735 research outputs found

    Vigorous star formation in a bulge-dominated ERO at z = 1.34

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    We present near-IR spectroscopy of three Extremely Red Objects (EROs) using the OHS/CISCO spectrograph at Subaru telescope. One target exhibits a strong emission line which we identify as H-alpha at z = 1.34. Using new and existing ground-based optical and near-IR imaging, and archival HST imaging, we argue that this target is essentially an elliptical galaxy, with an old stellar population of around 4E11 solar masses, but having a dust-enshrouded star-forming component with a SFR of some 50--100 solar masses per yr. There is no evidence that the galaxy contains an AGN. Analysis of a further two targets, which do not exhibit any features in our near-IR spectra, suggests that one is a quiescent galaxy in the redshift range 1.2 < z < 1.6, but that the other cannot be conclusively categorised as either star-forming or quiescent. Even though our first target has many of the properties of an old elliptical, the ongoing star formation means that it cannot have formed_all_ of its stellar population at high redshift. While we cannot infer any robust values for the star formation rate in ellipticals at z > 1 from this one object, we argue that the presence of an object with such a high SFR in such a small sample suggests that a non-negligible fraction of the elliptical galaxy population may have formed a component of their stellar population at redshifts z ~ 1--2. We suggest that this is evidence for ongoing star formation in the history of elliptical galaxies.Comment: Accepted by MNRAS 1 April 2005. Ten pages, six figure

    Deep optical imaging of the field of PC1643+4631A&B, II: Estimating the colours and redshifts of faint galaxies

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    In an investigation of the cause of the cosmic microwave background decrement in the field of the z = 3.8 quasar pair PC1643+4631, we have carried out a study to photometrically estimate the redshifts of galaxies in deep multi-colour optical images of the field taken with the WHT. To examine the possibility that a massive cluster of galaxies lies in the field, we have attempted to recover simulated galaxies with intrinsic colours matching those of the model galaxies used in the photometric redshift estimation. We find that when such model galaxies are added to our images, there is considerable scatter of the recovered galaxy redshifts away from the model value; this scatter is larger than that expected from photometric errors and is the result of confusion, simply due to ground-based seeing, between objects in the field. We have also compared the likely efficiency of the photometric redshift technique against the colour criteria used to select z>3 galaxies via the strong colour signature of the Lyman-limit break. We find that these techniques may significantly underestimate the true surface density of z>3, due to confusion between the high-redshift galaxies and other objects near the line of sight. We argue that the actual surface density of z=3 galaxies may be as much as 6 times greater than that estimated by previous ground-based studies, and note that this conclusion is consistent with the surface density of high-redshift objects found in the HDF. Finally, we conclude that all ground-based deep field surveys are inevitably affected by confusion, and note that reducing the effective seeing in ground-based images will be of paramount importance in observing the distant universe.Comment: 18 pages, 60 figures, submitted to MNRAS, 2 large figure avaliable at ftp://ftp.mrao.cam.ac.uk:/pub/PC1643/paper2.figure50.eps and ftp://ftp.mrao.cam.ac.uk:/pub/PC1643/paper2.figure51.ep

    Deep optical imaging of the field of PC1643+4631A&B, I: Spatial distributions and the counts of faint galaxies

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    We present deep optical images of the PC1643+4631 field obtained at the WHT. This field contains two quasars at redshifts z=3.79 & 3.83 and a cosmic microwave background (CMB) decrement detected with the Ryle Telescope. The images are in U,G,V,R and I filters, and are complete to 25th magnitude in R and G and to 25.5 in U. The isophotal galaxy counts are consistent with the results of Metcalde et al. (1996), Hogg et al. (1997), and others. We find an excess of robust high-redshift Ly-break galaxy candidates with 25.0<R<25.5 compared with the mean number found in the fields studied by Steidel et al. -we expect 7 but find 16 - but we do not find that the galaxies are concentrated in the direction of the CMB decrement. However, we are still not sure of the distance to the system causing the CMB decrement. We have also used our images to compare the commonly used object-finding algorithms of FOCAS and SExtractor: we find FOCAS the more efficient at detecting faint objects and the better at dealing with composite objects, whereas SExtractor's morphological classification is more reliable, especially for faint objects near the resolution limit. More generally, we have also compared the flux lost using isophotal apertures on a real image with that on a noise-only image: recovery of artificial galaxies from the noise-only image significantly overestimates the flux lost from the galaxies, and we find that the corrections made using this technique suffer a systematic error of some 0.4 magnitudes.Comment: 17 pages, 40 figures, submitted to MNRAS, 1 large figure avaliable at ftp://ftp.mrao.cam.ac.uk:/pub/PC1643/paper1.figure18.p

