The search for active black holes in nearby low-mass galaxies using optical and mid-IR data

Sartori, Lia F.; Schawinski, Kevin; Treister, Ezequiel; Trakhtenbrot, Benny; Koss, Michael; Shirazi, Maryam; Oh, Kyuseok

doi:10.1093/mnras/stv2238

Cited by 110 publications

(136 citation statements)

References 79 publications

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“…With the limited sample size, it is not clear whether the red WISE color at longer wavelengths is a common feature of hard X-ray-selected low-mass AGNs. However, we note that low-mass AGNs selected using other methods, such as the BPT diagram or the presence of the He II λ4686 emission line, do not show as high a fraction of red -W W 2 3 colors (e.g., Figures 3 and 4 of Sartori et al 2015; Figure 1 of Hainline et al 2016) as our sample does, which might simply be due to the higher redshift and luminosities of our sample.…”

Section: Mid-ir Colorscontrasting

confidence: 59%

“…However, AGN identification methods based on red mid-IR colors become more ambiguous for low-luminosity AGNs (e.g., Hainline et al 2016). In particular, recent studies have found that the vast majority of low-mass galaxies with red mid-IR color do not show any sign of optical emission lines powered by AGNs (Satyapal et al 2014(Satyapal et al , 2016Sartori et al 2015;Secrest et al 2015). Several studies have also demonstrated that young, compact starbursts in dwarf galaxies can have mid-IR colors mimicking those of luminous AGNs (e.g., Griffith et al 2011;Izotov et al 2014;Hainline et al 2016).…”

Section: Mid-ir Colorsmentioning

confidence: 99%

“…For AGNs selected from low-mass galaxies based on the presence of AGN-powered optical emission lines, there have been a number of studies focusing on objects selected from the SDSS (e.g., Greene & Ho 2007b;Barth et al 2008;Dong et al 2012b;Reines et al 2013;Moran et al 2014;Sartori et al 2015), but only a fraction of these optical AGNs have soft X-ray follow-up observations. We focus on the two largest optical low-mass AGN samples with X-ray follow-up observations: the 50 AGNs with Chandra 2 ks snapshot observations discussed in Dong et al (2012a) and the 14 AGNs with deeper XMM-Newton observations (>10 ks) from Ludlam et al (2015).…”

Section: X-ray Propertiesmentioning

confidence: 99%

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Hard X-Ray-selected AGNs in Low-mass Galaxies from the NuSTAR Serendipitous Survey

Chen

Brandt

Reines

et al. 2017

ApJ

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We present a sample of 10 low-mass active galactic nuclei (AGNs) selected from the 40-month Nuclear Spectroscopic Telescope Array (NuSTAR) serendipitous survey. The sample is selected to have robust NuSTAR detections at -3 24 keV, to be at < z 0.3, and to have optical r-band magnitudes at least 0.5mag fainter than an  L galaxy at its redshift. The median values of absolute magnitude, stellar mass, and 2-10 X-ray luminosity of our sample are á ñ = -M 20.03, and á ñ =-L 3.1 10 2 10 keV 42 erg s −1 , respectively. Five objects have detectable broad Hα emission in their optical spectra, indicating black hole masses of ( -) ☉ M 1.1 10.4 10 6 . We find that -+ 30 % 10 17 of the galaxies in our sample do not show AGN-like optical narrow emission lines, and one of the 10 galaxies in our sample, J115851+4243.2, shows evidence for heavy X-ray absorption. This result implies that a non-negligible fraction of low-mass galaxies might harbor accreting massive black holes that are missed by optical spectroscopic surveys and <10 keV X-ray surveys. The mid-IR colors of our sample also indicate that these optically normal low-mass AGNs cannot be efficiently identified with typical AGN selection criteria based on Wide Field Infrared Survey Explorer colors. While the hard (>10 keV) X-rayselected low-mass AGN sample size is still limited, our results show that sensitive NuSTAR observations are capable of probing faint hard X-ray emission originating from the nuclei of low-mass galaxies out to moderate redshift ( < z 0.3), thus providing a critical step in understanding AGN demographics in low-mass galaxies.

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Section: Mid-ir Colorscontrasting

confidence: 59%

Section: Mid-ir Colorsmentioning

confidence: 99%

Section: X-ray Propertiesmentioning

confidence: 99%

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Hard X-Ray-selected AGNs in Low-mass Galaxies from the NuSTAR Serendipitous Survey

Chen

Brandt

Reines

et al. 2017

ApJ

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“…At high redshift the occupation fraction might however be lower than 100% (Treister et al 2013;Weigel et al 2015;Trakhtenbrot et al 2016). Furthermore, depending on the black hole seed formation mechanism, the black hole occupation fraction in dwarf galaxies might be lower than in more massive galaxies (Volonteri et al 2008;Natarajan 2011;Greene 2012;Reines et al 2013;Moran et al 2014;Sartori et al 2015). If this possible mass dependence is not taken into account, the black hole occupation fraction can be defined in the following way using the stellar mass and black hole mass function:…”

Section: Mcmcmentioning

confidence: 99%

AGNs and Their Host Galaxies in the Local Universe: Two Mass-independent Eddington Ratio Distribution Functions Characterize Black Hole Growth

