arXiv subjects

Jose Maza

Publications and source records attributed to Jose Maza.

At least 19 recordsLinked to original sources

arXiv2009

SN 2003bg: The First Type IIb Hypernova

Optical and near-infrared photometry and optical spectroscopy are reported for SN 2003bg, starting a few days after explosion and extending for a period of more than 300 days. Our early-time spectra reveal the presence of broad, high-velocity Balmer lines. The nebular-phase spectra, on the other hand, show a remarkable resemblance to those of Type Ib/c supernovae, without clear evidence for hydrogen. Near maximum brightness SN 2003bg displayed a bolometric luminosity comparable to that of other Type I hypernovae unrelated to gamma-ray bursts, implying a rather normal amount of 56Ni production (0.1-0.2 Msun) compared with other such objects. The bolometric light curve of SN 2003bg, on the other hand, is remarkably broad, thus suggesting a relatively large progenitor mass at the moment of explosion. These observations, together with the large value of the kinetic energy of expansion established in the accompanying paper (Mazzali et al. 2009), suggest that SN 2003bg can be regarded as a Type IIb hypernova.

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arXiv2009

Ultraviolet Fe II emission in z ~ 2 quasars

We present spectra of six luminous quasars at z ~ 2, covering rest wavelengths 1600-3200 A. The fluxes of the UV Fe II emission lines and Mg II 2798 doublet, the line widths of Mg II, and the 3000 A luminosity were obtained from the spectra. These quantities were compared with those of low-redshift quasars at z = 0.06 - 0.55 studied by Tsuzuki et al. In a plot of the Fe II(UV)/Mg II flux ratio as a function of the cental black hole mass, Fe II(UV)/Mg II in our z ~ 2 quasars is systematically greater than in the low-redshift quasars. We confermed that luminosity is not responsible for this excess. It is unclear whether this excess is caused by rich Fe abundance at z ~ 2 over low-redshift or by non-abundance effects such as high gas density, strong radiation field, and high microturbulent velocity.

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arXiv2008

Broad-line region size and black hole mass in high-z AGN

In this contribution we briefly review the reverberation mapping technique and its results for low and intermidiate luminosity AGNs. Then we present a monitoring campaign of high-luminosity high-redshift quasars which will extend these results by two orders of magnitude, probing the broad-line region size and black hole (BH) mass of luminous AGN at redshift ~2-3.

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arXiv2006

Clustering of K-selected Galaxies at 2<z<3.5: Evidence for a Color-Density Relation

We study the clustering properties of K-selected galaxies at 2 2.3 distant red galaxies (DRGs) have r_0 ~ 11 h^-1 Mpc. Contrary to findings for optically-selected galaxies, K-selected galaxies that are faint in the R-band cluster more strongly than brighter galaxies. These results suggest that a color-density relation was in place at z>2. Our results indicate that K-bright blue galaxies and K-bright red galaxies are fundamentally different, as they have different clustering properties. Using a simple model of one galaxy per halo, we infer halo masses ~ 5 x 10^12 M_sun for K<21 galaxies and ~ 2 x 10^13 M_sun for DRGs. A comparison of the observed space density of DRGs to the density of their host halos suggests large halo occupation numbers; however, this result is at odds with the lack of a strong small-scale excess in the angular correlation function. We find that the z=0 descendants of the galaxies considered here reside primarily in groups and clusters. [abridged]

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arXiv2006

The Multiwavelength Survey by Yale-Chile (MUSYC): Deep Near-Infrared Imaging and the Selection of Distant Galaxies

We present deep near-infrared JHK imaging of four 10'x10' fields. The observations were carried out as part of the Multiwavelength Survey by Yale-Chile (MUSYC) with ISPI on the CTIO 4m telescope. The typical point source limiting depths are J~22.5, H~21.5, and K~21 (5sigma; Vega). The effective seeing in the final images is ~1.0". We combine these data with MUSYC UBVRIz imaging to create K-selected catalogs that are unique for their uniform size, depth, filter coverage, and image quality. We investigate the rest-frame optical colors and photometric redshifts of galaxies that are selected using common color selection techniques, including distant red galaxies (DRGs), star-forming and passive BzKs, and the rest-frame UV-selected BM, BX, and Lyman break galaxies (LBGs). These techniques are effective at isolating large samples of high redshift galaxies, but none provide complete or uniform samples across the targeted redshift ranges. The DRG and BM/BX/LBG criteria identify populations of red and blue galaxies, respectively, as they were designed to do. The star-forming BzKs have a very wide redshift distribution, a wide range of colors, and may include galaxies with very low specific star formation rates. In comparison, the passive BzKs are fewer in number, have a different distribution of K magnitudes, and have a somewhat different redshift distribution. By combining these color selection criteria, it appears possible to define a reasonably complete sample of galaxies to our flux limit over specific redshift ranges. However, the redshift dependence of both the completeness and sampled range of rest-frame colors poses an ultimate limit to the usefulness of these techniques.

