skip to main content


Title: Reverberation Mapping of IC 4329A
Abstract

We present the results of a new reverberation mapping campaign for the broad-line active galactic nucleus (AGN) in the edge-on spiral IC 4329A. Monitoring of the optical continuum withV-band photometry and broad emission-line flux variability with moderate-resolution spectroscopy allowed emission-line light curves to be measured for Hβ, Hγ, and Heiiλ4686. We find a time delay of16.32.3+2.6days for Hβ, a similar time delay of16.02.6+4.8days for Hγ, and an unresolved time delay of0.63.9+3.9days for Heii. The time delay for Hβis consistent with the predicted value from the relationship between AGN luminosity and broad-line region radius, after correction for the ∼2.4 mag of intrinsic extinction at 5100 Å. Combining the measured time delay for Hβwith the broad emission-line width and an adopted value of 〈f〉 = 4.8, we find a central supermassive black hole mass ofMBH=6.81.1+1.2×107M. Velocity-resolved time delays were measured across the broad Hβemission-line profile and may be consistent with an “M”-like shape. Modeling of the full reverberation response of Hβwas able to provide only modest constraints on some parameters, but does exhibit agreement with the black hole mass and average time delay. The models also suggest that the AGN structure is misaligned by a large amount from the edge-on galaxy disk. This is consistent with expectations from the unified model of AGNs, in which broad emission lines are expected to be visible only for AGNs that are viewed at relatively face-on inclinations.

 
more » « less
Award ID(s):
2009230 2009122
NSF-PAR ID:
10396282
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
DOI PREFIX: 10.3847
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
944
Issue:
1
ISSN:
0004-637X
Format(s):
Medium: X Size: Article No. 29
Size(s):
Article No. 29
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    We describe the results of a new reverberation mapping program focused on the nearby Seyfert galaxy NGC 3227. Photometric and spectroscopic monitoring was carried out from 2022 December to 2023 June with the Las Cumbres Observatory network of telescopes. We detected time delays in several optical broad emission lines, with Hβhaving the longest delay atτcent=4.00.9+0.9days and Heiihaving the shortest delay withτcent=0.90.8+1.1days. We also detect velocity-resolved behavior of the Hβemission line, with different line-of-sight velocities corresponding to different observed time delays. Combining the integrated Hβtime delay with the width of the variable component of the emission line and a standard scale factor suggests a black hole mass ofMBH=1.10.3+0.2×107M. Modeling of the full velocity-resolved response of the Hβemission line with the phenomenological codeCARAMELfinds a similar mass ofMBH=1.20.7+1.5×107Mand suggests that the Hβ-emitting broad-line region (BLR) may be represented by a biconical or flared disk structure that we are viewing at an inclination angle ofθi≈ 33° and with gas motions that are dominated by rotation. The new photoionization-based BLR modeling toolBELMACfinds general agreement with the observations when assuming the best-fitCARAMELresults; however,BELMACprefers a thick-disk geometry and kinematics that are equally composed of rotation and inflow. Both codes infer a radially extended and flattened BLR that is not outflowing.

     
    more » « less
  2. Abstract

    We combine our dynamical modeling black-hole mass measurements from the Lick AGN Monitoring Project 2016 sample with measured cross-correlation time lags and line widths to recover individual scale factors,f, used in traditional reverberation-mapping analyses. We extend our sample by including prior results from Code for AGN Reverberation and Modeling of Emission Lines (caramel) studies that have utilized our methods. Aiming to improve the precision of black-hole mass estimates, as well as uncover any regularities in the behavior of the broad-line region (BLR), we search for correlations betweenfand other AGN/BLR parameters. We find (i) evidence for a correlation between the virial coefficientlog10(fmean,σ)and black-hole mass, (ii) marginal evidence for a similar correlation betweenlog10(frms,σ)and black-hole mass, (iii) marginal evidence for an anticorrelation of BLR disk thickness withlog10(fmean,FWHM)andlog10(frms,FWHM), and (iv) marginal evidence for an anticorrelation of inclination angle withlog10(fmean,FWHM),log10(frms,σ), andlog10(fmean,σ). Last, we find marginal evidence for a correlation between line-profile shape, when using the root-mean-square spectrum,log10(FWHM/σ)rms, and the virial coefficient,log10(frms,σ), and investigate how BLR properties might be related to line-profile shape usingcaramelmodels.

