arXiv subjects

C. M. Gutierrez

Publications and source records attributed to C. M. Gutierrez.

At least 37 records · Page 2Linked to original sources

arXiv2013

A characterization of the diffuse Galactic emissions at large angular scales using the Tenerife data

The Anomalous microwave emission (AME) has been proved to be an important component of the Galactic diffuse emission in the range from 20 to 60 GHz. To discriminate between different models of AME low frequency microwave data from 10 to 20 GHz are needed. We present here a re-analysis of published and un-published Tenerife data from 10 to 33 GHz at large angular scales (from 5 to 15 degrees). We cross-correlate the Tenerife data to templates of the main Galactic diffuse emissions: synchrotron, free-free and thermal dust. We find evidence of dust correlated emission in the Tenerife data that could be explained as spinning dust grain emission.

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arXiv2011

On the non-evolution of the dependence of black hole masses on bolometric luminosities for QSOs

There are extremely luminous quasi stellar objects (QSOs) at high redshift which are absent at low redshift. The lower luminosities at low redshifts can be understood as the external manifestation of either a lower Eddington ratio or a lower mass. To distinguish between both effects, we determine the possible dependence of masses and Eddington ratios of QSOs with a fixed luminosity as a function of redshifts; this avoids the Malmquist bias or any other selection effect. For the masses and Eddington ratios derived for a sample of QSOs in the Sloan Digital Sky Survey, we model their evolution by a double linear fit separating the dependence on redshifts and luminosities. The validity of the fits and possible systematic effects were tested by the use of different estimators of masses or bolometric luminosities, and possible intergalactic extinction effects. The results do not show any significant evolution of black hole masses or Eddington ratios for equal luminosity QSOs. The black hole mass only depends on the bolometric luminosity without significant dependence on the redshift as M_{BH}(10^9 M_sun) = 3.4[L_{bol}(10^{47} erg/s})]^{0.65} on average for z<5. This must not be confused with the possible evolution in the formation of black holes in QSOs. The variations of environment might influence the formation of the black holes but not its subsequent accretion. It also leaves a question to be solved: Why are there not QSOs with very high mass at low redshift? A brief discussion of the possible reasons for this is tentatively pointed out.

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arXiv2011

The most distant compact groups

We present photometric and spectroscopic observations of the members of three previously cataloged compact group (CG) candidates at redshifts z>0.3. These confirm spectroscopic redshifts compatible with being gravitationally bound structures at redshifts 0.3112, 0.3848 and 0.3643 respectively, and then they are the most distant CGs known with spectroscopic confirmation for all their members. The morphological and spectroscopic properties of all their galaxies indicate early types dominated by an old population of stars, with little star formation or nuclear activity. Most of the physical properties derived for the three groups are quite similar to the average properties of CGs at lower redshifts. In particular, from the velocities and positions of the respective members of each CG, we estimate short dynamic times. These leave open the questions of identifying the mechanism for forming CGs continuously and the nature of the final stages of these structures.

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arXiv2010

The value of the fine structure constant over cosmological times

The optical spectra of objects classified as QSOs in the SDSS DR6 are analyzed with the aim of determining the value of the fine structure constant in the past and then check for possible changes in the constant over cosmological timescales. The analysis is done by measuring the position of the fine structure lines of the [OIII] doublet (4959 and 5008) in QSO nebular emission. From the sample of QSOs at redshifts z < 0.8 a subsample was selected on the basis of the amplitude and width of the [OIII] lines. Two different method were used to determine the position of the lines of the [OIII] doublet, both giving similar results. Using a clean sample containing 1568 of such spectra, a value of Delta alpha /alpha=(+2.4 +-2.5) x 10^{-5} (in the range of redshifts 0-0.8) was determined. The use of a larger number of spectra allows a factor ~5 improvement on previous constraints based on the same method. On the whole, we find no evidence of changes in alpha on such cosmological timescales. The mean variation compatible with our results is 1/ Delta alpha/alpha=(+0.7 +- 0.7) x 10^{-14} yr^{-1}. The analysis was extended to the [NeIII] and [SII] doublets, although their usefulness is limited due to the fact that all these doublets in QSOs tend to be fainter than [OIII], and that some of them are affected by systematics.

