- ID:
- ivo://CDS.VizieR/J/ApJ/728/23
- Title:
- GALEX UV-bright high-redshift quasars
- Short Name:
- J/ApJ/728/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the small population of high-redshift (z_em_>2.7) quasars detected by the Galaxy Evolution Explorer(GALEX), whose far-UV emission is not extinguished by intervening HI Lyman limit systems. We correlate almost all verified z_em_>2.7 quasars to the GALEX GR4 source catalog covering ~25000deg^2^, yielding 304 sources detected at signal-to-noise ratio (S/N)>3. However, ~50% of these are only detected in the GALEX NUV band, signaling the truncation of the FUV flux by low-redshift optically thick Lyman limit systems. We regard 52 quasars detected at S/N>3 to be most promising for Hubble Space Telescope follow-up, with an additional 114 quasars if we consider S/N>2 detections in the FUV. Combining the statistical properties of HI absorbers with the Sloan Digital Sky Survey (SDSS) quasar luminosity function, we predict a large all-sky population of ~200 quasars with z_em_>2.7 and i<~19 that should be detectable at the HeII edge at m_304_<21. However, SDSS provides just half of the NUV-bright quasars that should have been detected by SDSS and GALEX. With mock quasar photometry we revise the SDSS quasar selection function, finding that SDSS systematically misses quasars with blue u-g<~2 colors at 3<~z_em_<~3.5 due to overlap with the stellar locus in color space.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/173/643
- Title:
- GALEX UV photometry of M31 Globular Clusters
- Short Name:
- J/ApJS/173/643
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ultraviolet (UV) photometry of M31 globular clusters (GCs) found in 23 Galaxy Evolution Explorer (GALEX) images covering the entirety of M31. We detect 485 and 273 GCs (and GC candidates) in the near-ultraviolet (NUV) and far-ultraviolet (FUV), respectively. The UV properties of GCs have been analyzed using various combinations of UV-optical and optical-optical colors. Comparing M31 data with those of Galactic GCs in the UV with the aid of population models, we find that the age ranges of old GCs in M31 and the Galactic halo are similar. Three metal-rich ([Fe/H]>-1) GCs in M31 produce significant FUV flux making their FUV-V colors unusually blue for their metallicities. These are thought to be analogs of the two peculiar Galactic GCs, NGC 6388 and NGC 6441, with extended blue HB stars. We detect 12 (10) intermediate-age GC candidates in NUV (FUV) identified by previous spectroscopic observations. On the basis of comparing our UV photometry to population models, we suggest that some of spectroscopically identified intermediate-age GCs may not be truly intermediate in age, but rather older GCs that possess developed HB stars which contribute to enhanced UV flux as well as Balmer lines.
- ID:
- ivo://CDS.VizieR/J/ApJ/879/22
- Title:
- GALFA-HI search for local dwarf galaxies
- Short Name:
- J/ApJ/879/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In recent years, ultrafaint dwarf (UFD) galaxies have been found through systematic searches of large optical surveys. However, the existence of Leo T, a nearby gas-rich dwarf, suggests that there could be other nearby UFDs that are optically obscured but have gas detectable at nonoptical wavelengths. With this in mind, we perform a search of the full Galactic Arecibo L-band Feed Array HI (GALFA-HI) survey, a radio survey that covers one-third of the sky at velocities -650<V_LSR_<+650km/s, for neutral hydrogen sources. We are able to probe regions of the sky at lower Galactic latitudes and smaller |V_LSR_| compared to previous explorations. We use the Source Finding Application on GALFA-HI and select all sources with similar properties to Leo T and other local dwarf galaxies. We find 690 dwarf galaxy candidates, one of which is particularly promising and likely a new galaxy near the Galactic plane (b=-8{deg}) that is comparable in velocity width and HI-flux to other recently discovered local volume galaxies. We find we are sensitive to Leo T-like objects out to 1Mpc at velocities clear from background HI emission. We check each candidate's corresponding optical fields from Pan-STARRS and fit stars drawn from isochrones, but find no evidence of stellar populations. We thus find no other Leo T-like dwarfs within 500 kpc of the Milky Way in the one-third of the sky covered by the GALFA-HI footprint, and discuss our nondetection in a cosmological context.
- ID:
- ivo://CDS.VizieR/J/ApJS/172/615
- Title:
- GALFIT result for GEMS galaxies
- Short Name:
- J/ApJS/172/615
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the context of measuring the structures of intermediate-redshift galaxies with HST ACS surveys, we tune, test, and compare two widely used fitting codes (GALFIT and GIM2D) for fitting single-component Sersic models to both simulated and real galaxy data. Our study focuses on the GEMS survey (Rix et al., 2004ApJS..152..163R) with the sensitivity of typical HST survey data, and we include our final catalog of fit results for all 41495 objects detected in GEMS. Using simulations, we find that fitting accuracy depends sensitively on galaxy profile shape.
