arXiv:1802.00031v2 [astro-ph.GA] 8 Feb 2018 G 25 ssrone yagatfiaetr emission- H filamentary with giant nebulae, a Such by . cluster, line surrounded is the 1275, of NGC galaxy dominant central The INTRODUCTION 1 MNRAS olcr lses(e.g. clusters core know cool Perseus, like distributions brightness surface X-ray ⋆ (heat ionization merger of source flow, and cooling gas) (residual dragged or nebulae accretion these gas of origin The kpc 80 over extends 1275 NGC in nebula filamentary 10 several n lse (e.g. cluster any p (3.8’ kpc .Gendron-Marsolais M. entirety its nebula in filamentary 1275 the NGC of in structure velocity the Revealing .McDonald M. n .Morrison G. and cetdXX eevdYY noiia omZZZ form original in YYY; Received XXX. Accepted c 1 2 3 4 5 6 7 8 9 10 ´ preetd hsqe nvri´ eMontr´eal, Montr Universit´e de Physique, D´epartement de ´ preetd hsqe egei hsqee d’optique, et g´enie physique de physique, D´epartement de eateto hsc n srnm,Uiest fHwi a Hawaii of University Astronomy, and Physics of Department al nttt o srpyisadSaeRsac,MT C MIT, Research, Space and Astrophysics for Institute Kavli nttt fAtooy nvriyo abig,Madingle Cambridge, of University Astronomy, of Institute etefrEtaaatcAtooy eateto Physics of Department Astronomy, Extragalactic for Centre RL bevtied yn NS nvri´ yn1 Aven 9 1, Universit´e Lyon CNRS, Lyon, de Observatoire CRAL, eateto hsc n srnm,Uiest fWaterlo of University Astronomy, and Physics of Department eiee nttt o hoeia hsc,Wtro,ON Waterloo, Physics, Theoretical for Institute Perimeter -al [email protected] E-mail: B bevtr,Uiest fAioa 3 .Cer v,R Ave, Cherry N. 933 Arizona, of University Observatory, LBT 07TeAuthors The 2017 000 × 42 .’ n steeoeaogtelretkonin known largest the among therefore is and 2.6’) erg , 1 – / 6 ,aentrr mn lseshvn peaked having clusters among rare not are s, coade l 2012 al. et McDonald 21)Pern 2Fbur 08Cmie sn NA L MNRAS using Compiled 2018 February 12 Preprint (2017) 4 .C Fabian C. A. , rwode l 1999 al. et Crawford 10 esrmnso h -a a yaisi esu r loexplor also b are Perseus fila nor words: in the galaxy, Key dynamics of the gas properties onto X-ray physical the the uniformly of between falling measurements Comparison not it. from are out filaments that dicating iprinpol hw eea eraewt nraigdistanc increasing with n decrease the to general across up source a and at shows mechanism ionization profile the dispersion in change a gesting n ore rnfr pcrmtrSTLEa FT ihiswide its With CFHT. t neb at with entire SITELLE nebula ( this spectrometer the of transform across component Fourier low-velocity gian structure gala ing the the brightest velocity of of cluster’s observations rich map new Perseus unknown velocity the detailed