84 research outputs found
On the Anticorrelation Between Galaxy Light Concentration and X-ray-to-Optical Flux Ratio
Active Galactic Nuclei (AGN) play an important role in many aspects of the
modern cosmology, and of particular interest is the issue of the interplay
between AGN and their host galaxy. Using X-ray and optical data sets, we have
explored the properties of a large sample of AGNs in the Subaru/XMM-Newton Deep
Survey (SXDS) field, and studied their evolution in relation with the evolution
of their host galaxy. We present here an anticorrelation between
X-ray-to-optical flux ratio (X/O) and galaxy light concentration (C), which has
been found for the first time and might suggest that early type galaxies,
having poor matter supply to feed the AGN activity, have lower Eddington rates
than those of late type galaxies.Comment: 9 pages, 3 figures, accepted for publication in ApJ Letter
OTELO survey: optimal emission-line flux determination with OSIRIS/GTC
Emission-line galaxies are important targets for understanding the chemical
evolution of galaxies in the universe. Deep, narrow-band imaging surveys allow
to detect and study the flux and the equivalent widths (EW) of the emission
line studied. The present work has been developed within the context of the
OTELO project, an emission line survey using the Tunable Filters (TF) of
OSIRIS, the first generation instrument on the GTC 10.4m telescope located in
La Palma, Spain, that will observe through selected atmospheric windows
relatively free of sky emission lines. With a total survey area of 0.1 square
degrees distributed in different fields, reaching a 5 \sigma depth of 10^-18
erg/cm^2/s and detecting objects of EW < 0.3 A, OTELO will be the deepest
emission line survey to date. As part of the OTELO preparatory activities, the
objective of this study is to determine the best combination of sampling and
full width at half maximum (FWHM) for the OSIRIS tunable filters for deblending
H\alpha from [NII] lines by analyzing the flux errors obtained. We simulated
the OTELO data by convolving a complete set of synthetic HII galaxies in EW
with different widths of the OSIRIS TFs. We estimated relative flux errors of
the recovered H\alpha and [NII]6583 lines. We found that, for the red TF, a
FWHM of 12 A and a sampling of 5 A is an optimal combination that allow
deblending H\alpha from the [NII]6583 line with a flux error lower than 20%.
This combination will allow estimating SFRs and metallicities using the H\alpha
flux and the N2 method, respectively.Comment: 16 pages, 9 figures. Some authors added. Accepted for publication in
PAS
The nuclear and extended infrared emission of the Seyfert galaxy NGC 2992 and the interacting system Arp 245
We present subarcsecond resolution infrared (IR) imaging and mid-IR
spectroscopic observations of the Seyfert 1.9 galaxy NGC 2992, obtained with
the Gemini North Telescope and the Gran Telescopio CANARIAS (GTC). The N-band
image reveals faint extended emission out to ~3 kpc, and the PAH features
detected in the GTC/CanariCam 7.5-13 micron spectrum indicate that the bulk of
this extended emission is dust heated by star formation. We also report
arcsecond resolution MIR and far-IR imaging of the interacting system Arp 245,
taken with the Spitzer Space Telescope and the Herschel Space Observatory.
Using these data, we obtain nuclear fluxes using different methods and find
that we can only recover the nuclear fluxes obtained from the subarcsecond data
at 20-25 micron, where the AGN emission dominates. We fitted the nuclear IR
spectral energy distribution of NGC 2992, including the GTC/CanariCam nuclear
spectrum (~50 pc), with clumpy torus models. We then used the best-fitting
torus model to decompose the Spitzer/IRS 5-30 spectrum (~630 pc) in AGN and
starburst components, using different starburst templates. We find that,
whereas at shorter mid-IR wavelengths the starburst component dominates (64% at
6 micron), the AGN component reaches 90% at 20 micron. We finally obtained dust
masses, temperatures and star formation rates for the different components of
the Arp 245 system and find similar values for NGC 2992 and NGC 2993. These
measurements are within those reported for other interacting systems in the
first stages of the interaction.Comment: 20 pages, 12 figures, accepted by MNRA
Variable broad lines and outflow in the weak blazar PBC J2333.9-2343
Indexación: Scopus; Scielo.Funding text #1
1Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Gran Bretaña 1111, Playa Ancha, Valparaíso, Chile 2INAF – Istituto di Astrofisica e Planetologia Spaziali di Roma (IAPS-INAF), Via del Fosso del Cavaliere 100, I-00133 Roma, Italy 3INAF – Osservatorio Astronomico di Roma, via Frascati 33, I-00078 Monte Porzio Catone, Italy 4Excellence Cluster Universe, Technische Universität München, Boltzmannstr. 2, D-85748, Garching, Germany 5European Southern Observatory, Karl-Schwarzschild-Str 2, D-85748 Garching b. München, Germany 6Instituto Nacional de Astrofísica, Óptica y Electrónica, Apartado Postal 51-216, 72000 Puebla, México 7Argelander Institute for Astronomy, University of Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany 8International Max Planck Research School of Astronomy and Astrophysics at the Universities of Bonn and Cologne, Auf dem Hügel 69, D-53121 Bonn, Germany 9INAF – Osservatorio di Astrofisica e Scienza dello Spazio, via Gobetti 93/3, I-40129 Bo...View all
