The strange case of the peculiar spiral galaxy NGC 5474

Bellazzini, M.; Annibali, F.; Tosi, M.; Mucciarelli, A.; Cignoni, M.; Beccari, G.; Nipoti, Carlo; Pascale, Raffaele

doi:10.1051/0004-6361/201937284

Cited by 10 publications

(8 citation statements)

References 43 publications

(59 reference statements)

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“…High-velocity H I gas has also been observed in the same location as the optical light (van der Hulst & Sancisi 1988; Mihos et al 2012), while intermediate-velocity H I gas has been detected between M101 and NGC 5474 (Mihos et al 2012). NGC 5474's offset bulge is usually added as further evidence of an interaction, although recent work has called that into question (Bellazzini et al 2020;Pascale et al 2021).…”

Section: Discussionmentioning

confidence: 99%

“…We also plotted several of the confirmed and candidate satellite galaxies of M101 according to Carlsten et al (2019): NGC 5474, NGC 5477, Holmberg IV, DF1, DF2, DF3, DwA, and Dw9. There is no single paper that catalogs all of the photometric properties of the M101 satellite system; quantities for each galaxy were taken from a variety of sources (de Vaucouleurs et al 1991;Taylor et al 2005;Merritt et al 2014;Bennet et al 2019;Bellazzini et al 2020). Finally, we also show the region where H II galaxies would lie, using the definition of Thuan & Martin (1981): −18.0 < M V < −13.5 and sizes less than 1 kpc, which at M101 corresponds to an angular size of 30 .…”

Section: Structural Analysismentioning

confidence: 99%

“…Pentagons denote objects whose properties were derived using SDSS data, while squares are sources with properties derived from our Burrell Schmidt imaging. Data for Local Group dwarfs are taken from McConnachie (2012) and are shown as gray circles, while known M101 satellites are shown as gray squares (de Vaucouleurs et al 1991;Taylor et al 2005;Merritt et al 2014;Bennet et al 2019;Bellazzini et al 2020). The limits for H II galaxies are shown as dashed gray lines (Thuan & Martin 1981).…”

Section: Photometric Analysismentioning

confidence: 99%

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A Deep Census of Outlying Star Formation in the M101 Group

Garner

Mihos

Harding

et al. 2021

ApJ

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We present deep, narrowband imaging of the nearby spiral galaxy M101 and its group environment to search for star-forming dwarf galaxies and outlying H II regions. Using the Burrell Schmidt telescope, we target the brightest emission lines of star-forming regions, Hα, Hβ, and [O III], to detect potential outlying star-forming regions. Our survey covers ∼6 deg 2 around M101, and we detect objects in emission down to an Hα flux level of 5.7 × 10 −17 erg s −1 cm −2 (equivalent to a limiting SFR of 1.7 × 10 −6 M yr −1 at the distance of M101). After careful removal of background contaminants and foreground M stars, we detect 19 objects in emission in all three bands, and 8 objects in emission in Hα and [O III]. We compare the structural and photometric properties of the detected sources to Local Group dwarf galaxies and star-forming galaxies in the 11HUGS and SINGG surveys. We find no large population of outlying H II regions or undiscovered star-forming dwarfs in the M101 Group, as most sources (93 %) are consistent with being M101 outer disk H II regions. Only two sources were associated with other galaxies: a faint star-forming satellite of the background galaxy NGC 5486, and a faint outlying H II region near the M101 companion NGC 5474. We also find no narrowband emission associated with recently discovered ultradiffuse galaxies and starless H I clouds near M101. The lack of any hidden population of low luminosity star-forming dwarfs around M101 suggests a rather shallow faint end slope (as flat as α ∼ −1.0) for the star-forming luminosity function in the M101 Group. We discuss our results in the context of tidally-triggered star formation models and the interaction history of the M101 Group.

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Section: Discussionmentioning

confidence: 99%

Section: Structural Analysismentioning

confidence: 99%

Section: Photometric Analysismentioning

confidence: 99%

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A Deep Census of Outlying Star Formation in the M101 Group

Garner

Mihos

Harding

et al. 2021

ApJ

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“…We build the NGC 5474 model in a similar fashion, setting its disk scale length to h R,N5474 = 1.5 kpc and adding a central bulge with a bulge:disk mass ratio of 1:3, in rough accordance with the observed properties of the system (e.g., Bellazzini et al 2020). However, in reality NGC 5474's bulge is strangely offset from the cen-ter of its disk by ∼ 1 kpc (e.g., Rownd et al 1994;Pascale et al 2021), suggesting the galaxy is likely well out of equilibrium, and our attempts to match the observed kinematics of the galaxy proved problematic.…”