previously a 1275, a time NGC first surrounding the nebula for produced have We ABSTRACT oe h 0kpc 80 the cover bevtossosasot ailgain fte[ II] [N the of gradient radial smooth a shows observations ∼ 1 α 11’ ⋆ uioiisa ihas high as luminosities .Hlavacek-Larrondo J. , ; × ae ta.2016 al. et Hamer 1) IEL steol nerlfil ntsetocp instrumen spectroscopy unit field integral only the is SITELLE 11’), ∼ .Hwvr the However, ). 5 10 .C Edge C. A. , aais G 25-Glxe:cutr:idvda:Prescluster Perseus individual: clusters: : - 1275 NGC Galaxies: p.Tevlct a hw ovsbegnrltedo oain in- rotation, or trend general visible no shows map velocity The kpc. × 5kc(3.8’ kpc 55 e l(uee) CHC37 Canada 3J7, ´eal H3C (Qu´ebec), QC nvri´ aa,14 vned am´edecine, Qu´ebec la (Qu de avenue 1045 Universit´e Laval, × as n 2 Y,Canada 2Y5, N2L , od abig B H,UK 0HA, CB3 Cambridge Road, y 55 uhmUiest,Dra H L,UK 3LE, DH1 Durham University, Durham , ). mrde A019 USA 02139, MA ambridge, ,Wtro,O,NL31 Canada 3G1, N2L ON, Waterloo, o, io 0 aiiS. io I S 9672 USA HI, Hilo, St., Kawili W 200 Hilo, t o 5,Tco,A 52 U.S.A. 85721 AZ Tucson, 552, oom eCalsAd´,F651SitGnsLvl France Genis-Laval, Saint Andr´e, F-69561 Charles ue 6 × h lcrmgei pcrm eeln ait fstruc of variety a revealing spectrum, electromagnetic the X- the its in ( sky cluster with ray brightest interactions the by As nu affected environment. galactic surrounding externally active and its (AGN) of outbursts clei nuclear internally the both by environment, complex perturbed a in resides 1275 NGC and heat our shocks medium. for as surrounding research their such ionize of phenomena how area active of understanding an constitute therefore ulae eae osa omto steln aisaedffrn fro be different (e.g. to are regions ratios II appear H line not in the those as does formation source are ionization to mixing) related The turbulent clear. or yet shocks not ICM, the from conduction .L Hamer L. S. , .’ ag euai G 25 u nlsso these of analysis Our 1275. NGC in nebula large 2.6’) en h lse’ rgts aay(C)i Perseus, in (BCG) galaxy brightest cluster’s the Being 1 .B Martin B. T. , omne l 1972 al. et Forman 7 .McNamara B. , et&Sret1979 Sargent & Kent ,i a enosre cosall across observed been has it ), 2 λ .Drissen L. , 6583/H et n Hitomi and ments ed. α rmteAGN the from e y n revealed and xy, A l.W present We ula. eotclimag- optical he bl,wiethe while ebula, T ierto sug- ratio, line E e e) 1 A,Canada 0A6, ´ebec), G1V tl l v3.0 file style X filamentary t edo view of field .Teeneb- These ). 8 igpulled eing , 9 2 beto able t , 3 , m - - L2 M. Gendron-Marsolais et al. tures. X-ray observations of the (ICM) have shown a succession of cavities created by the jets of 1 arcmin =21.2 kpc

