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25481. YZ Ceti CARMENES and HARPS radial velocity curve
ID:
ivo://CDS.VizieR/J/A+A/636/A119
Title:
YZ Ceti CARMENES and HARPS radial velocity curve
Short Name:
J/A+A/636/A119
Date:
25 Oct 2021 00:44:17
Publisher:
CDS
Description:
The nearby ultra-compact multiplanetary system YZ Ceti consists of at least three planets, and a fourth tentative signal. The orbital period of each planet is the subject of discussion in the literature due to strong aliasing in the radial velocity data. The stellar activity of this M dwarf also hampers significantly the derivation of the planetary parameters. With an additional 229 radial velocity measurements obtained since the discovery publication, we reanalyze the YZ Ceti system and resolve the alias issues. We use model comparison in the framework of Bayesian statistics and periodogram simulations based on a method by Dawson and Fabrycky to resolve the aliases. We discuss additional signals in the RV data, and derive the planetary parameters by simultaneously modeling the stellar activity with a Gaussian process regression model. To constrain the planetary parameters further we apply a stability analysis on our ensemble of Keplerian fits. We find no evidence for a fourth possible companion. We resolve the aliases: the three planets orbit the star with periods of 2.02d, 3.06d, and 4.66d. We also investigate an effect of the stellar rotational signal on the derivation of the planetary parameters, in particular the eccentricity of the innermost planet. Using photometry we determine the stellar rotational period to be close to 68d and we also detect this signal in the residuals of a three-planet fit to the RV data and the spectral activity indicators. From our stability analysis we derive a lower limit on the inclination of the system with the assumption of coplanar orbits which is i_min_=0.9deg. From the absence of a transit event with TESS, we derive an upper limit of the inclination of i_max_=87.43deg. YZ Ceti is a prime example of a system where strong aliasing hindered the determination of the orbital periods of exoplanets. Additionally, stellar activity influences the derivation of planetary parameters and modeling them correctly is important for the reliable estimation of the orbital parameters in this specific compact system. Stability considerations then allow additional constraints to be placed on the planetary parameters.
25482. YZ Ceti radial velocity curve
ID:
ivo://CDS.VizieR/J/A+A/605/L11
Title:
YZ Ceti radial velocity curve
Short Name:
J/A+A/605/L11
Date:
21 Oct 2021
Publisher:
CDS
Description:
Exoplanet surveys have shown that systems with multiple low-mass planets on compact orbits are common. Except for a few cases, however, the masses of these planets are generally unknown. At the very end of the main sequence, host stars have the lowest mass and hence offer the largest reflect motion for a given planet. In this context, we monitored the low-mass (0.13M_{sun}_) M dwarf YZ Cet (GJ 54.1, HIP 5643) intensively and obtained radial velocities and stellar-activity indicators derived from spectroscopy and photometry, respectively. We find strong evidence that it is orbited by at least three planets in compact orbits (Porb=1.97, 3.06, 4.66 days), with the inner two near a 2:3 mean-motion resonance. The minimum masses are comparable to the mass of Earth (Msini=0.75+/-0.13, 0.98+/-0.14, and 1.14+/-0.17M_{earth}_), and they are also the lowest masses measured by radial velocity so far. We note the possibility for a fourth planet with an even lower mass of Msini=0.472+/-0.096 Mearth at Porb=1.04-days. An n-body dynamical model is used to place further constraints on the system parameters. At 3.6 parsecs, YZ Cet is the nearest multi-planet system detected to date.
