Confirmation of Faint Dwarf Galaxies in the M81 Group

Chiboucas, Kristin; Jacobs, B.A. onder red. van E.; Tully, R. Brent; Караченцев, И. Д.

doi:10.1088/0004-6256/146/5/126

Cited by 189 publications

(209 citation statements)

References 73 publications

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“…They are easily exposed to the sweep-out of gas from their shallow potential wells. A special search for such ultra-dwarfs in the vicinity of M 81 (Chiboucas et al 2009(Chiboucas et al , 2013 confirms that they are dominated by quenching objects with no signs of star formation (Kaisin & Karachentsev 2013). …”

Section: Segregation Of Companions By Morphological Typesmentioning

confidence: 86%

Companions around the nearest luminous galaxies: Segregation and selection effects

Караченцев

Kudrya

2015

Astron Nachr

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Using the "Updated Nearby Galaxy Catalog", we consider different properties of companion galaxies around luminous hosts in the Local Volume. The data on stellar masses, linear diameters, surface brightnesses, HI-richness, specific star formation rate (sSF R), and morphological types are discussed for members of the nearest groups, including the Milky Way and M 31 groups, as a function of their separation from the hosts. Companion galaxies in groups tend to have lower stellar masses, smaller linear diameters and fainter mean surface brightnesses as the distance to their host decreases. The hydrogen-to-stellar mass ratio of the companions increases with their linear projected separation from the dominant luminous galaxy. This tendency is more expressed around the bulge-dominated hosts. While linear separation of the companions decreases, their mean sSF R becomes lower, accompanied with the increasing sSF R scatter. Typical linear projected separation of dSphs around the bulge-dominated hosts, 350 kpc, is substantially larger than that around the disk-dominated ones, 130 kpc. This difference probably indicates the presence of larger hot/warm gas haloes around the early-type host galaxies. The mean fraction of dSph (quenched) companions in 11 the nearest groups as a function of their projected separation Rp can be expressed as f (E) = 0.55 − 0.69 × Rp. The fraction of dSphs around the Milky Way and M 31 looks much higher than in other nearby groups because the quenching efficiency dramatically increases towards the ultra-low mass companions. We emphasize that the observed properties of the Local Group are not typical for other groups in the Local Volume due to the role of selection effects caused by our location inside the Local Group.

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Section: Segregation Of Companions By Morphological Typesmentioning

confidence: 86%

Companions around the nearest luminous galaxies: Segregation and selection effects

Караченцев

Kudrya

2015

Astron Nachr

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“…We will apply this same technique to the newly discovered dwarf satellites of M81 located at ∼3.8 Mpc (Chiboucas et al 2009(Chiboucas et al , 2013 and to the dwarf galaxies and streams that Figure 8. Metallicity-luminosity relation for dwarf galaxies.…”

Section: Discussionmentioning

confidence: 99%

“…Thus, it is important to make a systematic study of these faint structures beyond the Local Group and understand whether these inconsistencies between ΛCDM and observations are a consequence of the Local Group being an outlier or whether some of the physics considered in these simulations needs to be adjusted. Some efforts have begun in this direction (Chiboucas et al 2009(Chiboucas et al , 2013Crnojević et al 2014;Sand et al 2014;Toloba et al 2016), but they are generally limited to photometric information. Spectroscopy of these faint structures and satellites provides dynamical information to model the disruptive events and predict their timescales as well as information on stellar metallicity to learn about their star formation histories.…”

Section: Introductionmentioning

confidence: 99%

New Spectroscopic Technique Based on Coaddition of Surface Brightness Fluctuations: NGC 4449 and Its Stellar Tidal Stream