the central , pushing away the clus- 32:59.9 ter gas and leaving buoyantly rising bubbles filled with radio Northern filament

emission (e.g. Fabian et al. 2011). 23.9 Horseshoe -shaped filament First observed by Minkowski (1957) and Lynds (1970), 47.9 Tangential filament the nebula surrounding NGC 1275 consists of two distinct − components: a high-velocity system (∼ 8200 km s 1, HV) Declination Eastern corresponding to a foreground galaxy, and a low-velocity 41:31:11.9 filaments High-velocity − system system (∼ 5200 km s 1, LV) associated with NGC 1275. HST observations of the LV system have revealed a thread- 30:35.9 like filamentary composition, some only 70 pc wide and 6 kpc long (Fabian et al. 2008). The brighter filaments have 59.9 soft X-ray counterparts (Fabian et al. 2003) and Karl G. Southeast filament Arc

Jansky Very Large Array 230-470 MHz observations show 29:23.9 a spur of emission in the direction of the northern filament 57.6 55.2 52.8 50.4 3:19:48.0 45.6 43.2 40.8 38.4 Right ascension (Gendron-Marsolais et al. 2017). Cold molecular gas are as- sociated with some of the filaments, e.g. CO (Salom´eet al. Figure 1. Mean integrated flux SN3 filter image centered on 2006; Ho et al. 2009; Salom´eet al. 2011) and H2 (Lim et al. NGC 1275. The HV system and the different filaments of the LV 2012). system are identified. 2 DATA REDUCTION AND ANALYSIS The nebula was imaged by Conselice et al. (2001) in its NGC 1275 was observed in January 2016 with the opti- full extent with high-resolution imaging, integral field and cal imaging Fourier transform spectrometer SITELLE at long-slit spectroscopy (WIYN & KPNO). The authors pro- CFHT during Queued Service Observations 16BQ12 in sci- ′′ duced a first velocity map of the central ∼ 45 (16 kpc), ence verification mode (PI G. Morrison) with the SN3 fil- 90% revealing evidence for rotation, and suggested that the fil- ter (> transmission from 647-685 nm) for 2.14h (308 1800 aments were being formed through compression of the hot exposures of 25 seconds, R = ). SITELLE is a Michel- 11′ × 11′ ICM by the AGN outflows of NGC 1275. Further observa- son interferometer with a large field of view ( , 1′ × 1′ 8′′ × 8′′ tions from the Gemini Multi-Object Spectrograph along six compare to for MUSE and up to for SIN- 2048 × 2064 slits aligned with 2-3 filaments showed evidence of outflow- FONI) equipped with two E2V detectors of 0 321′′ × 0 321′′ ing gas and flow patterns (Hatch et al. 2006). Overall, this pixels, resulting in a spatial resolution of . . . suggests that these filamentary nebulae could be formed by These observations were centered at RA 03h19m53.19s and 41◦33′51 0′′ 3′ gas being dragged out from the rise of AGN radio bubbles DEC + . , offset by about from NGC 1275. in the ICM and stabilized by magnetic fields (Fabian et al. The data reduction and calibration of these observations were conducted using the SITELLE’s software ORCS (ver- 2003; Hatch