2025ApJS..281...60L

Query : 2025ApJS..281...60L

2025ApJS..281...60L - Astrophys. J., Suppl. Ser., 281, 60 (2025/December-0)

Optimizing Long-term Variability of Active Galactic Nucleus Light Curves. I. A Case Study with ZTF Observations in the EGS Field.

LIN J., ZHENG Z.-Y., MA B., LONG L., XIE Y., LIN P., LIN R. and JI X.

Abstract (from CDS):

Optical variability is a key observational probe for studying the accretion dynamics and central engine physics of active galactic nuclei (AGNs). The quality and completeness of light curves have a direct impact on variability studies, particularly for faint AGNs and high-redshift AGNs. To improve the quality of long-term light curves for AGNs, we bin and stack multiepoch images balancing the image depths and temporal resolution. As a case study, we apply this method to Zwicky Transient Facility (ZTF) observations in the Extended Groth Strip (EGS) field, where the overlapping region covers an area of about 370 arcmin2 and includes g-band and r-band data taken from 2018 March to 2024 December. The coadded images are approximately 2.0-2.5 mag deeper than the ZTF single-epoch images. With coadded images, we construct light curves for 73 AGNs in the EGS field. Compared to the traditional ZTF light curves, our light curves maintain consistent long-term variability trends but with higher photometric precision. Furthermore, this method can help detect AGNs with weak variability, which are missed from the traditional ZTF data due to the noisy light curves or being below the detection limit in ZTF's single-epoch exposure. Among the 73 AGNs, the majority exhibit a bluer-when-brighter trend on long-term timescales, which is consistent with previous studies. This work offers insights for optimizing AGN light curves in both current and upcoming all-sky time-domain surveys.

Abstract Copyright: © 2025. The Author(s). Published by the American Astronomical Society.

Journal keyword(s): Light curves - Active galactic nuclei - Time domain astronomy

