- ID:
- ivo://CDS.VizieR/J/ApJ/862/12
- Title:
- Photometric Redshift Catalog (SCUSS, SDSS, WISE)
- Short Name:
- J/ApJ/862/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We publish a photometric redshift catalog based on imaging data of the South Galactic Cap u-band Sky Survey, Sloan Digital Sky Survey (SDSS), and Wide-field Infrared Survey Explorer (WISE). A total of 7 photometric bands are used, ranging from near ultraviolet to near infrared. A local linear regression method is adopted to estimate the photometric redshift with a dedicated spectroscopic training set. The photometric redshift catalog contains about 23.1 million galaxies classified by SDSS. Using the training set with redshift up to 0.8 and r-band magnitude down to 22mag, we achieve an average bias of {Delta}z_norm_=0.000228, standard deviation of {sigma}({Delta}z_norm_)=0.019, and 3{sigma} outlier rate of about 4.2%. The bias is less than 0.01 at z<0.6 and goes up to about 0.05 at z~0.8. Compared with SDSS photometric redshifts, our redshift estimations are more accurate and have less bias.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/157/99
- Title:
- Photometric redshifts of emission-line galaxies
- Short Name:
- J/AJ/157/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Broadband photometric redshifts are routinely obtained for galaxies to estimate their distances. While effective for many uses, the common resolution in z of 0.01-0.02 is too coarse for detailed large-scale structure mapping, particularly in low-density volumes where the galaxy distribution is least understood. To map galaxies in these low-density volumes, and noting that the percentage of galaxies having emission tends to rise as number density decreases, we have designed a filter system to photometrically measure the redshifts of galaxies with emission. The system consists of two "ramp" filters that cover a common wavelength range with transmission curves sloping from blue to red and from red to blue respectively. This causes the intensity of the image through either filter to be a function of the wavelength of the emission line. A third filter with a bandpass to the side is used to measure and remove the continuum. We have obtained a set of such filters that are tuned for isolating H{alpha} in the redshift range of 3000-9000 km/s. Simulated photometry, applied to spectra of 197 emission-line galaxies from the SDSS, shows the accuracy of the method to be between 250 and 620 km/s, depending on line strength. Actual photometry of a sample of 16 active galaxies measured their redshifts with an accuracy of 573 km/s. This is approximately an order of magnitude more accurate than broadband photometric redshifts. We discuss the errors inherent in this method and present ways to modify the filter set to further improve accuracy.
- ID:
- ivo://CDS.VizieR/J/MNRAS/405/1089
- Title:
- Photometric scaling for L/S0 galaxies
- Short Name:
- J/MNRAS/405/1089
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric scaling relations are studied for S0 galaxies and compared with those obtained for spirals. New two-dimensional multi-component decompositions are presented for 122 early-type disc galaxies, using deep Ks-band images. Combining them with our previous decompositions, the final sample consists of 175 galaxies (Near-Infrared Survey of S0s, NIRS0S: 117 S0s + 22 S0/a and 36 Sa galaxies). As a comparison sample we use the Ohio State University Bright Spiral Galaxy Survey (OSUBSGS) of nearly 200 spirals, for which similar multi-component decompositions have previously been made by us.
- ID:
- ivo://CDS.VizieR/J/MNRAS/486/1377
- Title:
- Photometric SFR using machine learning
- Short Name:
- J/MNRAS/486/1377
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Star formation rates (SFRs) are crucial to constrain theories of galaxy formation and evolution. SFRs are usually estimated via spectroscopic observations requiring large amounts of telescope time. We explore an alternative approach based on the photometric estimation of global SFRs for large samples of galaxies, by using methods such as automatic parameter space optimisation, and supervised machine learning models. We demonstrate that, with such approach, accurate multiband photometry allows to estimate reliable SFRs. We also investigate how the use of photometric rather than spectroscopic redshifts, affects the accuracy of derived global SFRs. Finally, we provide a publicly available catalogue of SFRs for more than 27 million galaxies extracted from the Sloan Digital Sky Survey Data Release 7. The catalogue will be made available through the Vizier facility.
- ID:
- ivo://CDS.VizieR/J/AJ/158/175
- Title:
- Photometric & spectroscopic study of AF And in M31
- Short Name:
- J/AJ/158/175
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a photometric and spectroscopic analysis of the Hubble-Sandage variable star AF And in M31. The data have been taken under the Nainital Microlensing Survey during 1998-2002, and follow-up observations were carried out until 2011. During this period, photometric observations in Cousins R and I bands were obtained for 169 nights spanning about 5000 days. AF And showed a prominent outburst around 1999 mid-January, followed by a gradual decrease in brightness of about 1.5 mag in the next 3 yr with a declining rate of ~0.0015 mag/day, leading to a quiescent phase at the end of 2001. After lying low for about 9 yr, AF And again went through a secondary outburst phase in late 2010 with an amplitude of 0.44 mag, where it lasted for one year before fading back to its quiescent phase. Spectroscopic observations of AF And show prominent Balmer and He I emission lines along with the comparatively weaker Fe II and [Fe II] emissions. Asymmetric emission line profiles in its spectrum imply a mass-loss rate of about 2.2x10^-4^ M_{sun}_/yr through the stellar winds in the photosphere. Using spectral energy distribution fitting, we find a photospheric temperature of 33000+/-3000 K during the visual minimum. Using a weak P Cygni profile of the He I emission line, the wind terminal velocity for AF And is found to be around 280-300 km/s.