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arXiv2006

The Physical Nature of Lyman Alpha Emitting Galaxies at z=3.1

We selected 40 candidate Lyman Alpha Emitting galaxies (LAEs) at z ~=3.1 with observed frame equivalent widths >150A and inferred emission line fluxes >2.5x10^-17 ergs/cm^2/s from deep narrow-band and broad-band MUSYC images of the Extended Chandra Deep Field South. Covering 992 sq. arcmin, this is the largest ``blank field'' surveyed for LAEs at z ~3, allowing an improved estimate of the space density of this population of 3+-1x10^-4 h_70^3/Mpc^3. Spectroscopic follow-up of 23 candidates yielded 18 redshifts, all at z ~=3.1. Over 80% of the LAEs are dimmer in continuum magnitude than the typical Lyman break galaxy spectroscopic limit of R= 25.5 (AB), with a median continuum magnitude R ~=27 and very blue continuum colors, (V-z) ~=0. Over 80% of the LAEs have the right UVR colors to be selected as Lyman break galaxies, but only 10% also have R<=25.5. Stacking the UBVRIzJK fluxes reveals that LAEs have stellar masses ~=5x10^8 h_70^-2 M_sun and minimal dust extinction, A_V < ~ 0.1. Inferred star formation rates are ~=6 h_70^-2 M_sun/yr, yielding a cosmic star formation rate density of 2x10^-3 h_70 M_sun/yr/Mpc^3. None of our LAE candidates show evidence for rest-frame emission line equivalent widths EW_rest>240A which might imply a non-standard IMF. One candidate is detected by Chandra, implying an AGN fraction of 2+-2% for LAE candidate samples. In summary, LAEs at z ~ 3 have rapid star formation, low stellar mass, little dust obscuration and no evidence for a substantial AGN component.

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arXiv2005

Star Formation in Distant Red Galaxies: Spitzer observations in the Hubble Deep Field South

We present Spitzer 24micron imaging of 1.5 < z < 2.5 Distant Red Galaxies (DRGs) in the 10arcmin by 10arcmin Extended Hubble Deep Field South of the Multiwavelength Survey by Yale-Chile. We detect 65% of the DRGs with K_AB < 23.2 mag at S_24micron > 40uJy, and conclude that the bulk of the DRG population are dusty active galaxies. A mid-infrared (MIR) color analysis with IRAC data suggests that the MIR fluxes are not dominated by buried AGN, and we interpret the high detection rate as evidence for a high average star formation rate of = 130+/-30 M/yr. From this, we infer that DRGs are important contributors to the cosmic star formation rate density at z ~ 2, at a level of \~0.02 M/yr/Mpc^3 to our completeness limit of K_AB = 22.9 mag

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arXiv2004

The Calan-Yale Deep Extragalactic Research (CYDER) Survey: Optical Properties and Deep Spectroscopy of Serendipitous X-ray Sources

We present the first results from the Calán-Yale Deep Extragalactic Research (CYDER) survey. The main goal of this survey is to study serendipitous X-ray sources detected by Chandra in an intermediate flux range ($10^{-15}-10^{-12}$ ergs s$^{-1}$) that comprises most of the X-ray background. 267 X-ray sources spread over 5 archived fields were detected. The $\log N-\log S$ distribution obtained for this sample is consistent with the results of other surveys. Deep $V$ and $I$ images were taken of these fields in order to calculate X-ray-to-optical flux ratios. Identifications and redshifts were obtained for 106 sources using optical spectroscopy from 8-m class telescopes to reach the optically faintest sources, to the same level as deeper X-ray fields like the Chandra Deep Fields, showing that the nature of sources detected depends mostly on the optical limit for spectroscopy. In general, sources optically classified as obscured Active Galactic Nuclei (AGNs) have redder optical colors than unobscured AGN. A rough correlation between $f_X/f_{\rm opt}$ and hard X-ray luminosity was found for obscured AGN confirming the prediction by existing models that in obscured AGN the optical light is completely dominated by the host galaxy. The previously claimed decrease of the obscured to unobscured AGN ratio with increasing X-ray luminosity is observed. However, this correlation can be explained as a selection effect caused by the lower optical flux of obscured AGN. Comparison between the observed $N_H$ distribution and predictions by existing models shows that the sample appears complete up to $N_H<3\times 10^{22}$ cm$^{-2}$, while for more obscured sources incompleteness plays an important role in the observed obscured to unobscured AGN ratio.