Simbad objects: 74

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Number of rows : 74
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 DEEP2-GRS 12004836 AGN 14 16 45.17211 +52 26 00.4699   21.667   20.563 20.177 ~ 4 0
2 SDSS J141645.39+522905.9 QSO 14 16 45.398 +52 29 05.99   22.286 21.766 21.21 20.860 ~ 22 0
3 SDSS J141649.44+522530.9 QSO 14 16 49.4397635832 +52 25 30.883974132   21.996 20.950 20.00 20.578 ~ 31 0
4 DEEP2-GRS 12004778 AGN 14 16 50.47109 +52 25 56.2121   21.797   20.490 20.000 ~ 3 0
5 CXOEGS J141654.3+522440 AGN 14 16 54.27127 +52 24 39.9264   20.475   19.247 18.791 ~ 11 0
6 DEEP2-GRS 12004503 AGN 14 16 59.85546 +52 25 10.6638   22.89   21.52 21.04 ~ 3 0
7 2MASS J14170417+5224533 AGN 14 17 04.171 +52 24 53.32   21.430 20.991 19.421 18.742 ~ 16 0
8 SDSS J141705.72+523230.5 AGN 14 17 05.734 +52 32 30.85   21.41   21.21 20.93 ~ 9 0
9 SDSS J141710.57+522829.1 QSO 14 17 10.558 +52 28 28.94   23.289 22.640 22.03 21.827 ~ 21 0
10 DEEP2-GRS 12008528 AGN 14 17 14.9467 +52 29 12.200   22.142   21.106 20.690 ~ 5 0
11 SDSS J141715.03+522312.7 QSO 14 17 15.0397138056 +52 23 12.720211044   22.173 21.894 21.33 21.471 ~ 32 0
12 DEEP2-GRS 11051192 AGN 14 17 16.79233 +52 24 06.9575   20.605   19.284 18.771 ~ 4 0
13 CXO J141722.9+523143 AGN 14 17 22.9434 +52 31 43.656   22.78   21.302 20.666 ~ 15 0
14 3XMM J141723.4+523153 Sy1 14 17 23.385 +52 31 53.89   21.909 21.894 21.262 20.846 ~ 39 0
15 DEEP2-GRS 11051225 AGN 14 17 23.52 +52 23 52.4   21.61   20.439 20.082 ~ 3 0
16 DEEP2-GRS 12008271 AGN 14 17 23.5514 +52 27 57.273   22.11   20.299 19.644 ~ 4 0
17 3XMM J141724.5+523025 Sy1 14 17 24.5951767656 +52 30 24.769792728   20.226 20.382 19.992 19.664 ~ 69 0
18 DEEP2-GRS 12012578 AGN 14 17 25.2356 +52 31 37.803   21.132   20.852 20.575 ~ 5 0
19 DEEP2-GRS 12016754 AGN 14 17 28.66 +52 36 51.5   21.167   19.733 19.259 ~ 2 0
20 CFRS 14.1446 AGN 14 17 29.59 +52 27 59.5   21.234   20.233 19.910 ~ 15 0
21 CFRS 14.1432 AGN 14 17 30.15 +52 30 33.3   21.417   20.655 20.273 ~ 9 0
22 DEEP2-GRS 12016803 AGN 14 17 31.13 +52 34 10.4   21.396   19.864 19.352 ~ 3 0
23 CFRS 14.1399 AGN 14 17 31.38 +52 31 07.3   23.00   22.09 21.88 ~ 7 0
24 CFRS 14.1351 AGN 14 17 33.59 +52 31 26.6   22.72   21.112 20.560 ~ 9 0
25 ACS-GC 12012543 AGN 14 17 33.812 +52 33 49.56   22.39 22.230 21.189 20.610 ~ 20 0
26 [VV2006] J141734.8+522809 QSO 14 17 34.8501450528 +52 28 10.633687536   20.980 20.684 20.82 20.292 ~ 31 0
27 QSO B1415+5244 QSO 14 17 35.9488358832 +52 30 29.776951944   20.977 20.250 19.87 19.837 ~ 60 0
28 DEEP2-GRS 12016732 AGN 14 17 36.97486 +52 35 42.7626   21.560   20.893 20.592 ~ 3 0
29 DEEP2-GRS 12020784 AGN 14 17 42.89147 +52 38 11.8724   22.39   21.58 20.96 ~ 3 0
30 CFRS 14.1082 AGN 14 17 43.89 +52 32 32.1   22.44   20.750 20.178 ~ 6 0
31 SDSS J141801.94+523514.9 QSO 14 18 01.9477400448 +52 35 14.885674620   20.643 20.327 19.93 19.525 ~ 26 0
32 SDSS J141803.36+524127.7 QSO 14 18 03.3669952512 +52 41 27.858559164   19.87   20.32 19.66 ~ 20 0
33 SDSS J141804.59+523745.0 QSO 14 18 04.595 +52 37 45.04   21.30   21.16 21.15 ~ 21 0
34 CFRS 14.0393 rG 14 18 09.22 +52 30 13.4   21.555 21.47 20.571 20.151 ~ 16 0
35 SDSS J141809.71+524300.1 QSO 14 18 09.7090331928 +52 43 00.215939208   22.52   21.25 21.05 ~ 18 0
36 SDSS J141818.45+524356.0 QSO 14 18 18.4706486352 +52 43 56.083221120   21.86   22.10 21.60 ~ 22 0
37 DEEP2-GRS 12020377 AGN 14 18 22.89442 +52 39 29.1983   21.91   20.589 20.062 ~ 4 0