25483. z<0.06 active black hole galaxies from SDSS-DR8
ID:
ivo://CDS.VizieR/J/ApJ/775/116
Title:
z<0.06 active black hole galaxies from SDSS-DR8
Short Name:
J/ApJ/775/116
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a sample of 151 dwarf galaxies (10^8.5^<~M_*_<~10^9.5^M_{sun}_) that exhibit optical spectroscopic signatures of accreting massive black holes (BHs), increasing the number of known active galaxies in this stellar-mass range by more than an order of magnitude. Utilizing data from the Sloan Digital Sky Survey Data Release 8 and stellar masses from the NASA-Sloan Atlas, we have systematically searched for active BHs in ~25000 emission-line galaxies with stellar masses comparable to the Magellanic Clouds and redshifts z<0.055. Using the narrow-line [OIII]/H{beta} versus [NII]/H{alpha} diagnostic diagram, we find photoionization signatures of BH accretion in 136 galaxies, a small fraction of which also exhibit broad H{alpha} emission. For these broad-line active galactic nucleus (AGN) candidates, we estimate BH masses using standard virial techniques and find a range of 10^5^<~M_BH_<~10^6^M_{sun}_ and a median of M_BH_~2x10^5^M_{sun}_. We also detect broad H{alpha} in 15 galaxies that have narrow-line ratios consistent with star-forming galaxies. Follow-up observations are required to determine if these are true type 1 AGN or if the broad H{alpha} is from stellar processes. The median absolute magnitude of the host galaxies in our active sample is M_g_=-18.1mag, which is ~1-2mag fainter than previous samples of AGN hosts with low-mass BHs. This work constrains the smallest galaxies that can form a massive BH, with implications for BH feedback in low-mass galaxies and the origin of the first supermassive BH seeds.
25484. z>~5 AGN in Chandra Deep Field-South
ID:
ivo://CDS.VizieR/J/MNRAS/448/3167
Title:
z>~5 AGN in Chandra Deep Field-South
Short Name:
J/MNRAS/448/3167
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate early black hole (BH) growth through the methodical search for z>~5 active galactic nuclei (AGN) in the Chandra} Deep Field South. We base our search on the Chandra 4-Ms data with flux limits of 9.1x10^-18^erg/s/cm2 (soft, 0.5-2keV) and 5.5x10^-17^erg/s/cm2 (hard, 2-8keV). At z~5, this corresponds to luminosities as low as ~10^42^erg/s/cm2 (~10^43^erg/s) in the soft (hard) band and should allow us to detect Compton-thin AGN with M_BH_>10^7^M_{sun}_ and Eddington ratios >0.1. Our field (0.03deg^2^) contains over 600 z~5 Lyman Break Galaxies. Based on lower redshift relations, we would expect ~20 of them to host AGN. After combining the Chandra data with Great Observatories Origins Deep Survey (GOODS)/Advanced Camera for Surveys (ACS), CANDELS/Wide Field Camera 3 and Spitzer/Infrared Array Camera data, the sample consists of 58 high-redshift candidates. We run a photometric redshift code, stack the GOODS/ACS data, apply colour criteria and the Lyman Break Technique and use the X-ray Hardness Ratio. We combine our tests and using additional data find that all sources are most likely at low redshift. We also find five X-ray sources without a counterpart in the optical or infrared which might be spurious detections. We conclude that our field does not contain any convincing z>~5 AGN. Explanations for this result include a low BH occupation fraction, a low AGN fraction, short, super-Eddington growth modes, BH growth through BH-BH mergers or in optically faint galaxies. By searching for z>~5 AGN, we are setting the foundation for constraining early BH growth and seed formation scenarios.
25485. Z And UBV photometry and equivalent widths
ID:
ivo://CDS.VizieR/J/ApJ/636/1002
Title:
Z And UBV photometry and equivalent widths
Short Name:
J/ApJ/636/1002
Date:
21 Oct 2021
Publisher:
CDS
Description:
We describe observational evidence for a new kind of interacting binary star outburst that involves both an accretion instability and an increase in thermonuclear shell burning on the surface of an accreting white dwarf. We refer to this new type of eruption as a combination nova. In late 2000, the prototypical symbiotic star Z Andromedae brightened by roughly 2mag in the optical. We observed the outburst in the radio with the VLA and MERLIN, in the optical both photometrically and spectroscopically, in the far-ultraviolet with FUSE, and in the X-rays with both Chandra and XMM-Newton.