- ID:
- ivo://CDS.VizieR/J/other/SoSyR/50.344
- Title:
- Galilean moons & Jupiter positions
- Short Name:
- J/other/SoSyR/50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observational results are presented for Jupiter and its Galilean moons from the Normal Astrograph at Pulkovo Observatory in 2013-2015. The following data are obtained: 154 positions of the Galilean satellites and 47 calculated positions of Jupiter in the system of the UCAC4 (ICRS, J2000.0) catalogue; the differential coordinates of the satellites relative to one another are determined. The mean errors of the satellites normal places in right ascension and declination over the entire observational period are, respectively: (eps)RA=0.0065" and (eps)DE=0.0068", and their standard deviations are (sigm)RA=0.0804" and (sigm)DE=0.0845". The equatorial coordinates are compared with planetary and satellite motion theories. The average (O-C) residuals in the two coordinates relative to the motion theories are 0.05" or less. The best agreement with the observations is achieved by a combination of the EPM2011m and V. Lainey-V.2.0|V1.1 motion theories; the average (O-C) residuals are 0.03" or less. The (O-C) residuals for the features of the positions of Io and Ganymede are comparable with measurement errors. Jupiter's positions calculated from the observations of the satellites and their theoretical jovicentric coordinates are in good agreement with the motion theories. The (O-C) residuals for Jupiter's coordinates are, on average, 0.027" and -0.025" in the two coordinates.
6996. Galilean moons positions
- ID:
- ivo://CDS.VizieR/J/other/SoSyR/52.312
- Title:
- Galilean moons positions
- Short Name:
- J/other/SoSyR/52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of the Galilean moons observationals taken with Normal Astrograph of the Pulkovo Observatory in 2016-2017 are presented. 761 positions of the Galilean moons of Jupiter in the system of the Gaia DR1 catalog (ICRF, J2000.0) and 854 differential coordinates of the satellites relative to each other were obtained. The mean errors in the satellites' normal places and the corresponding root-mean-square deviations are (eps)RA=0.0020", (eps)DE=0.0027", (sigm)RA=0.0546", and (sigm)DE=0.0757". The equatorial coordinates of the moons are compared to the motion theories of planets and satellites. On average, the (O-C) residuals in the both coordinates relative to the motion theories are less than 0.031". The best agreement with observations is achieved by a combination of the EPM2015 and V. Lainey-V.2.0|V1.1 motion theories, which yields the average (O-C) residuals of approximately 0.02". Peculiarities in the behavior of the (O-C) residuals and error values in Ganymede have been noticed.
- ID:
- ivo://CDS.VizieR/J/A+A/427/371
- Title:
- Galilean satellites ephemerides
- Short Name:
- J/A+A/427/371
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new model of the four Galilean satellites Io, Europa, Ganymede and Callisto, able to deliver accurate ephemerides over a very long time span (several centuries). In the first paper (Lainey et al., 2004A&A...420.1171L) we gave the equations of the dynamical model. Here we present the fit of this model to the observations, covering more than one century starting from 1891. Our ephemerides, based on this first fit called L1, are available on the web page of the IMCCE at the URL http://www.imcce.fr/ephemeride_eng.html .
- ID:
- ivo://CDS.VizieR/J/other/SoSyR/49.383
- Title:
- Galilean satellites & Jupiter positions
- Short Name:
- J/other/SoSyR/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For observational period of 2009-2011 we have obtained 140 positions of Galilean satellites and 42 calculated positions of Jupiter in the system of UCAC4 catalogue (ICRS, J2000.0). Accuracy estimation gives error of mean position as 0.02-0.04". The resulting equatorial coordinates satellites were compared with the eight contemporary theories of the motion of planets and satellites. On average, the (O-C) residuals in both coordinates do not exceed 0.08" relative to all theories of motion. Comparison of the calculated equatorial coordinates of Jupiter (were obtained from observations of galilean satellites) with the INPOP10 theory of planetary motion has shown satisfactory results. The average deviations were obtained respectively (O-C)RA=0.040" and (O-C)DE=-0.053". This work was supported by the Program 22 of the Presidium of RAS and RFBR grant (12-02-00675-a).
- ID:
- ivo://CDS.VizieR/J/A+A/383/719
- Title:
- Galilean Satellites mutual events 2002-2003
- Short Name:
- J/A+A/383/719
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Mutual occultations and eclipses of the Galilean satellites of Jupiter will occur in 2002-2003. This paper provides predictions of these events as well as information useful for their observations. Such events are uncommon, since they occur only every 6 years when the Earth and the Sun pass through the common orbital plane of the Galilean satellites. Therefore, we encourage professional and amateur astronomers to join the networks of observers in order to get as many observations as possible. Data on the predictions of the events are available on the web server of the Institut de Mecanique Celeste et de Calcul de Ephemerides (IMCCE) ( http://www.bdl.fr ).
- ID:
- ivo://CDS.VizieR/J/A+A/314/312
- Title:
- Galilean satellites mutual events in 1997
- Short Name:
- J/A+A/314/312
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper provides the predictions of the mutual phenomena of the Galilean satellites which will occur in 1997. Past experiences have shown the interest of the observation of such events very rare, since they occur only every 6 years when the Earth and the Sun pass through the common orbital plane of the Galilean satellites.