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arXiv2004

The Fundamental Plane Evolution of Active Galactic Nucleus Host Galaxies

We measured the stellar velocity dispersions of 15 active galactic nucleus (AGN) host galaxies at redshifts as high as $\sim 0.34$. Combining these with published velocity dispersion measurements from the literature, we study the Fundamental Plane of AGN host galaxies and its evolution. BL Lac hosts and radio galaxies seem to lie on the same Fundamental Plane as normal early-type galaxies. The evolution of the mass-to-light ratio of AGN host galaxies shows a similar trend to that observed in normal early-type galaxies, consistent with single-burst passive evolution models with formation redshifts $z \gtrsim 1$. The lack of a significant difference between normal and AGN host galaxies in the Fundamental plane supports the "Grand Unification" picture wherein AGNs are a transient phase in the evolution of normal galaxies. The black hole masses of BL Lac objects and radio galaxies, derived using the mass -- dispersion relation, are similar. The black hole mass is independent of BL Lac type. The local black hole mass -- host galaxy luminosity relation of our sub-sample at $z < 0.1$ is similar to that of local normal and radio galaxies, but is less well defined at higher redshift due to the luminosity evolution of the host galaxies.

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arXiv2003

Optical and Infrared Photometry of the Nearby Type Ia Supernovae 1999ee, 2000bh, 2000ca, and 2001ba

We present near infrared photometry of the Type Ia supernova 1999ee; also, optical and infrared photometry of the Type Ia SNe 2000bh, 2000ca, and 2001ba. For SNe 1999ee and 2000bh we present the first-ever SN photometry at 1.035 microns (the Y-band). We present K-corrections which transform the infrared photometry in the observer's frame to the supernova rest frame. Using our infrared K-corrections and stretch factors derived from optical photometry, we construct JHK templates which can be used to determine the apparent magnitudes at maximum if one has some data in the window -12 to +10 d with respect to T(B_max). Following up previous work on the uniformity of V minus IR loci of Type Ia supernovae of mid-range decline rates, we present unreddened loci for slow decliners. We also discuss evidence for a continuous change of color at a given epoch as a function of decline rate.

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arXiv2003

An X-ray Selected AGN at z=4.6 Discovered by the CYDER Survey

We present the discovery of a high redshift, X-ray selected AGN by the Calan-Yale Deep Extragalactic Research (CYDER) survey: CXOCY J033716.7-050153, located at $z=4.61$, the second high redshift AGN discovered by this survey. Here, we present its optical, near-IR and X-ray properties and compare it with other optical and X-ray selected high redshift AGN. The optical luminosity of this object is significantly lower than most optically selected high redshift quasars. It also has a lower rest frame UV to X-ray emission ratio than most known quasars at this redshift. This mild deviation can be explained either by dust obscuring the UV radiation of a normal radio quiet AGN emitting at 10% of its Eddington luminosity or because this is intrinsically a low luminosity radio loud AGN, with a super-massive Black Hole of $\sim 10^8M_\sun$ emitting at 1% of its Eddington luminosity. Deep radio observations can discriminate between these two hypotheses.

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arXiv2003

Imaging and Demography of the Host Galaxies of High-Redshift Type Ia Supernovae

We present the results of a study of the host galaxies of high redshift Type Ia supernovae (SNe Ia). We provide a catalog of 18 hosts of SNe Ia observed with the Hubble Space Telescope (HST) by the High-z Supernova Search Team (HZT), including images, scale-lengths, measurements of integrated (Hubble equivalent) BVRIZ photometry in bands where the galaxies are brighter than m ~ 25 mag, and galactocentric distances of the supernovae. We compare the residuals of SN Ia distance measurements from cosmological fits to measurable properties of the supernova host galaxies that might be expected to correlate with variable properties of the progenitor population, such as host galaxy color and position of the supernova. We find mostly null results; the current data are generally consistent with no correlations of the distance residuals with host galaxy properties in the redshift range 0.42 < z < 1.06. Although a subsample of SN hosts shows a formally significant (3-sigma) correlation between apparent V-R host color and distance residuals, the correlation is not consistent with the null results from other host colors probed by our largest samples. There is also evidence for the same correlations between SN Ia properties and host type at low redshift and high redshift. These similarities support the current practice of extrapolating properties of the nearby population to high redshifts pending more robust detections of any correlations between distance residuals from cosmological fits and host properties.

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arXiv2003

Evidence for an asymptotic giant branch star in the progenitor system of a type Ia supernova

A type Ia supernova (SN Ia), one of the two main classes of exploding stars, is recognized by the absence of hydrogen and the presence of elements such as silicon and sulphur in its spectra. These explosions are thought to produce the majority of iron-peak elements in the universe and are known to be precise "standard candles" used to measure distances to galaxies. While there is general agreement that SNe Ia are exploding white dwarfs, astronomers face the embarassing problem that the progenitor systems have never been directly observed. Significant effort has been put into the detection of circum-stellar material (CSM) in order to discriminate between the different types of possible progenitors systems, yet no CSM has been found. Here we report optical observations of SN 2002ic which reveal large amounts of CSM seen as a strong hydrogen emission. This observation suggests that the progenitor system contained a massive asymptotic branch giant star which lost a few solar masses of hydrogen-rich gas prior to the type Ia explosion.