Funding text #2
We acknowledge the referee, M. Villar Martín, for her comments and suggestions that helped to improve the paper. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester, the NASA/IPAC extragalactic database (NED), the STARLIGHT code, and the IRAF software. Based upon observations carried out at the Observatorio Astronómico Nacional on the Sierra San Pedro Mártir (OAN-SPM), Baja California, México. LHG and FP acknowledge the ASI/INAF agreement number 2013-023-R1, LHG partial support from FONDECYT through grant 3170527, MP from ESSTI under the MoST, and from MINECO through research projects AYA2013-42227-P and AYA2016-76682-C3-1-P (AEI/FEDER, UE), LHG and SC from the Spanish grant AYA2013-42227-P, VC by CONACyT research grant 280789, EFJA from the Collaborative Research Center 956, subproject A1, funded by DFG, and GV from the DFG Cluster of Excellence ‘Origin and Structure of the Universe’ (www.universe-cluster.de).PBC J2333.9-2343 is a peculiar active nucleus with two giant radio lobes and a weak blazarlike nucleus at their centre. In this work we show new optical, ultraviolet (UV), and X-ray data taken from the San Pedro Mártir telescope, the New Technology Telescope, NTT/EFOSC2, and the Swift/XRT satellite. The source is highly variable at all frequencies, in particular the strongest variations are found in the broad Hα component with a flux increase of 61±4 per cent between 2009 and 2016, following the X-ray flux increase of 62±6 per cent between 2010 and 2016. We also detected a broad Hβ component in 2016, making the optical classification change from type 1.9 to type 1.8 in 1 yr. We have also detected a broad component of the [OIII]λ5007 line, which is blue-shifted and of high velocity, suggesting an origin from a highly disturbed medium, possibly an outflow. The line flux variability and broad widths are indicative of a jet that is, at least in part, responsible for the ionization of the broad line region (BLR) and narrow line region (NLR). © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.https://academic.oup.com/mnras/article-abstract/478/4/4634/4999938?redirectedFrom=fulltex
AGN-Host Galaxy Connection: Morphology and Colours of X-ray Selected AGN at z < 2
The connection between AGN and their host galaxies has been widely studied
over recent years, showing it to be of great importance for providing answers
to some fundamental questions related with AGN fueling mechanisms, their
formation and evolution. Using X-ray and one of the deepest broad-band optical
data sets, we studied morphology and colours in relationship with X-ray
properties for sources at redshifts z < 2.0, using a sample of 262 AGN in the
Subaru/XMM-Newton Deep Survey (SXDS). Morphological classification was obtained
using the galSVM code, one of the new methods useful especially when dealing
with high-redshift sources and low-resolution data. Colour-magnitude diagrams
were studied in relationship with redshift, morphology, X-ray obscuration, and
X-ray-to-optical flux ratio. Finally, the significance of different regions was
analysed on colour-magnitude diagrams, relating the observed properties of AGN
populations with some models of their formation and evolution.Comment: 24 pages, 19 figures, accepted for publication in
Astronomy&Astrophysic
The ALHAMBRA Survey: Bayesian Photometric Redshifts with 23 bands for 3 squared degrees
The ALHAMBRA (Advance Large Homogeneous Area Medium Band Redshift
Astronomical) survey has observed 8 different regions of the sky, including
sections of the COSMOS, DEEP2, ELAIS, GOODS-N, SDSS and Groth fields using a
new photometric system with 20 contiguous ~ filters covering the
optical range, combining them with deep imaging. The observations,
carried out with the Calar Alto 3.5m telescope using the wide field (0.25 sq.
deg FOV) optical camera LAICA and the NIR instrument Omega-2000, correspond to
~700hrs on-target science images. The photometric system was designed to
maximize the effective depth of the survey in terms of accurate spectral-type
and photo-zs estimation along with the capability of identification of
relatively faint emission lines. Here we present multicolor photometry and
photo-zs for ~438k galaxies, detected in synthetic F814W images, complete down
to I~24.5 AB, taking into account realistic noise estimates, and correcting by
PSF and aperture effects with the ColorPro software. The photometric ZP have
been calibrated using stellar transformation equations and refined internally,
using a new technique based on the highly robust photometric redshifts measured
for emission line galaxies. We calculate photometric redshifts with the BPZ2
code, which includes new empirically calibrated templates and priors. Our
photo-zs have a precision of for I<22.5 and 1.4% for
22.5<I<24.5. Precisions of less than 0.5% are reached for the brighter
spectroscopic sample, showing the potential of medium-band photometric surveys.
