The Luminous X‐Ray Source Population in M51 Observed with<i>Chandra</i>

Terashima, Yuichi; Wilson, A. S.

doi:10.1086/380505

Cited by 70 publications

(90 citation statements)

References 93 publications

(155 reference statements)

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“…This suggests that, if the nucleus of NGC 5195 is indeed currently active (as the molecular lines seem to suggest), it may be operating in the so-called radio-quiet or "high-excitation" mode characteristic of efficiently accreting massive black holes (Heckman & Best 2014), and consistent with the weak X-rays reported by Schlegel et al (2016). Alternatively, AGN signatures at optical and X-ray wavelengths previously reported by Moustakas et al (2010) and Terashima & Wilson (2004), respectively, may in fact be related to stellar processes or shocks occurring in the vicinity of the NGC 5195 nucleus (Lisenfeld & Völk 2010). If such a scenario in which the massive black hole in the center of NGC 5195 is in a quiescent state is indeed true, it is not clear what mechanism is responsible for halting AGN fueling given the abundant availability of cold gas.…”

Section: Radio-determined Star Formationsupporting

confidence: 64%

“…Although Schweizer (1977) detected ionized gas emission lines in the galaxy, Ho et al (1997) and Moustakas et al (2010) found that the ionized gas line ratios are consistent with a low ionization nuclear emission line region (Kewley et al 2006). Weak X-ray emission was found coincident with a radio source, possibly due to an active galactic nucleus (AGN), but also consistent with an ultra-luminous X-ray source origin (Terashima & Wilson 2004;Schlegel et al 2016). Sage (1990) mapped NGC 5195 in 12 CO(1-0), and observed 12 CO(2-1) and 13 CO(1-0) with the National Radio Astronomy Observatory (NRAO) 12 m single dish, showing that there was molecular gas in the galaxy.…”

Section: Introductionmentioning

confidence: 97%

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After the Interaction: An Efficiently Star-Forming Molecular Disk in NGC 5195

Alatalo

Aladro

Nyland

et al. 2016

ApJ

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We present new molecular gas maps of NGC 5195 (alternatively known as M51b) from the Combined Array for Research in Millimeter Astronomy, including 12 CO(1-0), 13 CO(1-0), CN(1 0,2 -0 0,1 ), CS(2-1), and 3 mm continuum. We also detected HCN(1-0) and HCO + (1-0) using the Onsala Space Observatory. NGC 5195 has a 12 CO/ 13 CO ratio ( 12 13 =11.4 ± 0.5) consistent with normal star-forming galaxies. The CN(1-0) intensity is higher than is seen in an average star-forming galaxy, possibly enhanced in the diffuse gas in photo-dissociation regions. Stellar template fitting of the nuclear spectrum of NGC 5195 shows two stellar populations: an 80% mass fraction of old (10 Gyr) and a 20% mass fraction of intermediate-aged (≈1 Gyr) stellar populations. This provides a constraint on the timescale over which NGC 5195 experienced enhanced star formation during its interaction with M51a. The average molecular gas depletion timescale in NGC 5195 is t á ñ dep =3.08 Gyr, a factor of »2 larger than the depletion timescales in nearby star-forming galaxies, but consistent with the depletion seen in CO-detected early-type galaxies. While radio continuum emission at centimeter and millimeter wavelengths is present in the vicinity of the nucleus of NGC 5195, we find it is most likely associated with nuclear star formation rather than radio-loud AGN activity. Thus, despite having a substantial interaction with M51a ∼1/2 Gyr ago, the molecular gas in NGC 5195 has resettled and is currently forming stars at an efficiency consistent with settled early-type galaxies.

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Section: Radio-determined Star Formationsupporting

confidence: 64%

Section: Introductionmentioning

confidence: 97%

After the Interaction: An Efficiently Star-Forming Molecular Disk in NGC 5195

Alatalo

Aladro

Nyland

et al. 2016

ApJ

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“…Terashima & Wilson (2004) studied Chandra data from 2000 and 2001 and found neither long term, nor shortterm variability in the full, soft, or hard energy bands. Since the Chandra observations from 2000 and 2001 were rejected from our sample because of the low number counts, we cannot compare our spectral fittings with theirs.…”

