The
Planck
satellite has identified more than 2000 protocluster candidates with extreme star formation rates (SFRs). Here, we present the spectroscopic identification of a
Planck
-selected ...protocluster located in the Cosmos field, PHz G237.01+42.50. PHz G237.01+42.50 contains a galaxy overdensity of 31 spectroscopically identified galaxies at
z
≃ 2.16 (significant at 5.4
σ
) in a 10′ × 11′ region. The overdensity contains two substructures or protoclusters at ⟨
z
⟩ ≃ 2.16 and 2.195 with estimated halo masses at
z
= 0 of ∼5–6 × 10
14
M
⊙
, roughly consistent with Virgo-type clusters. The overdensity total SFR, ∼4000
M
⊙
yr
−1
, is higher than predicted by simulations but much smaller than the SFR derived from the
Planck
data (i.e., 10 173
M
⊙
yr
−1
). The analysis of the
Herschel
data in the field, in combination with the available ancillary data, shows that such a difference is due to an effect of source alignment along the line of sight that produces a 5
σ
overdensity of red
Herschel
sources in the field. We analyze the members’ ultraviolet (UV) spectra and UV-far-infrared spectral energy distributions to derive their SFR, stellar mass, and metallicity. Galaxy members include blue star-forming galaxies and Active galactic nuclei (AGN) with SFRs and stellar masses consistent with the main sequence. Active galactic nuclei, identified through optical spectroscopy or X-ray data, represent a significant fraction (20 ± 10%) of all members of the protocluster at
z
= 2.16, and they are powerful enough to produce radiative feedback. The core of this protocluster, besides being denser, includes members that are, on average, more massive and star-forming and contains a larger fraction of AGN and
Herschel
-detected galaxies than the full sample, suggesting an environmental effect on galaxy growth. A comparison between PHz G237.01+42.50 and other protoclusters in the literature at similar redshifts reveals some common traits and differences that reflect both observational biases and a diversity in intrinsic properties that is not yet fully understood.
GJ3470b is a rare example of a “hot Uranus” transiting exoplanet orbiting a nearby M1.5 dwarf. It is crucial for atmospheric studies because it is one of the most inflated low-mass planets known, ...bridging the boundary between “super-Earths” and Neptunian planets. We present two new ground-based light curves of GJ3470b gathered by the LBC camera at the Large Binocular Telescope. Simultaneous photometry in the ultraviolet (λc = 357.5 nm) and optical infrared (λc = 963.5 nm) allowed us to detect a significant change in the effective radius of GJ3470b as a function of wavelength. This can be interpreted as a signature of scattering processes occurring in the planetary atmosphere, which should be cloud-free and with a low mean molecular weight. The unprecedented accuracy of our measurements demonstrates that the photometric detection of Earth-sized planets around M dwarfs is achievable using 8−10 m size ground-based telescopes. We provide updated planetary parameters and a greatly improved orbital ephemeris for any forthcoming study of this planet.
EZ: A Tool For Automatic Redshift Measurement Garilli, B.; Fumana, M.; Franzetti, P. ...