25486. z=4.5 and z=5.7 LAEs properties with Spitzer
ID:
ivo://CDS.VizieR/J/ApJ/813/78
Title:
z=4.5 and z=5.7 LAEs properties with Spitzer
Short Name:
J/ApJ/813/78
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results from a stellar population modeling analysis of a sample of 162 z=4.5 and 14 z=5.7 Ly{alpha} emitting galaxies (LAEs) in the Bootes field, using deep Spitzer/IRAC data at 3.6 and 4.5 {mu}m from the Spitzer Ly{alpha} Survey, along with Hubble Space Telescope NICMOS and WFC3 imaging at 1.1 and 1.6 {mu}m for a subset of the LAEs. This represents one of the largest samples of high-redshift LAEs imaged with Spitzer IRAC. We find that 30/162 (19%) of the z=4.5 LAEs and 9/14 (64%) of the z=5.7 LAEs are detected at >=3{sigma} in at least one IRAC band. Individual z=4.5 IRAC-detected LAEs have a large range of stellar mass, from 5x10^8^-10^11^ M_{sun}_. One-third of the IRAC-detected LAEs have older stellar population ages of 100 Myr^-1^ Gyr, while the remainder have ages <100 Myr. A stacking analysis of IRAC-undetected LAEs shows this population to be primarily low mass (8-20x10^8^ M_{sun}_) and young (64-570 Myr). We find a correlation between stellar mass and the dust-corrected ultraviolet-based star formation rate (SFR) similar to that at lower redshifts, in that higher mass galaxies exhibit higher SFRs. However, the z=4.5 LAE correlation is elevated 4-5 times in SFR compared to continuum-selected galaxies at similar redshifts. The exception is the most massive LAEs which have SFRs similar to galaxies at lower redshifts suggesting that they may represent a different population of galaxies than the traditional lower-mass LAEs, perhaps with a different mechanism promoting Ly{alpha} photon escape.
25487. z<0.06 broad-line AGN emission-line measures
ID:
ivo://CDS.VizieR/J/ApJ/813/82
Title:
z<0.06 broad-line AGN emission-line measures
Short Name:
J/ApJ/813/82
Date:
21 Oct 2021
Publisher:
CDS
Description:
Scaling relations between central black hole (BH) mass and host galaxy properties are of fundamental importance to studies of BH and galaxy evolution throughout cosmic time. Here we investigate the relationship between BH mass and host galaxy total stellar mass using a sample of 262 broad-line active galactic nuclei (AGNs) in the nearby universe (z<0.055), as well as 79 galaxies with dynamical BH masses. The vast majority of our AGN sample is constructed using Sloan Digital Sky Survey spectroscopy and searching for Seyfert-like narrow-line ratios and broad H{alpha} emission. BH masses are estimated using standard virial techniques. We also include a small number of dwarf galaxies with total stellar masses M_stellar_<~10^9.5^M_{sun}_ and a subsample of the reverberation-mapped AGNs. Total stellar masses of all 341 galaxies are calculated in the most consistent manner feasible using color-dependent mass-to-light ratios. We find a clear correlation between BH mass and total stellar mass for the AGN host galaxies, with M_BH_{propto}M_stellar_, similar to that of early-type galaxies with dynamically detected BHs. However, the relation defined by the AGNs has a normalization that is lower by more than an order of magnitude, with a BH-to-total stellar mass fraction of M_BH_/M_stellar_~0.025% across the stellar mass range 10^8^<=M_stellar_/M_{sun}_<=10^12^. This result has significant implications for studies at high redshift and cosmological simulations in which stellar bulges cannot be resolved.