    a meta-analysis of correlations

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    A number of prominent theories have linked tendencies to mimick others' facial movements to empathy and facial emotion recognition, but evidence for such links is uneven. We conducted a meta-analysis of correlations of facial mimicry with empathy and facial emotion recognition skills. Other factors were also examined for moderating influence, e.g. facets of empathy measured, facial muscles recorded, and facial emotions being mimicked. Summary effects were estimated with a random-effects model and a meta-regression analysis was used to identify factors moderating these effects. 162 effects from 28 studies were submitted. The summary effect size indicated a significant weak positive relationship between facial mimicry and empathy, but not facial emotion recognition. The moderator analysis revealed that stronger correlations between facial mimicry and empathy were observed for static vs. dynamic facial stimuli, and for implicit vs. explicit instances of facial emotion processing. No differences were seen between facial emotions, facial muscles, emotional and cognitive facets of empathy, or state and trait measures of empathy. The results support the claim that stronger facial mimicry responses are positively related to higher dispositions for empathy, but the weakness and variability of this effect suggest that this relationship is conditional on not-fully understood factors

    Optical Spectroscopy of Bright Fermi LAT Blazars

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    We report on HET and Palomar 5 m spectroscopy of recently identified Îł\gamma-ray blazars in the {\it Fermi} LAT Bright Source List. These data provide identifications for 10 newly discovered Îł\gamma-ray flat spectrum radio quasars (FSRQ) and six new BL Lacs plus improved spectroscopy for six additional BL Lacs. We substantially improve the identification completeness of the bright LAT blazars and give new redshifts and zz constraints, new estimates of the black hole masses and new measurements of the optical SED.Comment: 8 pages, 5 figures, 2 tables. Accepted for publication in Ap

    CGRaBS: An All-Sky Survey of Gamma-Ray Blazar Candidates

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    We describe a uniform all-sky survey of bright blazars, selected primarily by their flat radio spectra, that is designed to provide a large catalog of likely gamma-ray AGN. The defined sample has 1625 targets with radio and X-ray properties similar to those of the EGRET blazars, spread uniformly across the |b| > 10 deg sky. We also report progress toward optical characterization of the sample; of objects with known R < 23, 85% have been classified and 81% have measured redshifts. One goal of this program is to focus attention on the most interesting (e.g., high redshift, high luminosity, ...) sources for intensive multiwavelength study during the observations by the Large Area Telescope (LAT) on GLAST.Comment: 18 pages, 6 figures, 1 machine-readable table available at http://astro.stanford.edu/CGRaBS/ ; accepted for publication in ApJ

    Assessment of Trees Outside Forest (TOF) in Selected Makiling Subwatersheds

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    Trees outside Forest (TOF) are trees, shrubs, bushes including palms that are found in the Food and Agriculture Organization (FAO) other land classification that can be agricultural, urban, or non-agricultural/urban. TOF provide various services and functions that are neither well documented nor given enough attention, hence the need to identify and assess them in agriculture and urban areas outside Mt. Makiling. A SPOT satellite image (2010) covering the Cambantoc, Molawin-Dampalit, and Tigbi subwatersheds of Mt. Makiling was used in the supervised classification of forests, lakes, agriculture, and urban areas. Areas that qualify as other lands were extracted using the classified land types as guides in GIS vector format. Using Google Earth imagery, other lands were digitized and assessed following the FAO decision tree algorithm for TOF and field checking was conducted to validate the tree height in the TOF criteria. Based on the GIS and field assessment, Tigbi and Molawin-Dampalit were found to have TOF on urban land that are mostly fruit trees cultivated for food, landscaping while Cambantoc has TOF on agricultural land and TOF on non-agricultural/urban that are used as farm windbreaks. Findings suggested that TOF contributed to the tree canopy cover in Makiling subwatersheds. Assessment of TOF can be used to account for the ecosystem services it provides which complement those that come from forests and other wooded lands. FAO also recognizes the importance of TOF for local and national food security. TOF, especially fruit trees, are important source of food products for the people
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