The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Nicolas F Martin - One of the best experts on this subject based on the ideXlab platform.

  • the large scale structure of the halo of the Andromeda galaxy ii hierarchical structure in the pan Andromeda archaeological survey
    arXiv: Astrophysics of Galaxies, 2018
    Co-Authors: Alan W Mcconnachie, Mike Irwin, Nicolas F Martin, Annette M N Ferguson, Rodrigo A Ibata, Dougal A Mackey, Geraint F Lewis, Michelle L M Collins, Stephen D J Gwyn, T J Davidge
    Abstract:

    The Pan-Andromeda Archaeological Survey is a survey of $>400$ square degrees centered on the Andromeda (M31) and Triangulum (M33) galaxies that has provided the most extensive panorama of a $L_\star$ galaxy group to large projected galactocentric radii. Here, we collate and summarise the current status of our knowledge of the substructures in the stellar halo of M31, and discuss connections between these features. We estimate that the 13 most distinctive substructures were produced by at least 5 different accretion events, all in the last 3 or 4 Gyrs. We suggest that a few of the substructures furthest from M31 may be shells from a single accretion event. We calculate the luminosities of some prominent substructures for which previous estimates were not available, and we estimate the stellar mass budget of the outer halo of M31. We revisit the problem of quantifying the properties of a highly structured dataset; specifically, we use the OPTICS clustering algorithm to quantify the hierarchical structure of M31's stellar halo, and identify three new faint structures. M31's halo, in projection, appears to be dominated by two `mega-structures', that can be considered as the two most significant branches of a merger tree produced by breaking M31's stellar halo into smaller and smaller structures based on the stellar spatial clustering. We conclude that OPTICS is a powerful algorithm that could be used in any astronomical application involving the hierarchical clustering of points. The publication of this article coincides with the public release of all PAndAS data products.

  • comparing the observable properties of dwarf galaxies on and off the Andromeda plane
    The Astrophysical Journal, 2015
    Co-Authors: Alan W Mcconnachie, Nicolas F Martin, Annette M N Ferguson, Rodrigo A Ibata, S C Chapman, Michelle L M Collins, R M Rich, Michael J Irwin, Geraint F Lewis
    Abstract:

    The thin, extended planes of satellite galaxies detected around both the Milky Way and Andromeda are not a natural prediction of the Λ-cold dark matter paradigm. Galaxies in these distinct planes may have formed and evolved in a different way (e.g., tidally) from their off-plane neighbors. If this were the case, one would expect the on- and off-plane dwarf galaxies in Andromeda to have experienced different evolutionary histories, which should be reflected by the chemistries, dynamics, and star formation histories of the two populations. In this work, we present new, robust kinematic observations for two on-plane M31 dwarf spheroidal galaxies (And XVI and XVII) and compile and compare all available observational metrics for the on- and off-plane dwarfs to search for a signal that would corroborate such a hypothesis. We find that, barring their spatial alignment, the on- and off-plane Andromeda dwarf galaxies are indistinguishable from one another, arguing against vastly different formative and evolutionary histories for these two populations.

  • comparing the observable properties of dwarf galaxies on and off the Andromeda plane
    arXiv: Astrophysics of Galaxies, 2014
    Co-Authors: Alan W Mcconnachie, Nicolas F Martin, Annette M N Ferguson, Rodrigo A Ibata, S C Chapman, Michelle L M Collins, R M Rich, Michael J Irwin, Geraint F Lewis
    Abstract:

    The thin, extended planes of satellite galaxies detected around both the Milky Way and Andromeda are not a natural prediction of the LCDM paradigm. Galaxies in these distinct planes may have formed and evolved in a different way (e.g., tidally) to their off-plane neighbours. If this were the case, one would expect the on- and off-plane dwarf galaxies in Andromeda to have experienced different evolutionary histories, which should be reflected by the chemistries, dynamics, and star formation histories of the two populations. In this work, we present new, robust kinematic observations for 2 on-plane M31 dSphs (And XVI and XVII) and compile and compare all available observational metrics for the on- and off-plane dwarfs to search for a signal that would corroborate such a hypothesis. We find that, barring their spatial alignment, the on- and off-plane Andromeda dwarf galaxies are indistinguishable from one another, arguing against vastly different formative and evolutionary histories for these two populations.