et al. 2006; Fabian et al. 2008). This is further 1 supported by the presence of a horseshoe-shaped filament, sion 3.1.2, Martin et al. 2015 ). Five emission lines are re- λ α λ bending behind the North-West outer cavity, similarly to the solved in these observations: [N II] 6548, H , [N II] 6584, λ λ toroidal flow pattern trailing behind a buoyant gas bubble in [S II] 6716 and [S II] 6731. Details of the wavelength, a liquid. Under this assumption, the loop-like X-ray struc- astrometric and photometric calibration followed are de- ture extending at the end of the northern filament would scribed in Martin et al. (2018). The OH sky lines veloci- then be a fallback of gas dragged out to the north by previ- ties were fitted with an optical model of the interferome- ously formed bubbles (Fabian et al. 2011). However, the Hα ter in most regions of the cube with the function Spec- emission found in several cool core clusters’ BCGs is delim- tralCube.map sky velocity() and the resulting wave- ited within their cooling radius and a strong correlation has length corrections for instrumental flexures were applied been found between Hα luminosity and the X-ray cooling to the cube using SpectralCube.correct wavelength() flow rate of the host cluster (McDonald et al. 2010). This (Martin et al. 2018). The mean integrated flux SN3 filter im- suggests that the ionized gas may be linked to the ICM and age centered on NGC 1275 is shown on figure 1. a radially infalling cooling flow model is favoured. The complexity of this nebula arises from its several components: overlapping filaments with slightly different ve- locity shifts, the HV system and the AGN contribution. As NGC 1275 is one of the richest nebulae to study due we focus only on the LV component, pixels with [N II]λ6548, to its proximity and the complexity of its structures. In Hα and [N II]λ6584 emission lines with a velocity shift this article, we present new observations of NGC 1275 close to the NGC 1275 systemic velocity were identified. obtained with SITELLE, a new optical imaging Fourier The HV system was identified similarly, using a 8200 km/s transform spectrometer at Canada-France-Hawaii Telescope systemic velocity, and subtracted. Fitting both the contri- (CFHT). Unlike previous IFU observations of NGC 1275, ′ ′ bution from the AGN and the filaments, we found that the its wide field of view (11 × 11 ) covers the large neb- contribution from the AGN is predominant in terms of lines ula in its entirety. To directly compare our results with ′′ fluxes inside a radius of 6 . The central region centered at Hitomi Collaboration et al. (2017), we adopt a of z = 0.017284 for NGC 1275, corresponding to an angular −1 scale of 21.2 kpc arcmin . This corresponds to a luminos- 1 https://github.com/thomasorb/orcs −1 −1 ity distance of 75.5 Mpc, assuming H0 = 69.6 km s Mpc , ΩM = 0.286 and Ωvac = 0.714. MNRAS 000, 1–6 (2017) The filamentary nebula in NGC1275˜ L3