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arXiv2009

The spatial distribution of galaxies within the CMB cold spot in the Corona Borealis supercluster

We study the spatial distribution and colours of galaxies within the region covered by the cold spot in the cosmic microwave background (CMB) recently detected by the Very Small Array (VSA; Genova-Santos et al. 2005, 2008) towards the Corona Borealis supercluster (CrB-SC). The spot is in the northern part of a region with a radius ~1 degree (~5 Mpc at the redshift of CrB-SC) enclosing the clusters Abell 2056, 2065, 2059 and 2073, and where the density of galaxies, excluding the contribution from those clusters, is ~2 times higher than the mean value in typical intercluster regions of the CrB-SC. Two of such clusters (Abell 2056 and 2065) are members of the CrB-SC, while the other two are in the background. This high density intercluster region is quite inhomogeneous, being the most remarkable feature a large concentration of galaxies in a narrow filament running from Abell 2065 with a length of ~35 arcmin (~3 Mpc at the redshift of CrB-SC) in the SW-NE direction. This intercluster population of galaxies probably results from the interaction of clusters Abell 2065 and 2056. The area subtended by the VSA cold spot shows an excess of faint (21<r<22) and red (1.1<r-i<1.3) galaxies as compared with typical values within the CrB-SC intercluster regions. This overdensity of galaxies shows a radial dependence and extends out to ~15 arcmin. This could be signature of a previously unnoticed cluster in the background.

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arXiv2008

Analysis of possible anomalies in the QSO distribution of the Flesch & Hardcastle catalogue

AIMS. A recent catalogue by Flesch & Hardcastle presents two major anomalies in the spatial distribution of QSO candidates: i/ an apparent excess of such objects near bright galaxies, and ii/ an excess of very bright QSO candidates compared to random background expectations in several regions of the sky. Because anyone of these anomalies would be relevant in a cosmological context, we carried out an extensive analysis of the probabilities quoted in that catalogue. METHODS. We determine the nature and redshift of a subsample of 30 sources in that catalogue by analysing their optical spectra (another 11 candidates were identified from existing public databases). These have allowed us to statistically check the reliability of the probabilities QSO status quoted by Flesch & Hardcastle for their candidates. RESULTS. Only 12 of the 41 candidates turned out QSOs (7 of which have been identified here for the first time). CONCLUSIONS. The probabilities of the QSOs' being the candidates given by Flesch & Hardcastle are overestimated for m_B<17 and for objects projected near (<1 arcmin) bright galaxies. This is the cause of the anomalies mentioned above.

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arXiv2006

First tentative detection of anisotropy in the QSO distribution around nearby edge-on spiral galaxies

AIMS. To check whether the polar angle distribution of QSOs around nearby spiral galaxies is isotropic or not. METHODS. A statistical analysis of the polar angle distribution of large samples of QSOs from the SDSS survey and Monte Carlo simulations to calculate their significance are carried out. RESULTS. There is a clear excess of QSOs near the minor axis with respect to the major axis of nearby edge-on spiral galaxies, significant at a level 3.5-sigma up to angular distances of 3 deg. (or ~1.7 Mpc) from the centre of each galaxy. The significance is increased to 3.9-sigma with the z>0.5 QSOs, and it reaches 4.8-sigma if we include galaxies whose circles of radius 3 degrees are covered by the SDSS in more than 98% (instead of 100%) of the area. CONCLUSIONS. Gravitational lensing in the halo of nearby galaxies or extinction seem insufficient to explain the observed anisotropic distribution of QSOs. The anisotropic distribution agrees qualitatively with the predictions of Arp's models, which claim that QSOs are ejected by galaxies along the rotation axis, although Arp's prediction give a distance of the QSOs ~3 times smaller than that found here. In any case, a chance fluctuation, although highly improbable, might be a possibility rather than a true anisotropy, and the present results should be corroborated by other groups and samples, so we prefer to consider it as just a first tentative detection.

