- ID:
- ivo://CDS.VizieR/J/ApJ/878/92
- Title:
- Rotation measures in radio source pairs
- Short Name:
- J/ApJ/878/92
- Date:
- 03 Mar 2022 08:14:01
- Publisher:
- CDS
- Description:
- Faraday rotation measures (RMs) of extragalactic radio sources provide information on line-of-sight magnetic fields, including contributions from our Galaxy, source environments, and the intergalactic medium (IGM). Looking at differences in RMs, {Delta}RM, between adjacent sources on the sky can help isolate these different components. In this work, we classify adjacent polarized sources in the NRAO VLA Sky Survey (NVSS) as random or physical pairs. We recompute and correct the uncertainties in the NVSS RM catalog, since these were significantly overestimated. Our sample contains 317 physical and 5111 random pairs, all with Galactic latitudes |b|>=20{deg}, polarization fractions >=2%, and angular separations between 1.5' and 20'. We find an rms {Delta}RM of 14.9+/-0.4 and 4.6+/-1.1rad/m^2^ for the random and physical pairs, respectively. This means that polarized extragalactic sources that are close on the sky but at different redshifts have larger differences in RM than two components of one source. This difference of ~10rad/m^2^ is significant at 5{sigma} and persists in different data subsamples. While there have been other statistical studies of {Delta}RM between adjacent polarized sources, this is the first unambiguous demonstration that some of this RM difference must be extragalactic, thereby providing a firm upper limit on the RM contribution of the IGM. If the {Delta}RMs originate local to the sources, then the local magnetic field difference between random sources is a factor of 2 larger than that between components of one source. Alternatively, attributing the difference in {Delta}RMs to the intervening IGM yields an upper limit on the IGM magnetic field strength of 40nG.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/898/102
- Title:
- Rotation velocity & dynamical mass of gal. from HI sp.
- Short Name:
- J/ApJ/898/102
- Date:
- 21 Mar 2022 08:49:45
- Publisher:
- CDS
- Description:
- The integrated 21cm HI emission profile of a galaxy encodes valuable information on the kinematics, spatial distribution, and dynamical state of its cold interstellar medium. The line width, in particular, reflects the rotation velocity of the galaxy, which, in combination with a size scale, can be used to constrain the dynamical mass of the system. We introduce a new method based on the concept of the curve of growth to derive a set of robust parameters to characterize the line width, asymmetry, and concentration of the integrated HI spectra. We use mock spectra to evaluate the performance of our method, to estimate realistic systematic uncertainties for the proposed parameters, and to correct the line widths for the effects of instrumental resolution and turbulence broadening. Using a large sample of nearby galaxies with available spatially resolved kinematics, we demonstrate that the newly defined line widths can predict the rotational velocities of galaxies to within an accuracy of <~30km/s. We use the calibrated line widths, in conjunction with the empirical relation between the size and mass of HI disks, to formulate a prescription for estimating the dynamical mass within the HI-emitting region of gas-rich galaxies. Our formalism yields dynamical masses accurate to ~0.3dex based solely on quantities that can be derived efficiently and robustly from current and future extragalactic HI surveys. We further extend the dynamical mass calibration to the scale of the dark matter halo.