Publications of the Astronomical Society of the Pacific,
07/2010, Letnik:
122, Številka:
893
Journal Article
Recenzirano
Odprti dostop
We present EZ (Easy redshift), a tool we have developed within the VVDS project to help in redshift measurement from optical spectra. EZ has been designed with large spectroscopic surveys in mind, ...and in its development particular care has been given to the reliability of the results obtained in an automatic and unsupervised mode. Nevertheless, the possibility of running it interactively has been preserved, and a graphical user interface for results inspection has been designed. EZ has been successfully used within the VVDS project, as well as the zCosmos one. In this article we describe its architecture and the algorithms used, and evaluate its performances both on simulated and real data. EZ is an open-source program, freely downloadable from the Pandora Web Site.1
ABSTRACT
We present sipgi, a spectroscopic pipeline to reduce optical/near-infrared data from slit-based spectrographs. sipgi is a complete spectroscopic data reduction environment, which retains the ...high level of flexibility and accuracy typical of the standard ‘by-hand’ reduction methods but is characterized by a significantly higher level of efficiency. This is obtained by exploiting three main concepts: (i) the instrument model: at the core of the data reduction is an analytic description of the main calibration relations (e.g. spectra location and wavelength calibration) that can be easily checked and adjusted on data using a graphical tool; (ii) a built-in data organizer that classifies the data, together with a graphical interface that helps in providing the recipes with the correct input; (iii) the design and flexibility of the reduction recipes: The number of tasks required to perform a complete reduction is minimized, while preserving the possibility of verifying the accuracy of the main stages of data-reduction process with provided tools. The current version of sipgi manages data from the MODS and LUCI spectrographs mounted at the Large Binocular Telescope, and it is our plan to extend sipgi to support other through-slit spectrographs. Meanwhile, to allow using the same approach based on the instrument model with other instruments, we have developed SpectraPy, a spectrograph-independent python library working on through-slit spectra. In its current version, SpectraPy produces two-dimensional wavelength-calibrated spectra corrected by instrument distortions. The current release of sipgi and its documentation can be downloaded fromhttp://pandora.lambrate.inaf.it/sipgi/, while SpectraPy can be found at http://pandora.lambrate.inaf.it/SpectraPy/.
ABSTRACT We present Easylife, the software environment developed within the framework of the VIPERS project for automatic data reduction and survey handling. Easylife is a comprehensive system to ...automatically reduce spectroscopic data, to monitor the survey advancement at all stages, to distribute data within the collaboration, and to release data to the whole community. It is based on the OPTICON-founded project FASE, and inherits the FASE capabilities of modularity and scalability. After describing the software architecture, the main reduction and quality control features, and the main services made available, we show its performance in terms of reliability of results. We also show how it can be ported to other projects with different characteristics.
We present deep 3500-10000 spectra of H ii regions and planetary nebulae (PNe) in the starburst irregular galaxy NGC 4449, acquired with the Multi Object Double Spectrograph at the Large Binocular ...Telescope. Using the "direct" method, we derived the abundance of He, N, O, Ne, Ar, and S in six H ii regions and in four PNe in NGC 4449. This is the first case of PNe studied in a starburst irregular outside the Local Group. Our H ii region and PN sample extends over a galactocentric distance range of 2 kpc and spans 0.2 dex in oxygen abundance, with average values of and 8.3 0.1 for H ii regions and PNe, respectively. PNe and H ii regions exhibit similar oxygen abundances in the galactocentric distance range of overlap, while PNe appear more than ∼1 dex enhanced in nitrogen with respect to H ii regions. The latter result is the natural consequence of N being mostly synthesized in intermediate-mass stars and brought to the stellar surface during dredge-up episodes. On the other hand, the similarity in O abundance between H ii regions and PNe suggests that NGC 4449's interstellar medium has been poorly enriched in -elements since the progenitors of the PNe were formed. Finally, our data reveal the presence of a negative oxygen gradient for both H ii regions and PNe, while nitrogen does not exhibit any significant radial trend. We ascribe the (unexpected) nitrogen behavior to local N enrichment by the conspicuous Wolf-Rayet population in NGC 4449.
Context.
Stage IV weak lensing experiments will offer more than an order of magnitude leap in precision. We must therefore ensure that our analyses remain accurate in this new era. Accordingly, ...previously ignored systematic effects must be addressed.
Aims.
In this work, we evaluate the impact of the reduced shear approximation and magnification bias on information obtained from the angular power spectrum. To first-order, the statistics of reduced shear, a combination of shear and convergence, are taken to be equal to those of shear. However, this approximation can induce a bias in the cosmological parameters that can no longer be neglected. A separate bias arises from the statistics of shear being altered by the preferential selection of galaxies and the dilution of their surface densities in high-magnification regions.
Methods.