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arXiv2006

Star Formation in Satellite Galaxies

We present narrow-band observations of the H$α$ emission in a sample of 31 satellite orbiting isolated giant spiral galaxies. The sample studied spans the range $-19<M_B <-15$ mag. The H$α$ emission was detected in all the spiral and irregular objects with fluxes in the range $1.15-49.80\times 10^{-14}$ erg cm$^{-2}$ s$^{-1}$. The average and maximum values for the current star formation rates are 0.68 and 3.66 M$_\sun$ yr$^{-1}$ respectively. Maps of the spatial distribution of ionized gas are presented. The star-forming regions show a rich structure in which frequently discrete complexes are imposed over more diffuse structures. In general, the current star formation rates are smaller that the mean values in the past obtained from the current stellar content; this probably indicates a declining rhythm with time in the generation of new stars. However, the reserve of gas is enough to continue fueling the current levels of star formation activity for at least another Hubble time. Four of the objects (NGC 2718b, NGC 4541e, NGC 5965a$_1$ and NGC 5965a$_2$) with higher current star formation rates show clear signs of interaction with close companions of comparable brightness at projected distances of 25, 20 and 2 kpc respectively. The only two galaxies in our sample that do not show star formation activity are members of these interacting systems, and it is unclear if this is a consequence of intrinsic properties (both are Hubble early types) or if it is related with possible disruption of the external parts due to the interaction. In the case of the pair NGC 2718a-b there are indications of gas transport between both galaxies.

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arXiv2006

Toward a Clean Sample of Ultra-Luminous X-ray Sources

CONTEXT. Observational follow-up programmes for the characterization of ultra-luminous X-ray sources (ULXs) require the construction of clean samples of such sources in which the contamination by foreground/background sources is minimum. AIMS. In this article we calculate the degree of foreground/background contaminants among the ULX sample candidates in the Colbert & Ptak (2002) catalogue and compare these computations with available spectroscopical identifications. METHODS. We use statistics based on known densities of X-ray sources and AGN/QSOs selected in the optical. The analysis is done individually for each parent galaxy. The existing identifications of the optical counterparts are compiled from the literature. RESULTS. More than a half of the ULXs, within twice the distance of the major axis of the 25 mag/arcsec$^2$ isophote from RC3 nearby galaxies and with X-ray luminosities $L_X$[2-10 keV] $\ge 10^{39}$ erg/s, are expected to be high redshift background QSOs. A list of 25 objects (clean sample) confirmed to be real ULXs or to have a low probability of being contaminant foreground/background objects is provided.

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arXiv2006

Observations of the Cosmic Microwave Background and Galactic Foregrounds at 12-17 GHz with the COSMOSOMAS Experiment

(Abridged) We present the analysis of the first 18 months of data obtained with the COSMOSOMAS experiment at the Teide Observatory (Tenerife). Three maps have been obtained at 12.7, 14.7 and 16.3 GHz covering 9000 square degrees each with a resolution of ~1 degree and with sensitivities 49, 59 and 115 muK per beam respectively. These data in conjuction with the WMAP first year maps have revealed that the Cosmic Microwave Background (CMB) is the dominant astronomical signal at high galatic latitude in the three COSMOSOMAS channels with an average amplitude of 29.7+/- 1.0 \muK (68% c.l. not including calibration errors). This value is in agreement with the predicted CMB signal in the COSMOSOMAS maps using the best fit Lambda-CDM model to the WMAP power spectrum. Cross-correlation of COSMOSOMAS data with the DIRBE map at 100 μm shows the existence of a common signal with amplitude 7.4+/- 1.1, 7.5+/- 1.1, and 6.5+/-2.3 muK in the 12.7, 14.7 and 16.3 GHz COSMOSOMAS maps at |b|>30^°. Using the WMAP data we find this DIRBE correlated signal rises from high to low frequencies flattening below ~20 GHz. At higher galactic latitudes the average amplitude of the correlated signal with the DIRBE maps decreases slightly. The frequency behaviour of the COSMOSOMAS/WMAP correlated signal with DIRBE is not compatible with the expected tendency for thermal dust. A study of the H-alpha emission maps do not support free-free as a major contributor to that signal. Our results provide evidence of a new galactic foreground with properties compatible with those predicted by the spinning dust models.