  • the pandas field of streams stellar structures in the milky way halo toward Andromeda and triangulum
    The Astrophysical Journal, 2014
    Co-Authors: Nicolas F Martin, Alan W Mcconnachie, Rodrigo A Ibata, Arif Babul, Mark A Fardal, Michael R Rich, Geraint F Lewis, Michelle L M Collins, Michael J Irwin, N F Bate
    Abstract:

    We reveal the highly structured nature of the Milky Way (MW) stellar halo within the footprint of the Pan-Andromeda Archaeological Survey (PAndAS) photometric survey from blue main sequence (MS) and MS turn-off stars. We map no fewer than five stellar structures within a heliocentric range of ∼5-30 kpc. Some of these are known (the Monoceros Ring, the Pisces/Triangulum globular cluster stream), but we also uncover three well-defined stellar structures that could be, at least partly, responsible for the so-called Triangulum/Andromeda and Triangulum/Andromeda 2 features. In particular, we trace a new faint stellar stream located at a heliocentric distance of ∼17 kpc. With a surface brightness of Σ {sub V} ∼ 32-32.5 mag arcsec{sup –2}, it follows an orbit that is almost parallel to the Galactic plane north of M31 and has so far eluded surveys of the MW halo as these tend to steer away from regions dominated by the Galactic disk. Investigating our follow-up spectroscopic observations of PAndAS, we serendipitously uncover a radial velocity signature from stars that have colors and magnitudes compatible with the stream. From the velocity of eight likely member stars, we show that this stellar structure is dynamically cold, with an unresolved velocity dispersion thatmore » is lower than 7.1 km s{sup –1} at the 90% confidence level. Along with the width of the stream (300-650 pc), its dynamics point to a dwarf-galaxy-accretion origin. The numerous stellar structures we can map in the MW stellar halo between 5 and 30 kpc and their varying morphology is a testament to the complex nature of the stellar halo at these intermediate distances.« less

  • perseus i a distant satellite dwarf galaxy of Andromeda
    The Astrophysical Journal, 2013
    Co-Authors: Eric F Bell, Hanswalter Rix, Nicolas F Martin, Annette M N Ferguson, Colin T Slater, Edward F Schlafly, Edouard J Bernard, Douglas P Finkbeiner, Benjamin P M Laevens
    Abstract:

    We present the discovery of a new dwarf galaxy, Perseus I/Andromeda XXXIII, found in the vicinity of Andromeda (M31) in stacked imaging data from the Pan-STARRS1 3π survey. Located 27.°9 away from M31, Perseus I has a heliocentric distance of 785 ± 65 kpc, compatible with it being a satellite of M31 at from its host. The properties of Perseus I are typical for a reasonably bright dwarf galaxy (MV = –10.3 ± 0.7), with an exponential half-light radius of rh = 1.7 ± 0.4 arcmin or at this distance, and a moderate ellipticity (). The late discovery of Perseus I is due to its fairly low surface brightness ( mag arcsec–2), and to the previous lack of deep, high quality photometric data in this region. If confirmed to be a companion of M31, the location of Perseus I, far east from its host, could place interesting constraints on the bulk motion of the satellite system of M31.

Alan W Mcconnachie - One of the best experts on this subject based on the ideXlab platform.