     
    more » « less
  3. Abstract

    We present measurements of the rest-frame UV spectral slope,β, for a sample of 36 faint star-forming galaxies atz∼ 9–16 discovered in one of the deepest JWST NIRCam surveys to date, the Next Generation Deep Extragalactic Exploratory Public Survey. We use robust photometric measurements for UV-faint galaxies (down toMUV∼ −16), originally published in Leung et al., and measure values of the UV spectral slope via photometric power-law fitting to both the observed photometry and stellar population models obtained through spectral energy distribution (SED) fitting withBagpipes. We obtain a median and 68% confidence interval forβfrom photometric power-law fitting ofβPL=2.70.5+0.5and from SED fitting,βSED=2.30.1+0.2for the full sample. We show that when only two to three photometric detections are available, SED fitting has a lower scatter and reduced biases than photometric power-law fitting. We quantify this bias and find that after correction the medianβSED,corr=2.50.2+0.2. We measure physical properties for our galaxies withBagpipesand find that our faint (MUV=18.10.9+0.7) sample is low in mass (log[M*/M]=7.70.5+0.5), fairly dust-poor (Av=0.10.1+0.2mag), and modestly young (log[age]=7.80.8+0.2yr) with a median star formation rate oflog(SFR)=0.30.4+0.4Myr1. We find no strong evidence for ultrablue UV spectral slopes (β∼ −3) within our sample, as would be expected for exotically metal-poor (Z/Z< 10−3) stellar populations with very high Lyman continuum escape fractions. Our observations are consistent with model predictions that galaxies of these stellar masses atz∼ 9–16 should have only modestly low metallicities (Z/Z∼ 0.1–0.2).

     
    more » « less
  4. Abstract

    We present a Keck/MOSFIRE rest-optical composite spectrum of 16 typical gravitationally lensed star-forming dwarf galaxies at 1.7 ≲z≲ 2.6 (zmean= 2.30), all chosen independent of emission-line strength. These galaxies have a median stellar mass oflog(M*/M)med=8.290.43+0.51and a median star formation rate ofSFRHαmed=2.251.26+2.15Myr1. We measure the faint electron-temperature-sensitive [Oiii]λ4363 emission line at 2.5σ(4.1σ) significance when considering a bootstrapped (statistical-only) uncertainty spectrum. This yields a direct-method oxygen abundance of12+log(O/H)direct=7.880.22+0.25(0.150.06+0.12Z). We investigate the applicability at highzof locally calibrated oxygen-based strong-line metallicity relations, finding that the local reference calibrations of Bian et al. best reproduce (≲0.12 dex) our composite metallicity at fixed strong-line ratio. At fixedM*, our composite is well represented by thez∼ 2.3 direct-method stellar mass—gas-phase metallicity relation (MZR) of Sanders et al. When comparing to predicted MZRs from the IllustrisTNG and FIRE simulations, having recalculated our stellar masses with more realistic nonparametric star formation histories(log(M*/M)med=8.920.22+0.31), we find excellent agreement with the FIRE MZR. Our composite is consistent with no metallicity evolution, at fixedM*and SFR, of the locally defined fundamental metallicity relation. We measure the doublet ratio [Oii]λ3729/[Oii]λ3726 = 1.56 ± 0.32 (1.51 ± 0.12) and a corresponding electron density ofne=10+215cm3(ne=10+74cm3) when considering the bootstrapped (statistical-only) error spectrum. This result suggests that lower-mass galaxies have lower densities than higher-mass galaxies atz∼ 2.

     
    more » « less
  5. Abstract

    We measure the metallicities of 374 red giant branch (RGB) stars in the isolated, quenched dwarf galaxy Tucana using Hubble Space Telescope narrowband (F395N) calcium H and K imaging. Our sample is a factor of ∼7 larger than what is available from previous studies. Our main findings are as follows. (i) A global metallicity distribution function (MDF) with[Fe/H]=1.550.04+0.04andσ[Fe/H]=0.540.03+0.03. (ii) A metallicity gradient of −0.54 ± 0.07 dexRe1(−2.1 ± 0.3 dex kpc−1) over the extent of our imaging (∼2.5Re), which is steeper than literature measurements. Our finding is consistent with predicted gradients from the publicly available FIRE-2 simulations, in which bursty star formation creates stellar population gradients and dark matter cores. (iii) Tucana’s bifurcated RGB has distinct metallicities: a blue RGB with[Fe/H]=1.780.06+0.06andσ[Fe/H]=0.440.06+0.07and a red RGB with[Fe/H]=1.080.07+0.07andσ[Fe/H]=0.420.06+0.06. (iv) At fixed stellar mass, Tucana is more metal-rich than Milky Way satellites by ∼0.4 dex, but its blue RGB is chemically comparable to the satellites. Tucana’s MDF appears consistent with star-forming isolated dwarfs, though MDFs of the latter are not as well populated. (v) About 2% of Tucana’s stars have [Fe/H] < −3% and 20% have [Fe/H] > −1. We provide a catalog for community spectroscopic follow-up.

     
    more » « less