- ID:
- ivo://CDS.VizieR/J/ApJ/835/104
- Title:
- SAMI Galaxy Survey: rotators classification
- Short Name:
- J/ApJ/835/104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent cosmological hydrodynamical simulations suggest that integral field spectroscopy can connect the high-order stellar kinematic moments h_3_ (~skewness) and h_4_ (~kurtosis) in galaxies to their cosmological assembly history. Here, we assess these results by measuring the stellar kinematics on a sample of 315 galaxies, without a morphological selection, using two-dimensional integral field data from the SAMI Galaxy Survey. Proxies for the spin parameter ({lambda}R_e_) and ellipticity ({epsilon}_e_) are used to separate fast and slow rotators; there exists a good correspondence to regular and non-regular rotators, respectively, as also seen in earlier studies. We confirm that regular rotators show a strong h_3_ versus V/{sigma} anti-correlation, whereas quasi-regular and non-regular rotators show a more vertical relation in h_3_ and V/{sigma}. Motivated by recent cosmological simulations, we develop an alternative approach to kinematically classify galaxies from their individual h_3_ versus V/{sigma} signatures. Within the SAMI Galaxy Survey, we identify five classes of high-order stellar kinematic signatures using Gaussian mixture models. Class 1 corresponds to slow rotators, whereas Classes 2-5 correspond to fast rotators. We find that galaxies with similar {lambda}R_e_-{epsilon}_e_ values can show distinctly different h_3_-V/{sigma} signatures. Class 5 objects are previously unidentified fast rotators that show a weak h_3_ versus V/{sigma} anti-correlation. From simulations, these objects are predicted to be disk-less galaxies formed by gas-poor mergers. From morphological examination, however, there is evidence for large stellar disks. Instead, Class 5 objects are more likely disturbed galaxies, have counter-rotating bulges, or bars in edge-on galaxies. Finally, we interpret the strong anti-correlation in h_3_ versus V/{sigma} as evidence for disks in most fast rotators, suggesting a dearth of gas-poor mergers among fast rotators.
- ID:
- ivo://CDS.VizieR/J/ApJ/635/243
- Title:
- Sample of GOODS/CDFS early-type galaxies
- Short Name:
- J/ApJ/635/243
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the evolution of field early-type galaxies in a sample extracted from the ACS images of the southern GOODS field. The galaxies are selected by means of a nonparametric analysis, followed by visual inspection of the candidates with a concentrated surface brightness distribution. We furthermore exclude from the final sample those galaxies that are not consistent with an evolution into the Kormendy relation between surface brightness and size that is observed for z=0 ellipticals. The final set, which comprises 249 galaxies with a median redshift z_m_=0.71, represents a sample of early-type systems not selected with respect to color, with similar scaling relations as those of bona fide elliptical galaxies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/476/4725
- Title:
- SC4K catalogue of candidate LAEs
- Short Name:
- J/MNRAS/476/4725
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present and explore deep narrow- and medium-band data obtained with the Subaru and the Isaac Newton Telescopes in the ~2deg^2^ COSMOS field. We use these data as an extremely wide, low-resolution (R~20-80) Integral Field Unit survey to slice through the COSMOS field and obtain a large sample of ~4000 Ly{alpha} emitters (LAEs) from z~2 to 6 in 16 redshift slices (SC4K). We present new Ly {alpha} luminosity functions (LFs) covering a comoving volume of ~10^8^Mpc^3^. SC4K extensively complements ultradeep surveys, jointly covering over 4dex in Ly{alpha} luminosity and revealing a global (2.5<z<6) synergy LF with {alpha}=-1.93^+0.12^_-0.12_, log_10_{Phi}^*^_Ly{alpha}_=-3.45^+0.22^_-0.29_Mpc^-3^, and log_10_L^*^_Ly{alpha}_=42.93^+0.15^_-0.11_erg/s. The Schechter component of the Ly{alpha} LF reveals a factor ~5 rise in L^*^_Ly{alpha}_ and a ~7 x decline in {Phi}^*^_Ly{alpha}_ from z~2 to 6. The data reveal an extra power-law (or Schechter) component above L_Ly{alpha}_~=10^43.3^erg/s at z~2.2-3.5 and we show that it is partially driven by X-ray and radio active galactic nucleus (AGN), as their Ly{alpha} LF resembles the excess. The power-law component vanishes and/or is below our detection limits above z>3.5, likely linked with the evolution of the AGN population. The Ly {alpha} luminosity density rises by a factor ~2 from z~2 to 3 but is then found to be roughly constant (1.1^+0.2^_-0.2_x10^40^erg/s/Mpc^3^) to z~6, despite the ~0.7 dex drop in ultraviolet (UV) luminosity density. The Ly{alpha}/UV luminosity density ratio rises from 4+/-1 per cent to 30+/-6 per cent from z~2.2 to 6. Our results imply a rise of a factor of ~=2 in the global ionization efficiency ({xi}_ion_) and a factor ~=4+/-1 in the Ly{alpha} escape fraction from z~2 to 6, hinting for evolution in both the typical burstiness/stellar populations and even more so in the typical interstellar medium conditions allowing Ly{alpha} photons to escape.