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arXiv2002

Evidence for Core Collapse in the Type Ib/c SN 1999ex

We present optical and infrared spectra of SN 1999ex that reveal a clear example of an intermediate Type Ib/c case. This suggests a continuous spectroscopic sequence between Type Ib and Type Ic supernovae. We report UBVRIz photometric observations of SN 1999ex that started only one day after explosion, which permitted us to witness an elusive transient cooling phase that lasted 4 days. The initial cooling and subsequent radioactive heating produced a dip in the lightcurve which is consistent with explosion models involving core collapse of evolved massive helium stars, and inconsistent with lightcurves resulting from the thermonuclear runaway of compact white dwarfs.

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arXiv2002

Optical and Infrared Spectroscopy of SN 1999ee and SN 1999ex

We report optical and infrared spectroscopic observations of the Type Ia SN 1999ee and the Type Ib/c SN 1999ex, both of which were hosted by the galaxy IC 5179. For SN 1999ee we obtained a continuous sequence with an unprecedented wavelength and temporal coverage beginning 9 days before maximum light and extending through day 42. Before maximum light SN 1999ee displayed a normal spectrum with a strong Si II 6355 absorption, thus showing that not all slow-declining SNe are spectroscopically peculiar at these evolutionary phases. A comparative study of the infrared spectra of SN 1999ee and other Type Ia supernovae shows that there is a remarkable homogeneity among the Branch-normal SNe Ia during their first 60 days of evolution. SN 1991bg-like objects, on the other hand, display spectroscopic peculiarities at infrared wavelengths. SN 1999ex was characterized by the lack of hydrogen lines, weak optical He I lines, and strong He I 10830,20581, thus providing an example of an intermediate case between pure Ib and Ic supernovae. We conclude therefore that SN 1999ex provides first clear evidence for a link between the Ib and Ic classes and that there is a continuous spectroscopic sequence ranging from the He deficient SNe Ic to the SNe Ib which are characterized by strong optical He I lines.

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arXiv2001

CE-315 : A New Interacting Double-degenerate Binary Star

We present spectroscopic observations of object CE-315 revealing a blue continuum with strong emission lines. Most of the detected lines are identified with He I or He II in emission with a handful of faint lines of nitrogen. Notable is the complete absence of hydrogen lines. The He lines exhibit triple-peaked profiles with remakably broad widths, of about 2000 km/s (FWZP). The observations show that CE-315 is an interacting binary system with an orbital period of 65.1 +/- 0.7 minutes, and a mass ratio of 0.022. We conclude that the most likely scenario for this object is that of an accreting 0.77 solar mass white dwarf with a 0.017 solar mass helium white dwarf as mass donor.

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arXiv2000

A nearly symmetric double-image gravitational lens

We report the discovery of a new double-image gravitational lens resulting from our search for lenses in the southern sky. Radio source PMN J2004-1349 is composed of two compact components separated by 1.13 arcseconds in VLA, MERLIN and VLBA images. The components have a flux ratio of 1:1 at radio frequencies ranging from 5 GHz to 22 GHz. The I-band optical counterpart is also an equal double, with roughly the same separation and position angle as the radio double. Upon subtraction of the components from the I-band image, we identify a dim pattern of residuals as the lens galaxy. While the present observations are sufficient to establish that J2004-1349 is a gravitational lens, additional information will be necessary (such as the redshifts of the galaxy and quasar, and precise astrometry and photometry of the lens galaxy) before constructing detailed mass models.

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arXiv2000

A Close Separation Double Quasar Lensed by a Gas-Rich Galaxy

In the course of a Cycle 8 snapshot survey, we have discovered that the z=1.565 quasar HE 0512-3329 is a double with image separation 0.644", almost certainly due to gravitational lensing. The two components differ in brightness by only 0.4 magnitudes and a high signal-to-noise ground-based composite optical spectrum shows no trace of any stellar features at zero redshift, essentially ruling out the possibility that one of the two components is an ordinary Galactic star. The optical spectrum shows strong absorption features of MgII, MgI, FeII, FeI, and CaI, all at an identical intervening redshift of z=0.9313, probably due to the lensing object. The strength of the MgII and the presence of the other low ionization absorption features is strong evidence for a damped Lyman alpha system, likely the disk of a spiral galaxy. Point spread function fitting to remove the two quasar components from the STIS image leads to a tentative detection of a third object which may be the nucleus of the lensing galaxy. The brighter component is significantly redder than the fainter, due to either differential extinction or microlensing.

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