12,145 research outputs found
XMM-Newton and Deep Optical Observations of the OTELO fields: the Groth-Westphal Strip
OTELO (OSIRIS Tunable Emission Line Object Survey) will be carried out with
the OSIRIS instrument at the 10 m GTC telescope at La Palma, and is aimed to be
the deepest and richest survey of emission line objects to date. The deep
narrow-band optical data from OSIRIS will be complemented by means of
additional observations that include: (i) an exploratory broad-band survey that
is already being carried out in the optical domain, (ii) FIR and sub-mm
observations to be carried with the Herschel space telescope and the GTM, and
(iii) deep X-Ray observations from XMM-Newton and Chandra.Here we present a
preliminary analysis of public EPIC data of one of the OTELO targets,the
Groth-Westphal strip, gathered from the XMM-Newton Science Archive (XSA). EPIC
images are combined with optical BVRI data from our broadband survey carried
out with the 4.2m WHT at La Palma. Distance-independent diagnostics (involving
X/O ratio, hardness ratios, B/T ratio) are tested.Comment: 2 pages, 2 figures, uses graphicx package. To appear in proceedings
of "The X-Ray Universe 2005", San Lorenzo del Escorial, Spain, September
26-30, 200
Near-infrared photometry of isolated spirals with and without an AGN. I: The Data
We present infrared imaging data in the J and K' bands obtained for 18 active
spiral galaxies, together with 11 non active galaxies taken as a control
sample. All of them were chosen to satisfy well defined isolation criteria so
that the observed properties are not related to gravitational interaction. For
each object we give: the image in the K' band, the sharp-divided image
(obtained by dividing the observed image by a filtered one), the difference
image (obtained by subtracting a model to the observed one), the color J-K'
image, the ellipticity and position angle profiles, the surface brightness
profiles in J and K', their fits by bulge+disk models and the color gradient.
We have found that four (one) active (control) galaxies previously classified
as non-barred turn out to have bars when observed in the near-infrared. One of
these four galaxies (UGC 1395) also harbours a secondary bar. For 15 (9 active,
6 control) out of 24 (14 active, 10 control) of the optically classified barred
galaxies (SB or SX) we find that a secondary bar (or a disk, a lense or an
elongated ring) is present. The work presented here is part of a large program
(DEGAS) aimed at finding whether there are differences between active and non
active galaxies in the properties of their central regions that could be
connected with the onset of nuclear activity.Comment: Accepted for publication in Astronomy & Astrophysics Supplement
Serie
The Luminosity Function Evolution of Soft X--ray selected AGN in the RIXOS survey
A sample of 198 soft X--ray selected active galactic nuclei (AGN) from the
ROSAT International X--ray Optical Survey (RIXOS), is used to investigate the
X--ray luminosity function and its evolution. RIXOS, with a flux limit of 3E-14
erg s-1 cm-2 (0.5 to 2.0 keV), samples a broad range in redshift over 20 deg^2
of sky, and is almost completely identified; it is used in combination with the
Einstein Extended Medium Sensitivity Survey (EMSS), to give a total sample of
over 600 AGN. We find the evolution of AGN with redshift to be consistent with
pure luminosity evolution (PLE) models in which the rate of evolution slows
markedly or stops at high redshifts z>1.8. We find that this result is not
affected by the inclusion, or exclusion, of narrow emission line galaxies at
low redshift in the RIXOS and EMSS samples, and is insensitive to uncertainties
in the conversion between flux values measured with ROSAT and Einstein. We
confirm, using a model independent Ve/Va test, that our survey is consistent
with no evolution at high redshifts.Comment: 10 pages, LaTeX file, PS figures and mn.sty. Accepted in MNRA
Star formation in the massive cluster merger Abell 2744
We present a comprehensive study of star-forming (SF) galaxies in the HST
Frontier Field recent cluster merger A2744 (z=0.308). Wide-field,
ultraviolet-infrared (UV-IR) imaging enables a direct constraint of the total
star formation rate (SFR) for 53 cluster galaxies, with SFR{UV+IR}=343+/-10
Msun/yr. Within the central 4 arcmin (1.1 Mpc) radius, the integrated SFR is
complete, yielding a total SFR{UV+IR}=201+/-9 Msun/yr. Focussing on obscured