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arXiv2005

Research on candidates for non-cosmological redshifts

(Abridged:) The paradox of apparent optical associations of galaxies with very different redshifts, the so-called anomalous redshift problem, is around 35 years old, but is still without a clear solution and is surprisingly ignored by most of the astronomical community. Statistical correlations among the positions of these galaxies have been pointed out by several authors. Gravitational lensing by dark matter has been proposed as the cause of these correlations, although this seems to be insufficient to explain them and does not work at all for correlations with the brightest and nearest galaxies. Some of these cases may be just fortuitous associations in which background objects are close in the sky to a foreground galaxy, although the statistical mean correlations remain to be explained and some lone objects have very small probabilities of being a projection of background objects. The sample of discordant redshift associations given in Arp's atlas is indeed quite large, and most of the objects remain to be analysed thoroughly. For about 5 years, we have been running a project to observe some of these cases in detail, and some new anomalies have been added to those already known; For instance, in some exotic configurations such as NGC 7603 or NEQ3, which can even show bridges connecting four object with very different redshifts. Not only QSOs but also emission-line galaxies in general are found to take part in this kind of event. Other cases are analyzed: MCG 7-25-46, GC 0248+430, B2 1637+29, VV172 and Stephan's Quintet.

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arXiv2005

Detection of anomalous microwave emission in the Perseus molecular cloud with the COSMOSOMAS experiment

We present direct evidence for anomalous microwave emission in the Perseus molecular cloud, which shows a clear rising spectrum from 11 to 17 GHz in the data of the COSMOSOMAS experiment. By extending the frequency coverage using WMAP maps convolved with the COSMOSOMAS scanning pattern we reveal a peak flux density of 42 (+/-) 4 Jy at 22 GHz integrated over an extended area of 1.65 x 1.0 deg centered on RA = 55.4 (+/-) 0.1 deg and Dec = 31.8 (+/-) 0.1 deg (J2000). The flux density that we measure at this frequency is nearly an order of magnitude higher than can be explained in terms of normal galactic emission processes (synchrotron, free-free and thermal dust). An extended IRAS dust feature G159.6-18.5 is found near this position and no bright unresolved source which could be an ultracompact HII region or gigahertz peaked source could be found. An adequate fit for the spectral density distribution can be achieved from 10 to 50 GHz by including a very significant contribution from electric dipole emission from small spinning dust grains.

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arXiv2005

The Nature of Ultra Luminous X-ray Sources

We present spectroscopic observations of six optical counterparts of intermediate luminosity X-ray sources (ULXs) around nearby galaxies. The spectra of the six objects show the presence of broad emission features. The identification of these allow us to classify all of the objects as quasars at higher redshift than their assigned parent galaxy. This is one of the first and largest identifications of such objects using unambigous optical spectral features. These results, in conjuction with previous similar identifications of other sources, indicate that high redshift quasars represent an important fraction of catalogued ULX sources. We estimate the density of such sources and compare this with expectations for a population of randomly distributed background quasars.

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arXiv2004

Searching for High Redshift Clusters

Distant clusters of galaxies provide a powerful method to study the formation and evolution of galaxies, and large scale structure of the Universe. However, the number of known clusters at high redshift (z> 0.5) is still very reduced. As a preparatory work for detailed studies wigh GTC, we are searching for high redshift clusters in public wide optical surveys. We will complement this with near IR observations in 4 m telescopes. Here, we present some preliminary results. In a field of 35 x 35 arcmin^2 we have detected 8 clusters of galaxies at redshift z> 0.5.