5.00e-16 2 200

Dispersion map ¡ H flux map [N II] 6583/Hα 2.38e-16 1.8 181

1.15e-16 1.5 162

5.85e-17 1.3 ¥ ¦ §

3.22e-17 1 1 £ ¤

2.01e-17 0.78 106

1.44e-17 0.53 87

1.18e-17 0.29 68

1.06e-17 0.043 4 ¢ 1’ = 21.2 kpc

1.00e-17 -0.2 30

Figure 2. Flux map of Hα emission in the LV system region (left, units are in erg/s/cm2/pixel), [N II]λ6583/Hα line ratio map (middle) and dispersion map (right, scale unit is in km/s). ′′ 3h19m48.1s + 41d30m42s with a radius of 6 was excluded.

To increase the SNR without losing too much spatial res- © 1.5 olution, we chose to bin the cube by a factor of 2. The 1.0 6583/H spectrum extracted from each binned remaining pixel was ¨ 0.5 fitted using a Gaussian function convolved with the instru- [NII] mental line shape - a sinc function (Martin et al. 2016). The fitting software uses a least-squares Levenberg-Marquardt 200 minimization algorithm (Levenberg 1944; Marquardt 1963)

Dispersion 0 to fit the data. We restricted the range of wavelengths to the band where [N II]λ6548, Hα and [N II]λ6584 lines are 400 found with the systemic velocity shift of NGC 1275. Sky sub- 200 traction was done using the mean flux from a circular region 0 ′′ Velocity with a radius of 20 centered at RA 03h19m58.57s and DEC ◦ ′ ′′ ′ 200 +41 30 08.9 , about 2 south-east of NGC 1275 nucleus. The 10kpc 20 30 40 lines were fitted simultaneously, the velocity and broadening Figure 3. The mean (in red, with error bars indicating the stan- of the three lines grouped to reduce the number of parame- dard deviation) and ensemble fit result (in blue) [N II]λ6583/Hα α 30 × ters to fit. Only pixels with fitted H flux higher than line ratio, dispersion and velocity profiles taken in annuli contain- −18 2 10 erg/s/cm /pixel were selected. To directly compare our ing 400 pixels centred on the AGN. Dispersions and velocities are results with Hitomi Collaboration et al. (2017), bulk veloc- given in km/s and the distance from the AGN is in kpc. ities are calculated with respect to their redshift measure- −1 ment: vbulk ≡ (z−0.017284)∗c0 −21.9km s , where c0 is the −1 speed of light and −21.9km s is the heliocentric correction based on the average value over the observation period from the mean and ensemble ratio profiles taken in annuli con- Astropy SkyCoord.radial velocity correction(). taining 400 pixels is shown on figure 3. The line ratio varies through the map, being ∼ 0.5 − 1 in the extended filaments, 3 RESULTS AND DISCUSSION and above 1 in the central part of the nebula. However, 3.1 Ionization mechanism streaks of star forming clusters associated with some fila- Figure 2 (left) shows the Hα flux map. While the surface ments of NGC 1275 have been found (Canning et al. 2014). brightness of Hα is mostly constant in the extended fila- Similar line ratio gradients have also been previously ob- ′′ ments, it is higher in the inner ∼ 30 = 11kpc. served in the filaments of NGC 1275 (Hatch et al. 2006) and Optical line ratios can be good indicators of the dom- in several BCG with optical line emission (e.g. Hamer et al. inant excitation mechanism operating on the line-emitting 2016). The central region with higher line ratios could be gas (photoionization by , by a power-law continuum related to energetic sources of ionization such as AGN and source or shock-wave heating, Baldwin et al. 1981) . The ra- shocks, while filaments must be ionized by a source with tio [N II]λ6583/Hα provides, for example, a measure of the lower power. To effectively distinguished the source of ion- ionization state of a gas. When the source of ionization is ization though, other line ratios are required, falling outside stellar formation, this line ratio is a linear function of metal- of the filter used during these observations. The complete licity saturating at a value of ∼ 0.5 for high (e.g. detailed BPT diagnostic of NGC 1275 nebula will be con- Kewley et al. 2006). The SITELLE [N II]λ6583/Hα line ra- ducted using awarded SITELLE observations at 365-385 nm tio map of NGC 1275 is presented in figure 2 (middle) and and 480-520 nm (PI: Gendron-Marsolais) and presented in future work (Gendron-Marsolais et al. in prep.). MNRAS 000, 1–6 (2017) L4 M. Gendron-Marsolais et al.