- ID:
- ivo://CDS.VizieR/J/ApJ/820/82
- Title:
- S2CLS: multiwavelength counterparts to SMGs
- Short Name:
- J/ApJ/820/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multiwavelength identifications for the counterparts of 1088 submillimeter sources detected at 850{mu}m in the SCUBA-2 Cosmology Legacy Survey (S2CLS) study of the UKIRT Infrared Deep Sky Survey-Ultra-Deep Survey (UDS) field. By utilizing an Atacama Large Millimeter Array (ALMA) pilot study on a subset of our bright SCUBA-2 sample as a training set, along with the deep optical-near-infrared (OIR) data available in this field, we develop a novel technique, Optical-IR Triple Color (OIRTC), using z-K, K-[3.6], [3.6]-[4.5] colors to select the candidate submillimeter galaxy (SMG) counterparts. By combining radio identification and the OIRTC technique, we find counterpart candidates for 80% of the Class = 1 >=4{sigma} SCUBA-2 sample, defined as those that are covered by both radio and OIR imaging and the base sample for our scientific analyses. Based on the ALMA training set, we expect the accuracy of these identifications to be 82%+/-20%, with a completeness of 69%+/-16%, essentially as accurate as the traditional p-value technique but with higher completeness. We find that the fraction of SCUBA-2 sources having candidate counterparts is lower for fainter 850{mu}m sources, and we argue that for follow-up observations sensitive to SMGs with S_850_>~1mJy across the whole ALMA beam, the fraction with multiple counterparts is likely to be >40% for SCUBA-2 sources at S_850_>~4mJy. We find that the photometric redshift distribution for the SMGs is well fit by a lognormal distribution, with a median redshift of z=2.3+/-0.1. After accounting for the sources without any radio and/or OIRTC counterpart, we estimate the median redshift to be z=2.6+/-0.1 for SMGs with S_850_>1mJy. We also use this new large sample to study the clustering of SMGs and the far-infrared properties of the unidentified submillimeter sources by stacking their Herschel SPIRE far-infrared emission.
- ID:
- ivo://CDS.VizieR/J/ApJ/784/9
- Title:
- SCUBA-2 high-redshift galaxies sample
- Short Name:
- J/ApJ/784/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the James Clerk Maxwell Telescope's SCUBA-2 camera to image a 400 arcmin^2^ area surrounding the GOODS-N field. The 850 {mu}m rms noise ranges from a value of 0.49 mJy in the central region to 3.5 mJy at the outside edge. From these data, we construct an 850 {mu}m source catalog to 2 mJy containing 49 sources detected above the 4{sigma} level. We use an ultradeep (11.5 {mu}Jy at 5{sigma}) 1.4 GHz image obtained with the Karl G. Jansky Very Large Array together with observations made with the Submillimeter Array to identify counterparts to the submillimeter galaxies. For most cases of multiple radio counterparts, we can identify the correct counterpart from new and existing Submillimeter Array data. We have spectroscopic redshifts for 62% of the radio sources in the 9' radius highest sensitivity region (556/894) and 67% of the radio sources in the GOODS-N region (367/543). We supplement these with a modest number of additional photometric redshifts in the GOODS-N region (30). We measure millimetric redshifts from the radio to submillimeter flux ratios for the unidentified submillimeter sample, assuming an Arp 220 spectral energy distribution. We find a radio-flux-dependent K-z relation for the radio sources, which we use to estimate redshifts for the remaining radio sources. We determine the star formation rates (SFRs) of the submillimeter sources based on their radio powers and their submillimeter fluxes and find that they agree well. The radio data are deep enough to detect star-forming galaxies with SFRs>2000 M_{sun}_/yr to z~6. We find galaxies with SFRs up to ~6000 M_{sun}_/yr over the redshift range z=1.5-6, but we see evidence for a turn-down in the SFR distribution function above 2000 M_{sun}_/yr.