  • the proper motion of Andromeda from gaia edr3 confirming a nearly radial orbit
    Monthly Notices of the Royal Astronomical Society, 2021
    Co-Authors: Alan W Mcconnachie, Rodrigo A Ibata, Jb Salomon, C Reyle, Benoit Famaey, Noam I Libeskind, Yehuda Hoffman
    Abstract:

    We present an analysis of the proper motion of the Andromeda galaxy (M31), based on the Early Third Data Release of the {\it Gaia} mission. We use the {\it Gaia} photometry to select young blue main sequence stars, and apply several quality cuts to obtain clean samples of these tracers. After correcting the proper motion measurements for the internal rotation of the M31 disk motion, we derive an apparent motion of $53.6 \pm 7.7 \, \mu as/yr$ with respect to the {\it Gaia} reference frame, or $62.0 \pm 9.6 \, \mu as/yr$ after applying a zero-point correction determined from quasars within $20\deg$ from M31. Accounting for the Solar reflex motion we deduce a relative velocity between Andromeda and the Milky way (in a non-rotating frame at the current location of the Sun) of $46.7 \pm 40.8 \, {\rm km.s^{-1}}$, (along right ascension) and $-64.7 \pm 31.7 \, {\rm km.s^{-1}}$ (along declination), with a total transverse velocity of $V_{\rm trans} = 79.8 \pm 38.3 \, {\rm km.s^{-1}}$. These values are consistent with (but more accurate than) earlier Hubble Space Telescope measurements that predict future merger between the two galaxies. We also note a surprisingly large difference in the derived proper motion between the blue stars in M31 and samples of red stars that appear to lie in that galaxy. We suspect that this is due to contamination from a foreground stellar stream.

  • the large scale structure of the halo of the Andromeda galaxy ii hierarchical structure in the pan Andromeda archaeological survey
    arXiv: Astrophysics of Galaxies, 2018
    Co-Authors: Alan W Mcconnachie, Mike Irwin, Nicolas F Martin, Annette M N Ferguson, Rodrigo A Ibata, Dougal A Mackey, Geraint F Lewis, Michelle L M Collins, Stephen D J Gwyn, T J Davidge
    Abstract:

    The Pan-Andromeda Archaeological Survey is a survey of $>400$ square degrees centered on the Andromeda (M31) and Triangulum (M33) galaxies that has provided the most extensive panorama of a $L_\star$ galaxy group to large projected galactocentric radii. Here, we collate and summarise the current status of our knowledge of the substructures in the stellar halo of M31, and discuss connections between these features. We estimate that the 13 most distinctive substructures were produced by at least 5 different accretion events, all in the last 3 or 4 Gyrs. We suggest that a few of the substructures furthest from M31 may be shells from a single accretion event. We calculate the luminosities of some prominent substructures for which previous estimates were not available, and we estimate the stellar mass budget of the outer halo of M31. We revisit the problem of quantifying the properties of a highly structured dataset; specifically, we use the OPTICS clustering algorithm to quantify the hierarchical structure of M31's stellar halo, and identify three new faint structures. M31's halo, in projection, appears to be dominated by two `mega-structures', that can be considered as the two most significant branches of a merger tree produced by breaking M31's stellar halo into smaller and smaller structures based on the stellar spatial clustering. We conclude that OPTICS is a powerful algorithm that could be used in any astronomical application involving the hierarchical clustering of points. The publication of this article coincides with the public release of all PAndAS data products.

  • comparing the observable properties of dwarf galaxies on and off the Andromeda plane
    The Astrophysical Journal, 2015
    Co-Authors: Alan W Mcconnachie, Nicolas F Martin, Annette M N Ferguson, Rodrigo A Ibata, S C Chapman, Michelle L M Collins, R M Rich, Michael J Irwin, Geraint F Lewis
    Abstract:

    The thin, extended planes of satellite galaxies detected around both the Milky Way and Andromeda are not a natural prediction of the Λ-cold dark matter paradigm. Galaxies in these distinct planes may have formed and evolved in a different way (e.g., tidally) from their off-plane neighbors. If this were the case, one would expect the on- and off-plane dwarf galaxies in Andromeda to have experienced different evolutionary histories, which should be reflected by the chemistries, dynamics, and star formation histories of the two populations. In this work, we present new, robust kinematic observations for two on-plane M31 dwarf spheroidal galaxies (And XVI and XVII) and compile and compare all available observational metrics for the on- and off-plane dwarfs to search for a signal that would corroborate such a hypothesis. We find that, barring their spatial alignment, the on- and off-plane Andromeda dwarf galaxies are indistinguishable from one another, arguing against vastly different formative and evolutionary histories for these two populations.