Table 1. Comparison between Hitomi and Sitelle best-fitted bulk velocities and dispersions in regions shown on Figure 4 1’ =22.5 kpc Hitomi SITELLE Region vbulk (km/s) σv (km/s) vbulk (km/s) σv (km/s)

Reg 3 Reg 4 +26 +19 Reg 0 75−28 189−18 48 ± 3 145 ± 3 +19 +19 Reg 1 46−19 103−20 −8 ± 9 155 ± 9

Reg 1 +14 +17 Reg 2 47−14 98−17 182 ± 2 116 ± 3 +15 +20 Reg 3 −39−16 106−20 122 ± 2 94 ± 2 +29 +21 Reg 4 −77−28 218−21 182 ± 3 88 ± 3 Reg 0

Reg 2

1' = 22.5 kpc

300 Figure 4. Chandra composite fractional residual image from Fabian et al. (2011) in the 0.5-7 keV band (1.4 Ms exposure). The PSF corrected Hitomi regions from Hitomi Collaboration et al. (2017) are shown in white. Contours from the LV system Hα flux 200 map (starting at 3 × 10−17 erg/s/cm2/pixel) are shown in green.

100

3.2 Velocity dispersion measure across the nebula According to the top-down multiphase condensation model, 0 warm filaments and cold molecular clouds condensed out of the hot ICM through ”chaotic cold accretion” (e.g. Gaspari et al. 2017b). This link between ICM and filaments -100 imply that both must have the same ensemble velocity dis- persion. On the other hand, if these filaments are rather dragged out from the rise of AGN radio bubbles, they would -200 be stabilized into the hot gas by magnetic fields, and there- fore also sharing the same velocity field (Fabian et al. 2008). The Hitomi Soft X-ray Spectrometer has shown that the line-of-sight velocity dispersions are on the order of 164±10 30 − 60 Figure 5. The velocity map of the LV system (in km/s). Profiles km/s in the kpc region around the nucleus of the extracted from the three white regions are shown in figure 6. Perseus cluster (Hitomi collaboration 2016), while SITELLE has provided an ensemble line-of-sight velocity dispersion of 3.3 Kinematics of the filaments 137 ± 20 km/s (Gaspari et al. 2017a). In contrast, the dis- The velocity map of the LV system (see Figure 5) reveals a persion map obtained from the fitting of each binned pixel previously unknown rich velocity structure across the entire shown in figure 2 shows instead smaller velocity dispersion in nebula. The presence of a larger scale velocity gradient is the filaments (. 115 km/s), but increasing linewidth closer hard to extract from such a detailed map. We note that the to the center (up to ∼ 130 km/s). SITELLE’s level of res- median heliocentric velocity of the map is 5229 km/s, giving olution therefore probes smaller structures like individual a high fraction of redshifted pixels (∼ 80%) relative to our filaments, rather than the ensemble multiphase gas. Interest- chosen rest frame. We will discuss this difference in future ingly, the mean and ensemble dispersion profiles in figure 3 work (Gendron-Marsolais et al. in prep.). Overall, the mean show a general decrease up to ∼ 10 kpc from the nucleus but and ensemble velocity profiles from figure 3 do not show any a bump is visible between ∼ 15−20 kpc. This corresponds to clear radial gradient in velocity. On average, the filaments the region between the inner and ghost cavities and contains do not seem to be falling smoothly and uniformly onto the a known shock in the ICM to the north-east (Fabian et al. galaxy nor do they seem to be pulled out of it. No potential 2006) which could be responsible for the higher mean dis- rotation, as suggested in Conselice et al. (2001), is visible. persion. The lack of ordered motion and the low measured velocities Further comparisons can be explored between Hitomi might indicate that these features are short lived, consistent and Sitelle line-of-sight velocity dispersions in the same re- with the molecular gas (e.g. Russell et al. 2016). gions as the ones used in Hitomi Collaboration et al. (2017) With the spectral and spatial resolution provided by and shown in Figure 4. SITELLE pixels contained in each SITELLE, the kinematics of the filaments can be studied of those regions with Hα and [N II] lines (including the individually. The line-of-sight velocity structure across the AGN but excluding the HV system) were fitted as ensembles northern filament is very complex. Velocities from each pixel (see Table 1). The resulting velocities dispersions are as low are plot against their distance from the AGN in figure 6 and (∼ 120 km/s) and uniform as the Hitomi measurements for show a scattered profile. The mean velocity profile taken the hot gas, supporting the infalling cooling flow model. MNRAS 000, 1–6 (2017) The filamentary nebula in NGC1275˜ L5

(iii) The velocity map of NGC 1275 revealed by SITELLE

00 shows a previously unknown rich velocity structure across the entire nebula with no clear general trend or potential

0 rotation, indicating that filaments are not falling uniformly onto the galaxy, nor being pulled out from it. 00 These results demonstrate how SITELLE, with its large field 0 0 0 0 of view, high angular and spectral resolution, is well suited for the study of emission-line nebulae among clusters’ BCGs. 00 ACKNOWLEDGMENTS 0 MLGM is supported by the NSERC Postgraduate 00 Scholarships-Doctoral Program. JHL and LD are supported 0 0 by NSERC through the discovery grant and Canada Re- search Chair programs, as well as FRQNT. ACF acknowl- 00 edges ERC Adanced Grant 340442. ACE acknowledges sup- 0 port from STFC grant ST/P00541/1. Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) 00