25488. z'BVRi' photometry of ClG 0016+1609
ID:
ivo://CDS.VizieR/J/MNRAS/379/1546
Title:
z'BVRi' photometry of ClG 0016+1609
Short Name:
J/MNRAS/379/1546
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report a definitive confirmation of a large-scale structure around the super rich cluster CL0016+1609 at z=0.55. We made spectroscopic follow-up observations with Faint Object Camera and Spectrograph (FOCAS) on Subaru along the large filamentary structure identified in our previous photometric studies, including some subclumps already found by other authors.
25489. z<0.16 CIV absorbers from HST/COS QSOs spectra
ID:
ivo://CDS.VizieR/J/ApJ/815/91
Title:
z<0.16 CIV absorbers from HST/COS QSOs spectra
Short Name:
J/ApJ/815/91
Date:
21 Oct 2021
Publisher:
CDS
Description:
To investigate the evolution of metal-enriched gas over recent cosmic epochs as well as to characterize the diffuse, ionized, metal-enriched circumgalactic medium, we have conducted a blind survey for CIV absorption systems in 89 QSO sightlines observed with the Hubble Space Telescope Cosmic Origins Spectrograph. We have identified 42 absorbers at z<0.16, comprising the largest uniform blind sample size to date in this redshift range. Our measurements indicate an increasing CIV absorber number density per comoving path length (dN/dX=7.5+/-1.1) and modestly increasing mass density relative to the critical density of the universe ({Omega}_CIV_=10.0+/-1.5x10^-8^) from z~1.5 to the present epoch, consistent with predictions from cosmological hydrodynamical simulations. Furthermore, the data support a functional form for the column density distribution function that deviates from a single power law, also consistent with independent theoretical predictions. As the data also probe heavy element ions in addition to CIV at the same redshifts, we identify, measure, and search for correlations between column densities of these species where components appear to be aligned in velocity. Among these ion-ion correlations, we find evidence for tight correlations between CII and SiII, CII and SiIII, and CIV and SiIV, suggesting that these pairs of species arise in similar ionization conditions. However, the evidence for correlations decreases as the difference in ionization potential increases. Finally, when controlling for observational bias, we find only marginal evidence for a correlation (86.8% likelihood) between the Doppler line width b(CIV) and column density N(CIV).
25490. z~5.7 C IV absorption systems
ID:
ivo://CDS.VizieR/J/MNRAS/442/946
Title:
z~5.7 C IV absorption systems
Short Name:
J/MNRAS/442/946
Date:
21 Oct 2021
Publisher:
CDS
Description:
Metal absorption systems are products of star formation. They are believed to be associated with massive star-forming galaxies, which have significantly enriched their surroundings. To test this idea with high column density CIV absorption systems at z~5.7, we study the projected distribution of galaxies and characterize the environment of CIV systems in two independent quasar lines of sight: J103027.01+052455.0 and J113717.73+354956.9. Using wide-field photometry (~80x60h^-1^ comoving Mpc), we select bright (M_UV(1350{AA})_<~-21.0mag) Lyman break galaxies (LBGs) at z~5.7 in a redshift slice {Delta}z~0.2 and we compare their projected distribution with z~5.7 narrow-band selected Lyman alpha emitters (LAEs, {Delta}z~0.08). We find that the CIV systems are located more than 10h^-1^ projected comoving Mpc from the main concentrations of LBGs and no candidate is closer than ~5h^-1^ projected comoving Mpc. In contrast, an excess of LAEs - lower mass galaxies - is found on scales of ~10h^-1^ comoving Mpc, suggesting that LAEs are the primary candidates for the source of the CIV systems. Furthermore, the closest object to the system in the field J1030+0524 is a faint LAE at a projected distance of 212h^-1^ physical kpc. However, this work cannot rule out undiscovered lower mass galaxies as the origin of these absorption systems. We conclude that, in contrast with lower redshift examples (z<~3.5), strong CIV absorption systems at z~5.7 trace low-to-intermediate density environments dominated by low-mass galaxies. Moreover, the excess of LAEs associated with high levels of ionizing flux agrees with the idea that faint galaxies dominate the ionizing photon budget at this redshift.

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