- 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.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/706/1484
- Title:
- Photometry and spectroscopy in IC 2391
- Short Name:
- J/ApJ/706/1484
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the stellar and substellar mass function (MF) of the open cluster IC 2391, plus its radial dependence, and use this to put constraints on the formation mechanism of brown dwarfs (BDs). Our multi-band optical and infrared photometric survey with spectroscopic follow-up covers 11deg^2^, making it the largest survey of this cluster to date. From our preliminary spectroscopic follow-up, to confirm BD status and cluster membership, we find that all candidates are M dwarfs (in either the field or the cluster), demonstrating the efficiency of our photometric selection method in avoiding contaminants (e.g., red giants). About half of our photometric candidates for which we have spectra are spectroscopically confirmed as cluster members; two are new spectroscopically confirmed BD members of IC 2391.
- ID:
- ivo://CDS.VizieR/J/AJ/144/125
- Title:
- Photometry and spectroscopy of Markarian 266
- Short Name:
- J/AJ/144/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of observations with the Spitzer, Hubble, GALEX, Chandra, and XMM-Newton space telescopes are presented for the luminous infrared galaxy (LIRG) merger Markarian 266. The SW (Seyfert 2) and NE (LINER) nuclei reside in galaxies with Hubble types SBb (pec) and S0/a (pec), respectively. Both companions are more luminous than L* galaxies and they are inferred to each contain a {approx}2.5x10^8^M_{sun}_ black hole. Although the nuclei have an observed hard X-ray flux ratio of f_X_(NE)/f_X_(SW)=6.4, Mrk 266 SW is likely the primary source of a bright Fe K{alpha} line detected from the system, consistent with the reflection-dominated X-ray spectrum of a heavily obscured active galactic nucleus (AGN). Optical knots embedded in an arc with aligned radio continuum radiation, combined with luminous H_2_line emission, provide evidence for a radiative bow shock in an AGN-driven outflow surrounding the NE nucleus. A soft X-ray emission feature modeled as shock-heated plasma with T~10^7^K is cospatial with radio continuum emission between the galaxies. Mid-infrared diagnostics provide mixed results, but overall suggest a composite system with roughly equal contributions of AGN and starburst radiation powering the bolometric luminosity. Approximately 120 star clusters have been detected, with most having estimated ages less than 50Myr. Detection of 24{mu}m emission aligned with soft X-rays, radio continuum, and ionized gas emission extending ~34" (20kpc) north of the galaxies is interpreted as ~2x10^7^M_{sun}_ of dust entrained in an outflowing superwind. At optical wavelengths this Northern Loop region is resolved into a fragmented morphology indicative of Rayleigh-Taylor instabilities in an expanding shell of ionized gas. Mrk 266 demonstrates that the dust "blow-out" phase can begin in a LIRG well before the galaxies fully coalesce during a subsequent ultraluminous infrared galaxy (ULIRG) phase, and rapid gas consumption in luminous dual AGNs with kiloparsec-scale separations early in the merger process may explain the paucity of detected binary QSOs (with parsec-scale orbital separations) in spectroscopic surveys. An evolutionary sequence is proposed representing a progression from dual to binary AGNs, accompanied by an increase in observed L_x_/L_ir_ ratios by over two orders of magnitude.
- ID:
- ivo://CDS.VizieR/J/ApJ/661/750
- Title:
- Photometry and spectroscopy of MS 1054-03 members
- Short Name:
- J/ApJ/661/750
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using a magnitude-limited, spectroscopic survey of the X-ray-luminous galaxy cluster MS 1054-03, we isolate 153 cluster galaxies and measure MS 1054's redshift and velocity dispersion to be z=0.8307+/-0.0004 and {sigma}_z_=1156+/-82km/s. The absorption-line, post-starburst ("E+A"), and emission-line galaxies, respectively, make up 63%+/-7%, 15%+/-4%, and 23%+/-4% of the cluster population. With photometry from HST ACS, we find that the absorption-line members define an exceptionally tight red sequence over a span of ~3.5mag in i775: their intrinsic scatter in (V606-i775) color is only 0.048+/-0.008, corresponding to a (U-B)z scatter of 0.041.
- ID:
- ivo://CDS.VizieR/J/AJ/150/200
- Title:
- Photometry and spectroscopy of stars in Cz 30
- Short Name:
- J/AJ/150/200
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new photometric and spectroscopic data of the old open cluster Czernik 30. Wide field BVI photometry allows us to correct for the high field contamination by statistical subtraction to produce a color-magnitude diagram (CMD) that clearly reveals the cluster sequence. From spectra of stars in the cluster field obtained with the Hydra spectrograph on the Wisconsin-Indiana-Yale-NOAO 3.5m telescope we determine a mean cluster velocity of +79.9+/-1.5km/s and provide membership information that helps further define the cluster giant branch and red clump. Stellar abundances for the brighter giants in the cluster indicate a mean metallicity of [Fe/H]=-0.2+/-0.15. Fitting theoretical isochrones to the CMD we determine the following properties of Czernik 30: age=2.8+/-0.3Gyr, (m-M)_v_=14.8+/-0.1, E(B-V)=0.24+/-0.06, and E(V-I)=0.36+/-0.04. Czernik 30 is an old, sub-solar metallicity cluster located at a Galactocentric radius of R_gc_~13.3kpc. Given its age and position just beyond the transition to a flat abundance gradient seen in the open cluster population, Czernik 30 provides an interesting target for future observations.