38 SDSS J141823.07+524118.9 QSO 14 18 23.076 +52 41 18.82   22.28   22.48 21.94 ~ 11 0
39 SDSS J141823.29+524004.3 AGN 14 18 23.291 +52 40 04.56   22.14   22.59 22.11 ~ 5 0
40 ACS-GC 12024309 AGN 14 18 29.87486 +52 42 15.1399   22.24   20.996 20.240 ~ 10 0
41 DEEP2-GRS 12024424 AGN 14 18 30.33961 +52 42 20.7842   20.959   19.639 19.136 ~ 7 0
42 DEEP2-GRS 13005158 AGN 14 18 34.47516 +52 47 59.2258   22.93   21.90 21.45 ~ 4 0
43 DEEP2-GRS 12015618 AGN 14 18 38.77288 +52 36 14.5495   22.08   20.892 20.450 ~ 3 0
44 SDSS J141842.27+523643.9 QSO 14 18 42.274 +52 36 43.97   21.32   21.07 20.87 ~ 16 0
45 CANDELS EGS F160W J141844.3+524743.2 AGN 14 18 44.29956 +52 47 43.2995   22.41   20.533 19.652 ~ 8 0
46 CANDELS EGS F160W J141845.5+524333.1 AGN 14 18 45.52191 +52 43 32.8886   20.719   19.908 19.621 ~ 7 0
47 DEEP2-GRS 13012392 AGN 14 18 47.57899 +52 51 24.7352   22.48   21.418 21.040 ~ 3 0
48 DEEP2-GRS 12020053 AGN 14 18 47.72212 +52 38 38.6112   22.253   21.453 21.145 ~ 3 0
49 AEGIS20 J141853.18+524410.7 rG 14 18 53.17 +52 44 10.7   20.484   19.248 18.745 ~ 10 0
50 CANDELS EGS F160W J141854.8+524307.3 AGN 14 18 54.83812 +52 43 07.2655   21.942   21.25 21.06 ~ 7 0
51 DEEP2-GRS 12019605 AGN 14 18 55.66 +52 39 48.8   22.46   21.170 20.750 ~ 2 0
52 CANDELS EGS F160W J141856.4+524354.3 AGN 14 18 56.39533 +52 43 54.3572   20.525   19.850 19.533 ~ 7 0
53 CANDELS EGS F160W J141857.0+524419.0 AGN 14 18 57.02566 +52 44 19.3578   22.003   20.606 20.246 ~ 7 0
54 SDSS J141857.28+524414.1 rG 14 18 57.27815 +52 44 14.1378   20.366   19.329 18.820 ~ 13 0
55 DEEP2-GRS 12019632 AGN 14 18 58.21015 +52 40 53.6199   22.38   21.411 21.23 ~ 4 0
56 DEEP2-GRS 13012101 AGN 14 18 59.56286 +52 52 54.2618   21.285   20.072 19.613 ~ 3 0
57 NAME Extended Groth Strip reg 14 19 +52.8           ~ 1023 0
58 CANDELS EGS F160W J141901.3+525012.5 AGN 14 19 01.25599 +52 50 12.6215   23.39   22.392 22.52 ~ 11 0
59 SDSS J141901.47+524509.5 QSO 14 19 01.47744 +52 45 09.4097   23.49   21.93 21.056 ~ 14 0
60 CANDELS EGS F160W J141906.5+524312.8 AGN 14 19 06.54734 +52 43 12.6449   22.85   21.034 20.575 ~ 6 0
61 AEGIS20 J141906.79+524013.9 rG 14 19 06.79155 +52 40 13.4994   19.437   18.848 18.556 ~ 5 0
62 AEGIS20 J141908.83+524400.7 rG 14 19 08.83 +52 44 00.6   21.397   20.104 19.409 ~ 5 0
63 CANDELS EGS F160W J141910.1+524912.1 AGN 14 19 10.08730 +52 49 12.0148   21.86   20.716 20.393 ~ 7 0
64 CANDELS EGS F160W J141915.2+524823.1 AGN 14 19 15.17196 +52 48 22.9252   21.929   21.150 20.931 ~ 7 0
65 SDSS J141918.07+524158.4 QSO 14 19 18.0769473504 +52 41 58.401762756   20.763   21.090 20.608 ~ 21 0
66 DEEP2-GRS 12023668 AGN 14 19 18.85262 +52 43 37.7357   22.33   21.52 21.35 ~ 4 0
67 CANDELS EGS F160W J141929.8+525206.4 AGN 14 19 29.80863 +52 52 06.3650   22.16   20.139 19.580 ~ 54 0
68 SDSS J141930.11+525159.3 rG 14 19 30.109 +52 51 59.31       19.55   ~ 7 0
69 CANDELS EGS F160W J141931.7+525155.9 AGN 14 19 31.70890 +52 51 55.8716   21.683   20.823 20.562 ~ 8 0
70 CANDELS EGS F160W J141932.1+525327.4 AGN 14 19 32.12441 +52 53 27.3114   22.39   21.561 21.35 ~ 6 0
71 CANDELS EGS F160W J141932.3+525436.8 AGN 14 19 32.28 +52 54 36.8   21.62   20.183 19.736 ~ 6 0
72 CANDELS EGS F160W J141935.3+525249.8 AGN 14 19 35.29270 +52 52 49.7073   22.48   21.043 20.506 ~ 9 0
73 CANDELS EGS F160W J141937.3+524757.6 AGN 14 19 37.25023 +52 47 57.3231   20.869   19.856 19.281 ~ 7 0
74 SDSS J141943.58+525431.3 QSO 14 19 43.586 +52 54 31.37   22.02   21.18 21.25 ~ 19 0

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