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arXiv2004

Formation and Evolution of Structures in the Universe

We summarize our work on structures in different stages of aggregation, and spanning a wide range in redshift. We emphasize our work on high resdhift clusters. This comprises the analysis of ~7 square degrees using deep images with several broad-band optical filters. We plan to complement these with near IR observations in 4 m telescopes. Preliminary results of the analysis in a field of 35 x 35 arcmin^2 indicate the detection of several candidates to be clusters at redshifst z> 0.5. When all the fields are analyzed, we will have an adequate sample for future detailed studies with the GTC.

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arXiv2004

The Properties of Satellite Galaxies in External Systems. II. Photometry and Colors

In this second paper dedicated to the study of satellite galaxies we present broad-band photometry in the B, V, R and I filters of 49 satellite galaxies orbiting giant isolated spiral galaxies. First analysis of the properties of these objects are presented by means of color--color and color--magnitude diagrams for early- and late-type satellites. Although we find differences in the slope of the V-I vs. Mv color magnitude diagram, as a whole, the relations are in agreement with the trends known to date for galaxies of similar magnitudes in nearby clusters of galaxies. Comparison with the relations found for satellites in the Local Group allows us to sample better the bright end of the luminosity function of satellite galaxies and extends for brighter objects the validity of the color--magnitude relation found for dwarf galaxies in the Local Group. Most of the E/S0 galaxies in our sample show a negative color gradient with values similar to those known for early type galaxies in other environments.

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arXiv2004

QSO + galaxy association and discrepant redshifts in NEQ3

Spectroscopy and deep imaging of the group NEQ3 are presented. This system is formed by three compact objects with relative separations of ~2.6 and ~2.8 arcsec, and a lenticular galaxy at ~17 arcsec from the geometric centre of the group. A diffuse filament is located on a line joining the three compact objects and the main galaxy. Analysis of these observations confirms the redshift previously known for three of the objects (z=0.1239 for the main galaxy, and z=0.1935 and 0.1939 for two of the compact objects). We have also determined the previously unknown redshift of the third compact object as z=0.2229. Using the relative strength and width of the main spectral lines, we have classified the compact objects as two HII galaxies and one QSO (the object at z=0.1935). With cross-correlation techniques, we have tentatively estimated the redshift of the filament as z=0.19 (although a weaker component also appears at z=0.12) so that it is probably associated with the halo of the two compact objects at this redshift. The two objects at redshift ~0.19 represent possibly one of the more clear examples of starburst (and perhaps QSO activity) driven by interaction. These, and the relation between these two objects and the other two at (~0.12 and ~0.22) make the nature of this system intriguing, being difficult to explain the whole association on conventional scenarios.

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arXiv2004

The field surrounding NGC 7603: cosmological or non-cosmological redshifts?

We present new observations of the field surrounding the Seyfert galaxy NGC 7603, where four galaxies with different redshifts--NGC 7603 (z=0.029), NGC 7603B (z=0.057) and two fainter emission line galaxies (z=0.245 and z=0.394)--are apparently connected by a narrow filament, leading to a possible case of anomalous redshift. The observations comprise broad and narrow band imaging and intermediate resolution spectroscopy of some of the objects in the field. The new data confirm the redshift of the two emission-line objects found within the filament connecting NGC 7603 and NGC 7603B, and settles their type with better accuracy. Although both objects are point-like in ground based images, using HST archive images we show that the objects have structure with a FWHM=0.3-0.4 arcsec. This and the relative strength and width of the main spectral lines allow us to classify these as HII galaxies with very vigorous star formation, while the rest of the filament and NGC 7603B lack star formation. We delineate the halo of NGC 7603 out to 26.2 mag/square arcsec in the Sloan r band filter and find evidence for strong internal distortions. New narrow emission line galaxies at z=0.246, 0.117 and 0.401 are also found at respectively 0.8, 1.5 and 1.7 arcmin to the West of the filament within the fainter contour of this halo. The probability of three background galaxies of any type with apparent B-magnitudes up to 16.6, 21.1 and 22.1 (the observed magnitudes, extinction correction included) being randomly projected on the filament of the fourth galaxy (NGC 7603) is computed resulting ~ 3 x 10^(-9).

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