- ID:
- ivo://CDS.VizieR/J/AJ/156/37
- Title:
- Photometry & Li abund. of cool dwarfs in M35
- Short Name:
- J/AJ/156/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hydra spectra of 85 G-K dwarfs in the young cluster M35 near the Li 6708 {AA} line region are analyzed. From velocities and Gaia astrometry, 78 are likely single-star members that, combined with previous work, produce 108 members with T_eff_ ranging from 6150 to 4000 K as defined by multicolor, broadband photometry, E(B-V)=0.20, and [Fe/H]=-0.15, though there are indications the metallicity may be closer to solar. The Lithium abundance A(Li) follows a well-delineated decline from 3.15 for the hottest stars to upper limits =<1.0 among the coolest dwarfs. Contrary to earlier work, M35 includes single stars at systematically higher A(Li) than the mean cluster relation. This subset exhibits higher V_ROT_ than the more Li-depleted sample and, from photometric rotation periods, is dominated by stars classed as convective (C); all others are interface (I) stars. The cool, high-Li rapid rotators (RRs) are consistent with models that simultaneously consider rapid rotation and radius inflation; RRs hotter than the Sun exhibit excess Li depletion, as predicted by the models. The A(Li) distribution with color and rotation period, when compared to the Hyades/Praesepe and the Pleiades, is consistent with gyrochronological analysis placing M35's age between the older M34 and younger Pleiades. However, the Pleiades display a more excessive range in A(Li) and rotation period than M35 on the low-Li, slow-rotation side of the distribution, with supposedly younger stars at a given T_eff_ in the Pleiades spinning slower, with A(Li) reduced by more than a factor of four compared to M35.
- ID:
- ivo://CDS.VizieR/J/A+A/485/657
- Title:
- Physical parameters of Wolf-Rayet galaxies
- Short Name:
- J/A+A/485/657
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The availability of large spectroscopic datasets has opened up the possibility of constructing large samples of rare objects in a systematic manner. The goal of this study is to analyse the properties of galaxies showing Wolf-Rayet features in their optical spectrum using spectra from the Sloan Digital Sky Survey Release 6. With this unprecedentedly large sample we aim to constrain the properties of the Wolf-Rayet phase and its impact on the surrounding interstellar medium. We carried out very careful continuum subtraction on all galaxies with equivalent widths of H{beta}>2{AA} in emission and identify Wolf-Rayet features using a mixture of automatic and visual classification. We combined this with spectroscopic and photometric information from the SDSS and derive metal abundances using a number of methods.
- ID:
- ivo://CDS.VizieR/J/A+A/495/53
- Title:
- Physical properties of VVDS galaxies
- Short Name:
- J/A+A/495/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We want to derive the mass-metallicity relation of star-forming galaxies up to z~0.9, using data from the VIMOS VLT Deep Survey. The mass-metallicity relation is commonly understood as the relation between the stellar mass and the gas-phase oxygen abundance. Automatic measurement of emission-line fluxes and equivalent widths have been performed on the full spectroscopic sample of the VIMOS VLT Deep Survey. This sample is divided into two sub-samples depending on the apparent magnitude selection: wide (I_AB_<22.5) and deep (I_AB_<24). These two samples span two different ranges of stellar masses. Emission-line galaxies have been separated into star-forming galaxies and active galactic nuclei using emission line ratios. For the star-forming galaxies the emission line ratios have also been used to estimate gas-phase oxygen abundance, using empirical calibrations renormalized in order to give consistent results at low and high redshifts. The stellar masses have been estimated by fitting the whole spectral energy distributions with a set of stellar population synthesis models.
- ID:
- ivo://CDS.VizieR/J/AJ/141/137
- Title:
- Pittsburgh SDSS Mg II QSO catalog
- Short Name:
- J/AJ/141/137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of intervening Mg II quasar absorption-line systems in the redshift interval 0.36<=z<=2.28. The catalog was built from Sloan Digital Sky Survey Data Release Four (SDSS DR4, Cat. II/267) quasar spectra. Currently, the catalog contains ~17000 measured Mg II doublets. We also present data on the ~44600 quasar spectra which were searched to construct the catalog, including redshift and magnitude information, continuum-normalized spectra, and corresponding arrays of redshift-dependent minimum rest equivalent widths detectable at our confidence threshold. The catalog is available online. A careful second search of 500 random spectra indicated that, for every 100 spectra searched, approximately one significant Mg II system was accidentally rejected. Current plans to expand the catalog beyond DR4 quasars are discussed. Many Mg II absorbers are known to be associated with galaxies. Therefore, the combination of large size and well understood statistics makes this catalog ideal for precision studies of the low-ionization and neutral gas regions associated with galaxies at low to moderate redshift. An analysis of the statistics of Mg II absorbers using this catalog will be presented in a subsequent paper.
- ID:
- ivo://CDS.VizieR/J/ApJ/676/262
- Title:
- PKS1302-102 intergalactic absorption system
- Short Name:
- J/ApJ/676/262
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed analysis of the intergalactic metal-line absorption systems in the archival HST STIS and FUSE ultraviolet spectra of the low-redshift quasar PKS 1302-102 (z_QSO_=0.2784). We supplement the archive data with CLOUDY ionization models and a survey of galaxies in the quasar field.
