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Register a new userIntroducing the Search for Intermediate-mass Black-hole In Nearby Galaxy (SIBLING) Survey
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Added by
Jorge Mart\\'inez-Palomera Ph.D.
Publication date
2019
fields
Physics
and research's language is
English
Authors
Jorge Martinez-Palomera
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Intermediate mass black holes (IMBHs) have masses between the $10^2!-!10^6$ M$_odot$ and are key to our understanding of the formation of massive black holes. The known population of IMBH remains small, with a few hundred candidates and only a handful of them confirmed as bona-fide IMBHs. Until now, the most widely used selection method is based on spectral analysis. Here we present a methodology to select IMBH candidates via optical variability analysis of the nuclear region of local galaxies ($z leqslant 0.35$). Active IMBH accreting at low rates show small amplitude variability with time scales of hours, as it is seen in one of the known IMBH NGC4395. We found a sample of $sim !500$ galaxies evidencing fast and small amplitude variation in their weekly based light curves. We estimate an average occupancy fraction of 4% and a surface density of $sim !3$ deg$^{-2}$, which represent an increase by a factor of $sim!40$ compared to previous searches. A large fraction ($78%$) of the candidates are in spiral galaxies. We preliminary confirm the AGN nature of 22 sources via BPT diagrams using SDSS legacy spectra. Further confirmation of these candidates will require multiwavelength observations, especially in X-ray and radio bands.
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We report the serendipitous discovery of a bright point source flare in the Abell cluster 1795 with archival EUVE and Chandra observations. Assuming the EUVE emission is associated with the Chandra source, the X-ray 0.5-7 keV flux declined by a factor of ~2300 over a time span of 6 years, following a power-law decay with index ~2.44+-0.40. The Chandra data alone vary by a factor of ~20. The spectrum is well fit by a blackbody with a constant temperature of kT~0.09 keV (~10^6 K). The flare is spatially coincident with the nuclear region of a faint, inactive galaxy with a photometric redshift consistent at the one sigma level with the cluster (z=0.062476). We argue that these properties are indicative of a tidal disruption of a star by a black hole with log(M_BH/M_sun)~5.5+-0.5. If so, such a discovery indicates that tidal disruption flares may be used to probe black holes in the intermediate mass range, which are very difficult to study by other means.
We present the results of a recent reverberation mapping campaign for UGC 06728, a nearby low-luminosity Seyfert 1 in a late-type galaxy. Nightly monitoring in the spring of 2015 allowed us to determine an H$beta$ time delay of $tau = 1.4 pm 0.8$ days. Combined with the width of the variable H$beta$ line profile, we determine a black hole mass of $M_{rm BH} = (7.1 pm 4.0) times 10^5$ M$_{odot}$. We also constrain the bulge stellar velocity dispersion from higher-resolution long slit spectroscopy along the galaxy minor axis and find $sigma_{star} = 51.6 pm 4.9$ km s$^{-1}$. The measurements presented here are in good agreement with both the $R_{rm BLR} - L$ relationship and the $M_{rm BH}-sigma_{star}$ relationship for AGNs. Combined with a previously published spin measurement, our mass determination for UGC 06728 makes it the lowest-mass black hole that has been fully characterized, and thus an important object to help anchor the low-mass end of black hole evolutionary models.
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