which is operated from the summit of Maunakea by the Na- 0 tional Research Council of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Figure 6. Velocity profiles extracted from the three white regions Scientifique of France, and the University of Hawaii. The ob- on figure 5 (in km/s). In the velocity profiles across the northern and the southeast filaments, velocities from each pixel are in blue servations at the Canada-France-Hawaii Telescope were per- while the mean taken in ten bins of equal width are shown in red. formed with care and respect from the summit of Maunakea These are plot against their distance from the base of the filaments which is a significant cultural and historic site. (in kpc). A velocity profile across the horseshoe filament is also shown, the mean of the fitted velocities taken from ten bins. REFERENCES in ten bins of equal width shows a more general trend, Baldwin J. A., Phillips M. M., Terlevich R., 1981, PASP, 93, 5 varying from positive to negative velocity as the radial dis- Canning R. E. A., et al., 2014, MNRAS, 444, 336 tance to the nuclei increase. This is consistent with Gemini Conselice C. J., Gallagher III J. S., Wyse R. F. G., 2001, ApJ, Multi-Object Spectrograph observations along this filament 122, 2281 Crawford C. S., Allen S. W., Ebeling H., Edge A. C., Fabian (Hatch et al. 2006). The northern filament is therefore ei- A. C., 1999, MNRAS, 306, 857 ther stretching or collapsing depending on its de-projected Fabian A. C., Sanders J. S., Crawford C. S., Conselice C. J., orientation. Furthermore, the southeast filament also shows Gallagher J. S., Wyse R. F. G., 2003, MNRAS, 344, L48 complex dynamics with a mostly negative line-of-sight veloc- Fabian A. C., Sanders J. S., Taylor G. B., Allen S. W., Crawford ity, varying from ∼ −100 km/s to −300 km/s and increasing C. S., Johnstone R. M., Iwasawa K., 2006, MNRAS, 366, 417 again up to ∼ 0 km/s as the distance from the center increase Fabian A. C., Johnstone R. M., Sanders J. S., Conselice C. J., (see figure 6). Finally, the mean velocity profile across the Crawford C. S., Iii J. S. G., Zweibel E., 2008, Nature, 454, horseshoe-shaped filament extracted from then bins is shown 968 on figure 6. It has an overall positive velocity increasing al- Fabian A. C., et al., 2011, MNRAS, 418, 2154 most symmetrically on either side of the loop, reaching ve- Forman W., Kellogg E., Gursky H., Tananbaum H., Giacconi R., 1972, ApJ, 178, 309 locities of ∼ 200 km/s. Again, this is similar to Hatch et al. Gaspari M., et al., 2017a, accepted in ApJ, arXiv:1709.06564 (2006) results and consistent with simulations of flow pat- Gaspari M., Temi P., Brighenti F., 2017b, MNRAS, 466, 677 terns below a rising bubble where the gas flows down on Gendron-Marsolais M., et al., 2017, MNRAS, 469, 3872 either sides of the bubble, the highest velocities located just Hamer S. L., et al., 2016, MNRAS, 460, 1758 behind the bubble. Table 1 shows the comparisons between Hatch N. A., Crawford C. S., Fabian A. C., Johnstone R. M., Hitomi and Sitelle best-fitted bulk velocities. Contrary to 2006, MNRAS, 367, 433 the velocity dispersions, we see no correlations between the Hitomi Collaboration et al., 2017, arXiv:1711.00240 bulk velocities of the warm and ionized gas, except for Reg Hitomi collaboration ., 2016, Nature, 535, 117 0. Ho I.-T., Lim J., Dinh-V-Trung 2009, ApJ, 698, 1191 4 CONCLUSION Kent S. M., Sargent W. L. W., 1979, ApJ, 230, 667 Kewley L. J., Groves B., Kauffmann G., Heckman T., 2006, We have used SITELLE observations to probe the detailed MNRAS, 372, 961 dynamics of the filamentary nebula surrounding NGC 1275. Levenberg K., 1944, Quart. Appl. Math., 2, 164 (i) We observe a smooth radial gradient of the [N Lim J., Ohyama Y., Chi-Hung Y., Dinh-V-Trung Shiang-Yu W., II]λ6583/Hα line ratio, suggesting a change in the ionization 2012, ApJ, 744, 112 mechanism and source across the nebula: higher line ratios Lynds R., 1970, ApJL, 159 are found in the central region and must therefore be related Marquardt D. W., 1963, SIAM J Appl Math, 11, 431 Martin T., Drissen L., Joncas G., 2015. ADASS XXIV, p. 327 to energetic sources of ionization (AGN and shocks), while Martin T. B., Prunet S., Drissen L., 2016, MNRAS, 463, 4223 filaments must be ionized by a source with lower power. Martin T. B., Drissen L., Melchior A.-L., 2018, MNRAS, 473, (ii) The velocity dispersions decrease with increasing dis- 4130 tance from the center, but are as low and uniform as the McDonald M., Veilleux S., Rupke D. S. N., Mushotzky R., 2010, Hitomi measurements of the ICM, while we see no correla- ApJ, 721, 1262 tions between the warm and the ionized gas bulk velocities. McDonald M., Veilleux S., Rupke D. S. N., 2012, ApJ, 746, 153

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MNRAS 000, 1–6 (2017)