Weigel

Schawinski

Čaplar

et al. 2017

ApJ

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We use a phenomenological model to show that black hole growth in the local Universe (z 0.1) can be described by two separate, mass independent Eddington ratio distribution functions (ERDFs). We assume that black holes can be divided into two independent groups: those with radiatively efficient accretion, primarily hosted by optically blue and green galaxies, and those with radiatively inefficient accretion, which are mainly found in red galaxies. With observed galaxy stellar mass functions as input, we show that the observed AGN luminosity functions can be reproduced by using mass independent, broken power law shaped ERDFs. We use the observed hard X-ray and 1.4 GHz radio luminosity functions to constrain the ERDF for radiatively efficient and inefficient AGN, respectively. We also test alternative ERDF shapes and mass dependent models. Our results are consistent with a mass independent AGN fraction and AGN hosts being randomly drawn from the galaxy population. We argue that the ERDF is not shaped by galaxy-scale effects, but by how efficiently material can be transported from the inner few parsecs to the accretion disc. Our results are incompatible with the simplest form of mass quenching where massive galaxies host higher accretion rate AGN. Furthermore, if reaching a certain Eddington ratio is a sufficient condition for maintenance mode, it can occur in all red galaxies, not just the most massive ones.

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“…In recent years, there have been a number of discoveries of AGNs in low mass galaxies or galaxies that lack classical bulges, suggesting that black holes do exist in the low bulge mass regime and are more common than previously thought (e.g., Filippenko & Ho 2003;Barth et al 2004;Satyapal et al 2007;Satyapal et al 2008;Satyapal et al 2009;Dewangan et al 2008;Shields et al 2008;Ghosh et al 2008;Izotov & Thuan 2008;Desroches & Ho 2009;Gliozzi et al 2009;McAlpine et al 2011;Jiang et al 2011;Reines et al 2011;Reines & Deller 2012;Secrest et al 2012;Ho et al 2012;Secrest et al 2013;Simmons et al 2013;Dong et al 2012;Araya Salvo et al 2012;Reines et al 2013;Coelho et al 2013;Schramm et al 2013;Bizzocchi et al 2014;Satyapal et al 2014;Reines et al 2014;Maksym et al 2014;Moran et al 2014;Yuan et al 2014;Secrest et al 2015a;Miller et al 2015;Sartori et al 2015;Mezcua et al 2016;Lemons et al 2015).…”

Section: Introductionmentioning

confidence: 99%

OBSCURED AGNs IN BULGELESS HOSTS DISCOVERED BY WISE: THE CASE STUDY OF SDSS J1224+5555

Satyapal¹,

Secrest²,

Rothberg³

et al. 2016

ApJ

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There is mounting evidence that supermassive black holes form and grow in bulgeless galaxies. However, a robust determination of the fraction of AGNs in bulgeless galaxies, an important constraint to models of supermassive black hole seed formation and merger-free models of AGN fueling, is unknown, since optical studies have been shown to be incomplete for low mass AGNs. In a recent study using the Wide-field Infrared Survey Explorer, we discovered hundreds of bulgeless galaxies that display mid-infrared signatures of extremely hot dust suggestive of powerful accreting massive black holes, despite having no signatures of black hole activity at optical wavelengths. Here we report X-ray follow-up observations of J122434.66+555522.3, a nearby (z = 0.052) isolated bulgeless galaxy that contains an unresolved X-ray source detected at the 3σ level by XMM-Newton with an observed luminosity uncorrected for intrinsic absorption of L 2−10 keV = (1.1 ± 0.4) × 10 40 erg s −1 . Groundbased near-infrared spectroscopy with the Large Binocular Telescope together with multiwavelength observations from ultraviolet to millimeter wavelengths together suggest that J1224+5555 harbors a highly absorbed AGN with an intrinsic absorption of N H > 10 24 cm −2 . The hard X-ray luminosity of the putative AGN corrected for absorption is L 2−10 keV ∼ 3 × 10 42 erg s −1 , which, depending on the bolometric correction factor, corresponds to a bolometric luminosity of the AGN of 6 × 10 43 erg s3 × 10 44 erg s −1 , and a lower mass limit for the black hole of M BH ≃ 2 × 10 6 M ⊙ , based on the Eddington limit. While enhanced X-ray emission and hot dust can be produced by star formation in extremely low metallicity environments typical in dwarf galaxies, J1224+5555 has a stellar mass of ∼ 2.0 × 10 10 M ⊙ , and an above solar metallicity (12+log O/H=9.11), typical of our WISE-selected bulgeless galaxies sample. While collectively, these observations suggest the presence of an AGN, we caution that identifying obscured AGNs in the low luminosity regime is challenging, and often requires multi wavelength observations.These observations suggest that low luminosity AGNs can be heavily obscured and reside in optically quiescent galaxies, adding to the growing body of evidence that the fraction of bulgeless galaxies with accreting black holes may be significantly underestimated based on optical studies.

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The search for active black holes in nearby low-mass galaxies using optical and mid-IR data

Cited by 110 publications

References 79 publications

Hard X-Ray-selected AGNs in Low-mass Galaxies from the NuSTAR Serendipitous Survey

Hard X-Ray-selected AGNs in Low-mass Galaxies from the NuSTAR Serendipitous Survey

AGNs and Their Host Galaxies in the Local Universe: Two Mass-independent Eddington Ratio Distribution Functions Characterize Black Hole Growth

OBSCURED AGNs IN BULGELESS HOSTS DISCOVERED BY WISE: THE CASE STUDY OF SDSS J1224+5555

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