The corrections for these systematic effects take similar forms, allowing them to be treated together. We calculated the impact of neglecting these effects on the cosmological parameters that would be determined from
Euclid
, using cosmic shear tomography. To do so, we employed the Fisher matrix formalism, and included the impact of the super-sample covariance. We also demonstrate how the reduced shear correction can be calculated using a lognormal field forward modelling approach.
Results.
These effects cause significant biases in Ω
m
,
σ
8
,
n
s
, Ω
DE
,
w
0
, and
w
a
of −0.53
σ
, 0.43
σ
, −0.34
σ
, 1.36
σ
, −0.68
σ
, and 1.21
σ
, respectively. We then show that these lensing biases interact with another systematic effect: the intrinsic alignment of galaxies. Accordingly, we have developed the formalism for an intrinsic alignment-enhanced lensing bias correction. Applying this to
Euclid
, we find that the additional terms introduced by this correction are sub-dominant.
Weak lensing, which is the deflection of light by matter along the line of sight, has proven to be an efficient method for constraining models of structure formation and reveal the nature of dark ...energy. So far, most weak-lensing studies have focused on the shear field that can be measured directly from the ellipticity of background galaxies. However, within the context of forthcoming full-sky weak-lensing surveys such as
Euclid
, convergence maps (mass maps) offer an important advantage over shear fields in terms of cosmological exploitation. While it carry the same information, the lensing signal is more compressed in the convergence maps than in the shear field. This simplifies otherwise computationally expensive analyses, for instance, non-Gaussianity studies. However, the inversion of the non-local shear field requires accurate control of systematic effects caused by holes in the data field, field borders, shape noise, and the fact that the shear is not a direct observable (reduced shear). We present the two mass-inversion methods that are included in the official
Euclid
data-processing pipeline: the standard Kaiser & Squires method (KS), and a new mass-inversion method (KS+) that aims to reduce the information loss during the mass inversion. This new method is based on the KS method and includes corrections for mass-mapping systematic effects. The results of the KS+ method are compared to the original implementation of the KS method in its simplest form, using the
Euclid
Flagship mock galaxy catalogue. In particular, we estimate the quality of the reconstruction by comparing the two-point correlation functions and third- and fourth-order moments obtained from shear and convergence maps, and we analyse each systematic effect independently and simultaneously. We show that the KS+ method substantially reduces the errors on the two-point correlation function and moments compared to the KS method. In particular, we show that the errors introduced by the mass inversion on the two-point correlation of the convergence maps are reduced by a factor of about 5, while the errors on the third- and fourth-order moments are reduced by factors of about 2 and 10, respectively.
Abstract
We present intermediate-resolution (R ∼ 1000) spectra in the ∼3500–10 000 Å range of 14 globular clusters in the Magellanic irregular galaxy NGC 4449 acquired with the Multi-Object Double ...Spectrograph on the Large Binocular Telescope. We derived Lick indices in the optical and the Ca ii triplet index in the near-infrared in order to infer the clusters’ stellar population properties. The inferred cluster ages are typically older than ∼9 Gyr, although ages are derived with large uncertainties. The clusters exhibit intermediate metallicities, in the range −1.2 ≲ Fe/H ≲ −0.7, and typically sub-solar α/Fe ratios, with a peak at ∼−0.4. These properties suggest that (i) during the first few Gyr NGC 4449 formed stars slowly and inefficiently, with galactic winds having possibly contributed to the expulsion of the α-elements, and (ii) globular clusters in NGC 4449 formed relatively ‘late’, from a medium already enriched in the products of Type Ia supernovae. The majority of clusters appear also underabundant in CN compared to Milky Way halo globular clusters, perhaps because of the lack of a conspicuous N-enriched, second generation of stars like that observed in Galactic globular clusters. Using the cluster velocities, we infer the dynamical mass of NGC 4449 inside 2.88 kpc to be M(<2.88 kpc) = $3.15^{+3.16}_{-0.75} \times 10^9\,{\rm M}_{\odot }$. We also report the serendipitous discovery of a planetary nebula within one of the targeted clusters, a rather rare event.
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