Toloba

Guhathakurta

Romanowsky

et al. 2016

ApJ

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We present a new spectroscopic technique based in part on targeting the upward fluctuations of the surface brightness for studying the internal stellar kinematics and metallicities of galaxies of low surface brightness effects both to galaxies and streams beyond the Local Group. The distance to these systems makes them unsuitable for targeting individual red giant branch (RGB) stars (tip of RGB at  I 24 mag) and their surface brightness is too low (  m 25 r mag arcsec −2 ) for integrated light spectroscopic measurements. This technique overcomes these two problems by targeting individual objects that are brighter than the tip of the RGB. We apply this technique to the star-forming dwarf galaxy NGC 4449 and its stellar stream. We use Keck/DEIMOS data to measure the line-ofsight radial velocity out to ∼7 kpc in the east side of the galaxy and ∼8 kpc along the stream. We find that the two systems are likely gravitationally bound to each other and have heliocentric radial velocities of 227.3 ± 10.7 km s −1 and 225.8 ± 16.0 km s −1 , respectively. Neither the stream nor the near half of the galaxy shows a significant velocity gradient. We estimate the stellar metallicity of the stream based on the equivalent width of its calcium triplet lines and find [Fe/H] = - 1.37 0.41, which is consistent with the metallicity-luminosity relation for dwarf galaxies in the Local Group. Whether the streamʼs progenitor was moderately or severely stripped cannot be constrained with this uncertainty in metallicity. We demonstrate that this new technique can be used to measure the kinematics and (possibly) the metallicity of the numerous faint satellites and stellar streams in the halos of nearby (∼4 Mpc) galaxies.

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“…This is the first of a series of papers in which we will analyze the dynamical and metallicity properties of dwarf galaxies and streams that reside in the halos of massive galaxies beyond the Local Group. The spectroscopic subject of this paper is d0944+71, which was discovered by Chiboucas et al (2009) during a CFHT search for faint dwarf galaxies around M81, and was subsequently confirmed to be at the distance of M81 (D = 3.63 Mpc; Karachentsev et al 2002) with followup Hubble Space Telescope observations (Chiboucas et al 2013). We present several previously known physical properties of d0944+71 in Table 1; it has an absolute magnitude of M I =−13.2, is gas poor (M HI <3.1×10 5 M ⊙ ; Roychowdhury et al 2012), and lies at a projected distance of 335 kpc from M81 itself.…”

Section: Introductionmentioning

confidence: 93%

“…We used the color-magnitude diagram (CMD) based on HST/ACS photometry to select point-like objects that are consistent with being stars in the recently discovered dwarf galaxy d0944+71 in the halo of M81. We selected the closest stars to the tip of the red giant branch (F 814W T RGB =23.77, extinction corrected; Chiboucas et al 2013) as spectroscopic targets. Due to the high density of stars, not all the potential targets were observable.…”

Section: Introductionmentioning

confidence: 99%

SPECTROSCOPIC CONFIRMATION OF THE DWARF SPHEROIDAL GALAXY d0994+71 AS A MEMBER OF THE M81 GROUP OF GALAXIES

Toloba

Sand

Guhathakurta

et al. 2016

ApJL

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We use Keck/DEIMOS spectroscopy to measure the first velocity and metallicity of a dwarf spheroidal (dSph) galaxy beyond the Local Group using resolved stars. Our target, d0944+71, is a faint dSph found in the halo of the massive spiral galaxy M81 by Chiboucas et al. We coadd the spectra of 27 individual stars and measure a heliocentric radial velocity of −38 ± 10 km s −1 . This velocity is consistent with d0944+71 being gravitationally bound to M81. We coadd the spectra of the 23 stars that are consistent with being red giant branch stars and measure an overall metallicity of [Fe/H] = −1.3 ± 0.3 based on the calcium triplet lines. This metallicity is consistent with d0944+71 following the metallicity−luminosity relation for Local Group dSphs. We investigate several potential sources of observational bias but find that our sample of targeted stars is representative of the metallicity distribution function of d0944+71 and any stellar contamination due to seeing effects is negligible. The low ellipticity of the galaxy and its position in the metallicity−luminosity relation suggest that d0944+71 has not been affected by strong tidal stripping.

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Confirmation of Faint Dwarf Galaxies in the M81 Group

Cited by 189 publications

References 73 publications

Companions around the nearest luminous galaxies: Segregation and selection effects

Companions around the nearest luminous galaxies: Segregation and selection effects

New Spectroscopic Technique Based on Coaddition of Surface Brightness Fluctuations: NGC 4449 and Its Stellar Tidal Stream

SPECTROSCOPIC CONFIRMATION OF THE DWARF SPHEROIDAL GALAXY d0994+71 AS A MEMBER OF THE M81 GROUP OF GALAXIES

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