star formation, this core region exhibits a total SFR{IR}=138+/-8 Msun/yr, a
mass-normalised SFR{IR} of Sigma{SFR}=11.2+/-0.7 Msun/yr per 10^14 Msun and a
fraction of IR-detected SF galaxies f{SF}=0.080(+0.010,-0.037). Overall, the
cluster population at z~0.3 exhibits significant intrinsic scatter in IR
properties (total SFR{IR}, Tdust distribution) apparently unrelated to the
dynamical state: A2744 is noticeably different to the merging Bullet cluster,
but similar to several relaxed clusters. However, in A2744 we identify a trail
of SF sources including jellyfish galaxies with substantial unobscured SF due
to extreme stripping (SFR{UV}/SFR{IR} up to 3.3). The orientation of the trail,
and of material stripped from constituent galaxies, indicates that the passing
shock front of the cluster merger was the trigger. Constraints on star
formation from both IR and UV are crucial for understanding galaxy evolution
within the densest environments.Comment: Accepted by MNRAS. 12 pages, 7 figures (high resolution versions of
Figs. 1 & 2 are available in the published PDF
Linking stellar mass and star formation in Spitzer/MIPS 24 micron galaxies
We present deep Ks<21.5 (Vega) identifications, redshifts and stellar masses
for most of the sources composing the bulk of the 24 micron background in the
GOODS/CDFS. Our identified sample consists of 747 Spitzer/MIPS 24 micron
objects, and includes ~94% of all the 24 micron sources in the GOODS-South
field which have fluxes Snu(24)>83 microJy (the 80% completeness limit of the
Spitzer/GTO 24 micron catalog). 36% of our galaxies have spectroscopic
redshifts (mostly at z<1.5) and the remaining ones have photometric redshifts
of very good quality, with a median of |dz|=|zspec-zphot|/(1+zspec)=0.02. We
find that MIPS 24 micron galaxies span the redshift range z~0-4, and that a
substantial fraction (28%) lie at high redshifts z>1.5. We determine the
existence of a bump in the redshift distribution at z~1.9, indicating the
presence of a significant population of galaxies with PAH emission at these
redshifts. Massive (M>10^11 Msun) star-forming galaxies at redshifts 2<z<3 are
characterized by very high star-formation rates (SFR>500 Msun/yr), and some of
them are able to construct a mass of 10^10-10^11 Msun in a single burst
lifetime (~0.01-0.1 Gyr). At lower redshifts z<2, massive star-forming galaxies
are also present, but appear to be building their stars on long timescales,
either quiescently or in multiple modest burst-like episodes. At redshifts
z~1-2, the ability of the burst-like mode to produce entire galaxies in a
single event is limited to some lower (M<7x10^10 Msun) mass systems, and it is
basically negligible at z<1. Our results support a scenario where
star-formation activity is differential with assembled stellar mass and
redshift, and where the relative importance of the burst-like mode proceeds in
a down-sizing way from high to low redshifts. (abridged)Comment: Accepted for publication in the ApJ. 19 pages, 10 figures. Uses
emulateap
A new way of valorizing biomaterials: the use of sunflower protein for 1 a-tocopherol microencapsulation
Biopolymer based microparticles were efficiently prepared from sunflower protein (SP) wall material and a-tocopherol (T) active core using a spray-drying technique. Protein enzymatic hydrolysis and/or N-acylation were carried out to make some structural modifications to the vegetable protein. Native and hydrolyzed SP were characterized by Asymmetrical Flow Field-Flow Fractionation (AsFlFFF). Results of AsFlFFF confirmed that size of proteinic macromolecules was influenced by degree of hydrolysis. The effect of protein modifications and the influence of wall/core ratio on both emulsions and microparticle properties were evaluated. Concerning emulsion properties, enzymatic hydrolysis involved a decrease in viscosity, whereas acylation did not significantly affect emulsion droplet size and viscosity. Microparticles obtained with hydrolyzed SP wall material showed lower retention efficiency (RE) than native SP microparticles (62-80% and 93% respectively). Conversely, acylation of both hydrolyzed SP and native SP allowed a higher RE to be reached (up to 100%). Increasing T concentration increased emulsion viscosity, emulsion droplet size, microparticle size, and enhanced RE. These results demonstrated the feasibility of high loaded (up to 79.2% T) microparticles
Mid-infrared sources in the ELAIS Deep X-ray Survey