Section: Appendix B: Notes and Comparisons With Previous Results For mentioning

confidence: 99%

X-ray spectral variability of LINERs selected from the Palomar sample

Hernández-García

González‐Martín

Masegosa

et al. 2014

A&A

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Context. Variability is a general property of active galactic nuclei (AGN). The way in which these changes occur at X-rays is not yet clearly understood. In the particular case of low-ionization nuclear emission line region (LINER) nuclei, variations on the timescales from months to years have been found for some objects, but the main driver of these changes is still debated. Aims. The main purpose of this work is to investigate the X-ray variability in LINERs, including the main driver of these variations, and to search for possible differences between type 1 and 2 objects. Methods. We examined the 18 LINERs in the Palomar sample with data retrieved from the Chandra and/or XMM-Newton archives that correspond to observations gathered at different epochs. All the spectra for the same object were fitted simultaneously to study long-term variations. The nature of the variability patterns were studied by allowing different parameters to vary during the spectral fit. Whenever possible, short-term variations from the analysis of the light curves and long-term UV variability were studied. Results. Short-term variations are not reported in X-rays. Three LINERs are classified as non-AGN candidates in X-rays, all of them are Compton-thick candidates; none of them show variations at these frequencies, and two of them vary in the UV. Long-term X-ray variations were analyzed in 12 out of 15 AGN candidates; about half of them showed variability (7 out of the 12). At UV frequencies, most of the AGN candidates with available data are variable (five out of six). Thus, 13 AGN candidates are analyzed at UV and/or X-rays, ten of which are variable at least in one energy band. None of the three objects that do not vary in X-rays have available UV data. This means that variability on long-timescales is very common in LINERs. These X-ray variations are mainly driven by changes in the nuclear power, while changes in absorptions are found only for NGC 1052. We do not find any difference between type 1 and 2 LINERs, neither in the number of variable cases (three out of five type 1 and four out of seven type 2 LINERs), nor in the nature of the variability pattern. We find indications of an anticorrelation between the slope of the power law, Γ, and the Eddington ratio. Conclusions. LINERs are definitely variable sources irrespective of whether they are classified as optical type 1 or 2. Their BH masses, accretion rates, and variability timescales place them in the same plane as more powerful AGN at X-rays. However, our results suggest that the accretion mechanism in LINERs may be different. UV variations of some type 2 LINERs were found, this could support the hypothesis of a torus that disappears at low luminosities.

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“…Lately, observational data indicating the possible existence of IMBHs have been accruing; some of the recent analyses are due to Portegies Zwart et al (2004), Roberts et al (2004), Terashima & Wilson (2004), and Cropper et al (2004), among others. A comprehensive review of the subject of IMBHs, including similar pieces of observational evidence, is presented in Miller & Colbert (2004).…”

Section: Introductionmentioning

confidence: 99%

An Inverse Look at the Center of M15

Chakrabarty

2006

Astron J

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The observed radial and transverse velocities of individual stars in the globular cluster M15 are used as inputs to a fully nonparametric code (CHASSIS) in order to estimate the equilibrium stellar distribution function and the threedimensional mass density profile, from which are estimated the mass-to-light ratio, enclosed mass, and velocity dispersion profiles. In particular, the paper explores the possible existence of a central black hole in M15 via several runs that use the radial velocity data set, which offers kinematic measurements closer to the center of the cluster than the proper-motion data. These runs are distinguished from each other in the choice of the initial seed for the cluster characteristics; however, the profiles identified by the algorithm at the end of each run concur with each other within error bars, thus confirming the robustness of CHASSIS. The recovered density profiles are noted to exhibit unequivocal flattening interior to about 0.0525 pc. Also, the enclosed mass profile is very close to being a power-law function of radius <0.1 pc and is not horizontal. Simplistically speaking, these trends negate the possibility of the central mass being concentrated in a black hole, the lower bound on the radius of the sphere of influence of which would be k0.041 pc had it existed. However, proper analysis suggests that the mass enclosed within the inner 0.01 pc could be in the form of a black hole of mass $10 3 M under two different scenarios, which are discussed. The line-ofsight velocity dispersion is visually found to be very similar to the observed dispersion profile. The enclosed mass and velocity dispersion profiles calculated from runs done with the proper-motion data are found to be consistent with the profiles obtained with the radial velocity data.

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The Luminous X‐Ray Source Population in M51 Observed withChandra

Cited by 70 publications

References 93 publications

After the Interaction: An Efficiently Star-Forming Molecular Disk in NGC 5195

After the Interaction: An Efficiently Star-Forming Molecular Disk in NGC 5195

X-ray spectral variability of LINERs selected from the Palomar sample

An Inverse Look at the Center of M15

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