we aimed to compare the outcome in terms of adverse events and recurrence rate, of patients included in the multicenter LigaLongo RCT ( ClinicalTrials.gov NCT01240772) according to the type of devices used.
METHODS: In the DGHAL arm (N = 193), the procedure was done with transanal hemorrhoidal dearterialization (THD)™ (THD, Correggio, Italy) (104 patients) and with HAL-RAR™ (Agency for Medical Innovations (AMI) GmbH, Feldkirch, Austria) (89 patients). In the CSH arm (N = 184), procedure for prolapse and hemorrhoids (PPH)-03™ (Ethicon Endo-Surgery, Cincinnati OH) and hemorrhoidopexy and prolapse (HEM)™ (Covidien, Inc.) staplers were used in respectively 106 and 78 cases. Surgery-related morbidity at 90 postoperative days (POD) based on the Clavien-Dindo procedure-related complication score and clinical outcome in terms of recurrence and reoperation rate at 12 postoperative months (POM) was collected.
RESULTS: Three hundred and seventy-seven patients were randomized according to HD grade. In the DGHAL arm, the number of ligations and mucopexies was higher in the AMI group (p < 0.0001); at 90 POD, the overall morbidity was similar between the two groups. In the CSH arm, donut sizes were similar; at 90 POD, the PPH group had a higher risk of postoperative grade 1 morbidity (anal urgency or incontinence) compared to the HEM group (p = 0.003). At 12 POM, no statistical difference was found between the two groups of each arm in terms of grade III recurrence or reoperation.
CONCLUSION: Postoperative morbidity and outcome at 1 year were similar regardless of the type of devices used. These findings suggest that device type has little impact on HD treatment results.
TRIAL REGISTRATION: clinicaltrials.gov -Identifier NCT01240772
On the Faint End of the Galaxy Luminosity Function in the Epoch of Reionization: Updated Constraints from the HST Frontier Fields
Ultra-faint galaxies are hosted by small dark matter halos with shallow gravitational potential wells, hence their star formation activity is more sensitive to feedback effects. The shape of the faint end of the high-z galaxy luminosity function (LF) contains important information on star formation and its interaction with the reionization process during the Epoch of Reionization. High-z galaxies with {M}UV}≳ -17 have only recently become accessible thanks to the Frontier Fields (FFs) survey combining deep HST imaging and the gravitational lensing effect. In this paper we investigate the faint end of the LF at redshift >5 using the data of FFs clusters Abell 2744 (A2744), MACSJ0416.1-2403 (M0416), MACSJ0717.5+3745 (M0717), and MACSJ1149.5+2223 (M1149). We analyze both an empirical and a physically motivated LF model to obtain constraints on a possible turnover of LF at faint magnitudes. In the empirical model the LF drops fast when the absolute UV magnitude {M}UV} is much larger than a turnover absolute UV magnitude {M}UV}{{T}}. We obtain {M}UV}{{T}}≳ -14.6 (15.2) at the 1 (2)σ confidence level (C.L.) for z ∼ 6. In the physically motivated analytical model, star formation in halos with circular velocity below {v}c* is fully quenched if these halos are located in ionized regions. Using updated lensing models and new additional FFs data, we re-analyze previous constraints on {v}c* and f esc presented by Castellano et al. using a smaller data set. We obtain new constraints on {v}c* ≲ 59 km s-1 and f esc ≲ 56% (both at 2σ C.L.) and conclude that there is no turnover detected so far from the analyzed FFs data. Forthcoming JWST observations will be key to tightening these constraints further
The VANDELS ESO public spectroscopic survey: Observations and first data release
This paper describes the observations and the first data release (DR1) of the ESO public spectroscopic survey “VANDELS, a deep VIMOS survey of the CANDELS CDFS and UDS fields”. The main targets of VANDELS are star-forming galaxies at redshift 2.4 < z < 5.5, an epoch when the Universe had not yet reached 20% of its current age, and massive passive galaxies in the range 1 < z < 2.5. By adopting a strategy of ultra-long exposure times, ranging from a minimum of 20 h to a maximum of 80 h per source, VANDELS is specifically designed to be the deepest-ever spectroscopic survey of the high-redshift Universe. Exploiting the red sensitivity of the refurbished VIMOS spectrograph, the survey is obtaining ultra-deep optical spectroscopy covering the wavelength range 4800–10 000 Å with a sufficiently high signal-to-noise ratio to investigate the astrophysics of high-redshift galaxy evolution via detailed absorption line studies of well-defined samples of high-redshift galaxies. VANDELS-DR1 is the release of all medium-resolution spectroscopic data obtained during the first season of observations, on a 0.2 square degree area centered around the CANDELS-CDFS (Chandra deep-field south) and CANDELS-UDS (ultra-deep survey) areas. It includes data for all galaxies for which the total (or half of the total) scheduled integration time was completed. The DR1 contains 879 individual objects, approximately half in each of the two fields, that have a measured redshift, with the highest reliable redshifts reaching zspec ~ 6. In DR1 we include fully wavelength-calibrated and flux-calibrated 1D spectra, the associated error spectrum and sky spectrum, and the associated wavelength-calibrated 2D spectra. We also provide a catalog with the essential galaxy parameters, including spectroscopic redshifts and redshift quality flags measured by the collaboration. We present the survey layout and observations, the data reduction and redshift measurement procedure, and the general properties of the VANDELS-DR1 sample. In particular, we discuss the spectroscopic redshift distribution and the accuracy of the photometricredshifts for each individual target category, and we provide some examples of data products for the various target typesand the different quality flags. All VANDELS-DR1 data are publicly available and can be retrieved from the ESO archive. Two further data releases are foreseen in the next two years, and a final data release is currently scheduled for June 2020, which will include an improved rereduction of the entire spectroscopic data set