PG 0844+349

PG 0844+349, also known as TON 951 (abbreviation of Tonantzintla 951), is a galaxy in the southern constellation Lynx, near the border of Cancer. Its redshift is 0.064000, putting the galaxy at 849 million light-years away from Earth.^[1]

PG 0844+349
PG 0844+349 and its companion galaxy captured by SDSS
Observation data (J2000 epoch)
Constellation	Lynx
Right ascension	08h 47m 42.47s
Declination	+34d 45m 04.40s
Redshift	0.064000
Heliocentric radial velocity	19,187 km/s
Distance	849 Mly (260.3 Mpc)
Apparent magnitude (V)	0.10
Apparent magnitude (B)	0.13
Surface brightness	13.5
Characteristics
Type	Sp (d), Sy1,
Notable features	Seyfert galaxy containing a quasar
Other designations
TON 951, RBS 724, PGC 24702, RX J0847.6+3445, LAMOST J084742.44+344504.4, CSO 204, 2E 2048, 1ES 0844+349, 2PBC J0848.2+3443

Observation history

PG 0844+349 was first discovered in 1957 by the Tonantzintla Observatory who was searching for blue stellar objects (mainly white dwarfs) as quasar candidates.^[2] Because quasars were not identified until 1963,^[3] the nature of this object was unknown. Studying photographic plates that were taken with the 0.7 m Schmidt telescope, it was discovered PG 0844+349 has a Seyfert 1 spectrum, classifying it as a quasar. Mexican astronomers Braulio Iriarte and Enrique Chavira subsequently listed it as the 951st object in the Tonantzintla Catalogue.^[4] The same case was applied with TON 618.

In 2009, PG 0844+349 was observed again, by the Swift observatory, and it was noted to have a weak X-ray state. Several weeks later, a follow-up observation by XMM-Newton found it showing a spectral hardening and substantial curvature. This shows that PG 0844+349 is in the phase of reflection-dominated state and its light bending scenario can be accounted for short-term ( ∼1000 s) spectral variability in its source.^[5]

Characteristics

PG 0844+349 has an active galactic nucleus. It is classified a Seyfert type 1.0 galaxy,^[6] containing two sets of emission lines superimposed onto each other. One set of lines is a low-density (electron density n_e  10³-10⁶ cm⁻³) ionized gas that has widths which corresponds to velocities of several hundred kilometers per second. The other is a set of broad lines, with widths as high as 10⁴ km s⁻¹; but the absence of broad forbidden-line emission indicates that the broad-line gas is of high density (n_e  10⁹ cm⁻³ or higher).^[7] It can be said PG 0844+349 is a narrow-line Seyfert 1 galaxy considered having all characteristics of type 1 Seyfert galaxies,^[8] but it does not have any hardness ratio variations as a single observation finds no strong correlation between the hardness ratio and the continuum luminosity.^[9]

PG 0844+349 is also a quasar but with low luminosity.^[2] The quasar host is a disturbed face-on barred spiral galaxy,^[10][11] which is found interacting with its companion galaxy, 2MASX J08474179+3444405.^[12] Both galaxies show signs of gravitational distortion, in which tidal tails and a hot blue stellar component can be seen.^[2] Through the interaction with 2MASX J08474179+3444405, this causes the activity in the central region of PG 0844+349 to awaken causing it to create more star formation with its black hole mass suppressed by its increasing starburst luminosity.^[13] This gives it its quasar appearance.

Observation

In a 2002 observation of PG 0844+349, it was found to be in a historically high state compared to the prior observation by X-rays. This shows a featureless spectrum containing a strong soft excess that is over the extrapolation of a hard power law. From the acceptable descriptions of the spectral continuum, the comptonization model is represented by its Gamma_{soft} ~ 2.75, Gamma_{hard} ~ 2.25 and a break energy of E_{break} of ~ 1.35 keV, meaning the temperature is low and have a higher optical depth than in broad-line Seyfert galaxies. Further observation shows the flux in PG 0844+349 varying achromatically on its time scale, in relatively few seconds by ~ 25%. This puts constraints on the current models of Comptonizing accretion disk coronae.^[14]

According to observation from the ASCA satellite, researchers has found PG 0844+349 has a high state with a photon index of 1.98 and an Fe Kα line with EW ~ 300 eV. Even its X-ray flux ranging in the 2-10 keV band is considered highly variable. They found that the fastest variation detected reaches up to 2 × 10⁴ s but less than 60%. Given the state of PG 0844+349, the measured excess variance fits well in comparison with the L_{2-10 keV} relation for Seyfert 1 galaxies; the flux variability in the 0.5-2.0 keV band has a slightly higher amplitude than in the 2-10 keV band. Researchers noted the optical microvariability of PG 0844+349 is driven by reprocessing of variable X-ray fluxes, provided one-half of its absorbed X-rays are reradiated in the optical-to-ultraviolet band.^[15]

Black hole

The supermassive black hole in PG 0844+349 has an estimated solar mass of 2.138×10⁷.^[16] This makes the galaxy contain one of the largest black holes, but a lower black hole mass putting it between Messier 58 and Centaurus A. Only TON 618 has a higher black hole solar mass of 4.07×10¹⁰ compared to PG 0844+349.^[17]