We present a cross‐correlation of the European Large Area Infrared Space Observatory (ISO) survey (ELAIS) with the ELAIS Deep X‐ray Survey of the N1 and N2 fields. There are seven Chandra point sources with matches in the ELAIS Final Analysis 15‐μm catalogue, out of a total of 28 extragalactic ISO sources present in the Chandra fields. Five of these are consistent with active galactic nuclei (AGN) giving an AGN fraction of ∼19 per cent in the 15‐μm flux range 0.8–6 mJy. We have co‐added the hard X‐ray fluxes of the individually undetected ISO sources and find a low significance detection consistent with star formation in the remaining population. We combine our point source cross‐correlation fraction with the XMM–Newton observations of the Lockman Hole and Chandra observations of the Hubble Deep Field North to constrain source count models of the mid‐infrared galaxy population. The low dust‐enshrouded AGN fraction in ELAIS implied by the number of cross‐identifications between the ELAIS mid‐infrared sample and the Chandra point sources is encouraging for the use of mid‐infrared surveys to constrain the cosmic star formation history, provided there are not further large undetected populations of Compton‐thick AGN
Observational constraints to boxy/peanut bulge formation time
Boxy/peanut bulges are considered to be part of the same stellar structure as
bars and both could be linked through the buckling instability. The Milky Way
is our closest example. The goal of this letter is determining if the mass
assembly of the different components leaves an imprint in their stellar
populations allowing to estimate the time of bar formation and its evolution.
To this aim we use integral field spectroscopy to derive the stellar age
distributions, SADs, along the bar and disc of NGC 6032. The analysis shows
clearly different SADs for the different bar areas. There is an underlying old
(>=12 Gyr) stellar population for the whole galaxy. The bulge shows star
formation happening at all times. The inner bar structure shows stars of ages
older than 6 Gyrs with a deficit of younger populations. The outer bar region
presents a SAD similar to that of the disc. To interpret our results, we use a
generic numerical simulation of a barred galaxy. Thus, we constrain, for the
first time, the epoch of bar formation, the buckling instability period and the
posterior growth from disc material. We establish that the bar of NGC 6032 is
old, formed around 10 Gyr ago while the buckling phase possibly happened around
8 Gyr ago. All these results point towards bars being long-lasting even in the
presence of gas.Comment: Accepted for publication in MNRAS Letter
Near-infrared photometry of isolated spirals with and without an AGN. II: Photometric properties of the host galaxies
We present the analysis of morphological and photometric properties of a
sample of isolated spirals with (18) and without (11) an active nucleus, based
on near-infrared imaging in the J and K' bands. The aim of this analysis is to
find the differential properties that could be directly connected with the
phenomenon of nuclear activity. We stress the importance of using isolated
objects for that purpose. Our study shows that both sets of galaxies are
similar in their global properties: they define the same Kormendy relation,
their disk components share the same properties, the bulge and disk scale
lengths are correlated in a similar way, bar strengths and lengths are similar
for primary bars. Hosts of isolated Seyfert galaxies have bulge and disk
properties comparable to those of isolated non active spirals. Central colors
(the innermost 200 pc) of active galaxies are redder than the centers of non
active spirals, most probably due to AGN light being re-emitted by the hot dust
and/or due to circumnuclear star formation, through the contribution of
giants/supergiants. Only one of the Seyfert galaxies in our sample does not
present a primary bar,but both primary and secondary bars are equally present
in active and control objects. Secondary central elongations (associated with
secondary bars, lenses, rings or disks) may be somewhat different. Numerical
models indicate that such secondary bars are not strictly necessary to feed the
central engine when a primary bar is present. Our results show that down to
scales of 100-300 pc, there are no obvious differences between active and non
active spiral galaxies.Comment: 9 pages, accepted for publication in Astronomy and Astrophysic
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