- ID:
- ivo://CDS.VizieR/J/AcA/58/23
- Title:
- Photometric survey for M33 stellar clusters
- Short Name:
- J/AcA/58/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 4780 extended sources from the outer field of M33. The catalog includes 73 previously identified clusters or planetary nebulae, 1153 likely background galaxies, and 3554 new candidate stellar clusters. The survey is based on deep ground-based images obtained with the MegaCam instrument on the CFHT telescope. We provide g'r'i' photometry for detected objects as well as estimates of the FWHM and ellipticity of their profiles. The sample includes 122 new, relatively bright, likely globular clusters. Follow-up observations of fainter candidates from our list may extend the faint-end of the observed luminosity function of globular clusters in M33 by up to 3 magnitudes. The catalog includes several cluster candidates located in the outskirts of the galaxy. These objects are promising targets for deep photometry with the HST. We present a color-magnitude diagram for one detected object, showing that it is an extended and low-surface-brightness old cluster located at an angular distance of 27' from the center of M33.
- ID:
- ivo://CDS.VizieR/J/ApJ/792/121
- Title:
- Photometric survey of planetary nebulae in M31
- Short Name:
- J/ApJ/792/121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We search the Hubble Space Telescope (HST) Advanced Camera for Surveys and Wide Field Camera 3 broadband imaging data from the Panchromatic Hubble Andromeda Treasury (PHAT) survey to identify detections of cataloged planetary nebulae (PNs). Of the 711 PNs currently in the literature within the PHAT footprint, we find 467 detected in the broadband. For these 467, we are able to refine their astrometric accuracy from ~0.3'' to 0.05''. Using the resolution of the HST, we are able to show that 152 objects currently in the catalogs are definitively not PNs, and we show that 32 objects thought to be extended in ground-based images are actually point-like and therefore good PN candidates. We also find one PN candidate that is marginally resolved. If this is a PN, it is up to 0.7 pc in diameter. With our new photometric data, we develop a method of measuring the level of excitation in individual PNs by comparing broadband and narrowband imaging and describe the effects of excitation on a PN's photometric signature. Using the photometric properties of the known PNs in the PHAT catalogs, we search for more PNs, but do not find any new candidates, suggesting that ground-based emission-line surveys are complete in the PHAT footprint to F475W =~ 24.
- ID:
- ivo://CDS.VizieR/J/A+A/448/893
- Title:
- Photometry and lines of (z~0.2-1.0) galaxies
- Short Name:
- J/A+A/448/893
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the spectrophotometric properties of a sample of 141 emission-line galaxies at redshifts in the range 0.2<z<1.0 with a peak around 0.2<=z<=0.4. The analysis is based on medium resolution (Rs=500-600), optical spectra obtained at VLT and Keck. The targets are mostly "Canada-France Redshift Survey" (<VII/225>) emission-line galaxies, with the addition of field galaxies randomly selected behind lensing clusters. We complement this sample with galaxy spectra from the "Gemini Deep Deep Survey" (<J/AJ/127/2455>) public data release. We have computed absolute magnitudes of the galaxies and measured the line fluxes and equivalent widths of the main emission/absorption lines. The last two have been measured after careful subtraction of the fitted stellar continuum using the platefit software originally developed for the SDSS and adapted to our data. We present a careful comparison of this software with the results of manual measurements.
- ID:
- ivo://CDS.VizieR/J/A+A/424/79
- Title:
- Photometry and Metallicity in ABCG 209 galaxies
- Short Name:
- J/A+A/424/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse the properties of galaxy populations in the rich Abell cluster ABCG 209 at redshift z~0.21, on the basis of spectral classification of 102 member galaxies. We take advantage of available structural parameters to study separately the properties of bulge-dominated and disk-dominated galaxies. The star formation histories of the cluster galaxy populations are investigated by using line strengths and the 4000{AA} break, through a comparison to stellar population synthesis models. The dynamical properties of different spectral classes are examined in order to infer the past merging history of ABCG 209. The cluster is characterized by the presence of two components: an old galaxy population, formed very early (z_f>~3.5), and a younger (z_f>~1.2) population of infalling galaxies. We find evidence of a merger with an infalling group of galaxies occurred 3.5-4.5Gyr ago. The correlation between the position of the young H_delta-strong galaxies and the X-ray flux shows that the hot intracluster medium triggered a starburst in this galaxy population ~3Gyr ago.
- ID:
- ivo://CDS.VizieR/J/AJ/150/31
- Title:
- Photometry and redshifts of galaxies in the UDF
- Short Name:
- J/AJ/150/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photometry and derived redshifts from up to eleven bandpasses for 9927 galaxies in the Hubble Ultra Deep field (UDF), covering an observed wavelength range from the near-ultraviolet (NUV) to the near-infrared (NIR) with Hubble Space Telescope observations. Our Wide Field Camera 3 (WFC3)/UV F225W, F275W, and F336W image mosaics from the ultra-violet UDF (UVUDF) imaging campaign are newly calibrated to correct for charge transfer inefficiency, and use new dark calibrations to minimize background gradients and pattern noise. Our NIR WFC3/IR image mosaics combine the imaging from the UDF09 and UDF12 campaigns with CANDELS data to provide NIR coverage for the entire UDF field of view. We use aperture-matched point-spread function corrected photometry to measure photometric redshifts in the UDF, sampling both the Lyman break and Balmer break of galaxies at z~0.8--3.4, and one of the breaks over the rest of the redshift range. Our comparison of these results with a compilation of robust spectroscopic redshifts shows an improvement in the galaxy photometric redshifts by a factor of two in scatter and a factor three in outlier fraction (OLF) over previous UDF catalogs. The inclusion of the new NUV data is responsible for a factor of two decrease in the OLF compared to redshifts determined from only the optical and NIR data, and improves the scatter at z<0.5 and at z>2. The panchromatic coverage of the UDF from the NUV through the NIR yields robust photometric redshifts of the UDF, with the lowest OLF available.