- ID:
- ivo://CDS.VizieR/J/ApJ/832/78
- Title:
- SCUBA-2 & LABOCA obs. of HATLAS ultrared galaxies
- Short Name:
- J/ApJ/832/78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Until recently, only a handful of dusty, star-forming galaxies (DSFGs) were known at z>4, most of them significantly amplified by gravitational lensing. Here, we have increased the number of such DSFGs substantially, selecting galaxies from the uniquely wide 250, 350, and 500{mu}m Herschel-ATLAS imaging survey on the basis of their extremely red far-infrared colors and faint 350 and 500{mu}m flux densities, based on which, they are expected to be largely unlensed, luminous, rare, and very distant. The addition of ground-based continuum photometry at longer wavelengths from the James Clerk Maxwell Telescope and the Atacama Pathfinder Experiment allows us to identify the dust peak in their spectral energy distributions (SEDs), with which we can better constrain their redshifts. We select the SED templates that are best able to determine photometric redshifts using a sample of 69 high-redshift, lensed DSFGs, then perform checks to assess the impact of the CMB on our technique, and to quantify the systematic uncertainty associated with our photometric redshifts, {sigma}=0.14(1+z), using a sample of 25 galaxies with spectroscopic redshifts, each consistent with our color selection. For Herschel-selected ultrared galaxies with typical colors of S_500_/S_250_~2.2 and S_500_/S_350_~1.3 and flux densities, S500~50mJy, we determine a median redshift, z_phot_=3.66, an interquartile redshift range, 3.30-4.27, with a median rest-frame 8-1000{mu}m luminosity, L_IR_, of 1.3x10^13^L_{sun}_. A third of the galaxies lie at z>4, suggesting a space density, {rho}_z>4_, of ~6x10^-7^Mpc^-3^. Our sample contains the most luminous known star-forming galaxies, and the most overdense cluster of starbursting proto-ellipticals found to date.
- ID:
- ivo://CDS.VizieR/J/ApJ/657/738
- Title:
- SDF galaxies multi-photometry
- Short Name:
- J/ApJ/657/738
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- SDF (Subaru Deep Field) line-emitting galaxies in four narrow-band filters at low and intermediate redshifts are presented. Broadband colors, follow-up optical spectroscopy, and multiple NB filters are used to distinguish H{alpha}, [OII], and [OIII] emitters at z=0.07-1.47 to construct their LFs. These LFs are derived down to faint magnitudes, allowing for an accurate determination of the faint-end slope. With a large (N~200) sample for each redshift interval, a Schechter profile is fitted to each LF.
- ID:
- ivo://CDS.VizieR/J/ApJ/732/110
- Title:
- SDSS 2175{AA} extinction bump candidates
- Short Name:
- J/ApJ/732/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report detections of 39 2175{AA} dust extinction bump candidates associated with strong MgII absorption lines at z~1-1.8 on quasar spectra in Sloan Digital Sky Survey (SDSS) DR3. These strong MgII absorption line systems are detected among 2951 strong MgII absorbers with a rest equivalent width W_r_{lambda}2796>1.0{AA} at 1.0<z<1.86, which is part of a full sample of 7421 strong MgII absorbers compiled by Prochter et al. (2006, Cat. J/ApJ/639/766). The redshift range of the absorbers is chosen to allow the 2175{AA} extinction features to be completely covered within the SDSS spectrograph operation wavelength range. An upper limit of the background quasar emission redshift at z=2.1 is set to prevent the Ly{alpha} forest lines from contaminating the sensitive spectral region for the 2175{AA} bump measurements. A total of 12 absorbers are detected with 2175{AA} bumps at a 5{sigma} level of statistical significance, 10 are detected at a 4{sigma} level, and 17 are detected at a 3{sigma} level. Most of the candidate bumps in this work are similar to the relatively weak 2175{AA} bumps observed in the Large Magellanic Cloud LMC2 supershell rather than the strong ones observed in the Milky Way.