Section: Simulation Methodsmentioning

confidence: 99%

“…Meanwhile, Hubble imaging of the stellar populations in M101's NE Plume has revealed ∼ 300 Myr old post-starburst population (Mihos et al 2018), likely marking the time since M101's most recent interaction. These observations, coupled with deep HI mapping of the M101 system (Walter et al 2008;Mihos et al 2012;Xu et al 2021) and new imaging and spectroscopy of NGC 5474 (Bellazzini et al 2020) provide updated constraints on a potential interaction between M101 and NGC 5474. We use these new constraints to develop the first self-consistent N-body simulation of the M101/NGC 5474 encounter, explaining a wide variety of the observed properties while also giving insight into the subsequent evolution of M101's disk.…”

Section: Introductionmentioning

confidence: 99%

A Dynamical Model of the M101/NGC 5474 Encounter

Linden¹,

Mihos²

2022

ApJL

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We present the first dynamical simulation that recreates the major properties of the archetypal nearby spiral galaxy M101. Our model describes a grazing but relatively close (∼14 kpc) passage of the companion galaxy NGC 5474 through M101's outer disk approximately 200 Myr ago. The passage is retrograde for both disks, yielding a relatively strong gravitational response while suppressing the formation of long tidal tails. The simulation reproduces M101's overall lopsidedness, as well as the extended NE Plume and the sharp western edge of the galaxy’s disk. The post-starburst populations observed in M101's NE Plume are likely a result of star formation triggered at the point of contact where the galaxies collided. Over time, this material will mix azimuthally, leaving behind diffuse, kinematically coherent stellar streams in M101's outer disk. At late times after the encounter, the density profile of M101's disk shows a broken “upbending” profile similar to those seen in spiral galaxies in denser environments, further demonstrating the connection between interactions and long-term structural changes in galaxy disks.

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Massive black holes in nuclear star clusters

Hoyer,

Arcodia,

Bonoli

et al. 2024

A&A

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Context. Massive black holes (MBHs) are typically hosted in the centres of massive galaxies but they appear to become rarer in lower mass galaxies, where nuclear star clusters (NSCs) frequently appear instead. The transition region, where both an MBH and NSC can co-exist, has been poorly studied to date and only a few dozen galaxies are known to host them. One avenue for detecting new galaxies with both an MBH and NSC is to look for accretion signatures of MBHs. Aims. Here, we use new SRG/eROSITA all-sky survey eRASS:4 data to search for X-ray signatures of accreting MBHs in NSCs, while also investigating their combined occupation fraction. Methods. We collected more than 200 galaxies containing an NSC, spanning multiple orders in terms of galaxy stellar mass and morphological type, within the footprint of the German eROSITA Consortium survey. We determined the expected X-ray contamination from binary stellar systems using the galaxy stellar mass and star formation rate as estimated from far-ultraviolet and mid-infrared emission. Results. We find significant detections for 18 galaxies (~8.3%), including one ultra-luminous X-ray source; however, only three galaxies (NGC 2903, 4212, and 4639) have X-ray luminosities that are higher than the expected value from X-ray binaries, indicative of the presence of an MBH. In addition, the X-ray luminosity of six galaxies (NGC 2903, 3384, 4321, 4365, 4639, and 4701) differs from previous studies and could indicate the presence of a variable active galactic nucleus. For NGC 4701 specifically, we find a variation of X-ray flux within the eRASS:4 data set. Stacking X-ray non-detected galaxies in the dwarf regime M*gal ≤ 109 M⊙) results in luminosity upper limits of a few times 1038 erg s−1. The combined occupation fraction of accreting MBHs and NSCs becomes non-zero for galaxy masses above ~ 107.5 M⊙ and this result is slightly elevated as compared to the literature data. Conclusions. Our data extend, for the first time, towards the dwarf elliptical galaxy regime and identify promising MBH candidates for higher resolution follow-up observations. At most galaxy masses (and with the exception of three cases), the X-ray constraints are consistent with the expected emission from binary systems or an Eddington fraction of at most 0.01%, assuming a black holes mass of 106.5 M⊙. This work confirms the known complexities in similar-type of studies, while providing the appealing alternative of using X-ray survey data of in-depth observations of individual targets with higher resolution instruments.

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The strange case of the peculiar spiral galaxy NGC 5474

Cited by 10 publications

References 43 publications

A Deep Census of Outlying Star Formation in the M101 Group

A Deep Census of Outlying Star Formation in the M101 Group

A Dynamical Model of the M101/NGC 5474 Encounter

Massive black holes in nuclear star clusters

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