The global shows a mean redshift =0.56 for I=0.86 for
I<24.5 AB. The data presented here covers an effective area of 2.79 sq. deg,
split into 14 strips of 58.5'x15.5' and represents ~32 hrs of on-target.Comment: The catalog data and a full resolution version of this paper is
available at https://cloud.iaa.csic.es/alhambra
A fundamental plane for field star-forming galaxies
Star formation rate (SFR), metallicity and stellar mass are within the
important parameters of star--forming galaxies that characterize their
formation and evolution. They are known to be related to each other at low and
high redshift in the mass--metallicity, mass--SFR, and metallicity--SFR
relations. In this work we demonstrate the existence of a plane in the 3D space
defined by the axes SFR [log(SFR)(M_sun yr^-1)], gas metallicity [12+log(O/H)],
and stellar mass [log(M_star/M_sun)] of star-forming galaxies. We used
star--forming galaxies from the "main galaxy sample" of the Sloan Digital Sky
Survey--Data Release 7 (SDSS-DR7) in the redshift range 0.04 < z < 0.1 and
r-magnitudes between 14.5 and 17.77. Metallicities, SFRs, and stellar masses
were taken from the Max-Planck-Institute for Astrophysics-John Hopkins
University (MPA-JHU) emission line analysis database. From a final sample of
44214 galaxies, we find for the first time a fundamental plane for field
galaxies relating the SFR, gas metallicity, and stellar mass for star--forming
galaxies in the local universe. One of the applications of this plane would be
estimating stellar masses from SFR and metallicity. High redshift data from the
literature at redshift ~2.2 and 3.5, do not show evidence for evolution in this
fundamental plane.Comment: Accepted for publication in A&A. 4 pages, 4 Figures, and 2 online
figure
Stellar populations of galaxies in the ALHAMBRA survey up to . II. Stellar content of quiescent galaxies within the dust-corrected stellar masscolour and the colourcolour diagrams
Our aim is to determine the distribution of stellar population parameters
(extinction, age, metallicity, and star formation rate) of quiescent galaxies
within the rest-frame stellar masscolour and colourcolour diagrams
corrected for extinction up to . These novel diagrams reduce the
contamination in samples of quiescent galaxies owing to dust-reddened galaxies,
and they provide useful constraints on stellar population parameters. We set
constraints on the stellar population parameters of quiescent galaxies
combining the ALHAMBRA multi-filter photo-spectra with our SED-fitting code
MUFFIT, making use of composite stellar population models. The extinction
obtained by MUFFIT allowed us to remove dusty star-forming (DSF) galaxies from
the sample of red galaxies. The distributions of stellar population
parameters across these rest-frame diagrams are revealed after the dust
correction and are fitted by the LOESS method to reduce uncertainty effects.
Quiescent galaxy samples defined via classical diagrams are typically
contaminated by a % fraction of DSF galaxies. A significant part of the
galaxies in the green valley are actually obscured star-forming galaxies
(%). Consequently, the transition of galaxies from the blue cloud to
the red sequence, and hence the related mechanisms for quenching, seems to be
much more efficient and faster than previously reported. The rest-frame stellar
masscolour and colourcolour diagrams are useful for constraining
the age, metallicity, extinction, and star formation rate of quiescent galaxies
by only their redshift, rest-frame colours, and/or stellar mass. Dust
correction plays an important role in understanding how quiescent galaxies are
distributed in these diagrams and is key to performing a pure selection of
quiescent galaxies via intrinsic colours.Comment: (37 pages, 29 figures, accepted for publication in A&A
High redshift galaxies in the ALHAMBRA survey: I. selection method and number counts based on redshift PDFs
Context. Most observational results on the high redshift restframe UV-bright
galaxies are based on samples pinpointed using the so called dropout technique
or Ly-alpha selection. However, the availability of multifilter data allows now
replacing the dropout selections by direct methods based on photometric
redshifts. In this paper we present the methodology to select and study the
population of high redshift galaxies in the ALHAMBRA survey data. Aims. Our aim
is to develop a less biased methodology than the traditional dropout technique
to study the high redshift galaxies in ALHAMBRA and other multifilter data.
Thanks to the wide area ALHAMBRA covers, we especially aim at contributing in
the study of the brightest, less frequent, high redshift galaxies. Methods. The
methodology is based on redshift probability distribution functions (zPDFs). It
is shown how a clean galaxy sample can be obtained by selecting the galaxies
with high integrated probability of being within a given redshift interval.
However, reaching both a complete and clean sample with this method is
challenging. Hence, a method to derive statistical properties by summing the
zPDFs of all the galaxies in the redshift bin of interest is introduced.
Results. Using this methodology we derive the galaxy rest frame UV number
counts in five redshift bins centred at z=2.5, 3.0, 3.5, 4.0, and 4.5, being
complete up to the limiting magnitude at m_UV(AB)=24. With the wide field
ALHAMBRA data we especially contribute in the study of the brightest ends of
these counts, sampling well the surface densities down to m_UV(AB)=21-22.
Conclusions. We show that using the zPDFs it is easy to select a clean sample
of high redshift galaxies. We also show that statistical analysis of the
properties of galaxies is better done using a probabilistic approach, which
takes into account both the incompleteness and contamination in a natural way.Comment: 16 pages, 11 figures; Accepted for A&A; language correcte
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