  • comparing the observable properties of dwarf galaxies on and off the Andromeda plane
    arXiv: Astrophysics of Galaxies, 2014
    Co-Authors: Alan W Mcconnachie, Nicolas F Martin, Annette M N Ferguson, Rodrigo A Ibata, S C Chapman, Michelle L M Collins, R M Rich, Michael J Irwin, Geraint F Lewis
    Abstract:

    The thin, extended planes of satellite galaxies detected around both the Milky Way and Andromeda are not a natural prediction of the LCDM paradigm. Galaxies in these distinct planes may have formed and evolved in a different way (e.g., tidally) to their off-plane neighbours. If this were the case, one would expect the on- and off-plane dwarf galaxies in Andromeda to have experienced different evolutionary histories, which should be reflected by the chemistries, dynamics, and star formation histories of the two populations. In this work, we present new, robust kinematic observations for 2 on-plane M31 dSphs (And XVI and XVII) and compile and compare all available observational metrics for the on- and off-plane dwarfs to search for a signal that would corroborate such a hypothesis. We find that, barring their spatial alignment, the on- and off-plane Andromeda dwarf galaxies are indistinguishable from one another, arguing against vastly different formative and evolutionary histories for these two populations.

  • comparing m31 and milky way satellites the extended star formation histories of Andromeda ii and Andromeda xvi
    The Astrophysical Journal, 2014
    Co-Authors: Alan W Mcconnachie, Andrew E Dolphin, Evan D Skillman, M Monelli, Daniel R Weisz, Sebastian L Hidalgo, Edouard J Bernard
    Abstract:

    We present the first comparison between the lifetime star formation histories (SFHs) of M31 and Milky Way (MW) satellites. Using the Advanced Camera for Surveys on board the Hubble Space Telescope, we obtained deep optical imaging of Andromeda II (And II; MV = ?12.0; log(M /M ?) ~ 6.7) and Andromeda XVI (And XVI; MV = ?7.5; log(M /M ?) ~ 4.9) yielding color-magnitude diagrams that extend at least 1?mag below the oldest main-sequence turnoff, and are similar in quality to those available for the MW companions. And II and And XVI show strikingly similar SFHs: both formed 50%-70% of their total stellar mass between 12.5 and 5?Gyr ago (z ~ 5-0.5) and both were abruptly quenched ~5?Gyr ago (z ~ 0.5). The predominance of intermediate age populations in And XVI makes it qualitatively different from faint companions of the MW and clearly not a pre-reionization fossil. Neither And II nor And XVI appears to have a clear analog among MW companions, and the degree of similarity in the SFHs of And II and And XVI is not seen among comparably faint-luminous pairs of MW satellites. These findings provide hints that satellite galaxy evolution may vary substantially among hosts of similar stellar mass. Although comparably deep observations of more M31 satellites are needed to further explore this hypothesis, our results underline the need for caution when interpreting satellite galaxies of an individual system in a broader cosmological context.

Edouard J Bernard - One of the best experts on this subject based on the ideXlab platform.

  • the islands project ii the lifetime star formation histories of six Andromeda dsphs
    The Astrophysical Journal, 2017
    Co-Authors: Evan D Skillman, Edouard J Bernard, M Monelli, Daniel R Weisz, Sebastian L Hidalgo, A Aparicio, Michael Boylankolchin, S Cassisi, A A Cole, Andrew E Dolphin
    Abstract:

    The Initial Star formation and Lifetimes of Andromeda Satellites (ISLAndS) project employs Hubble Space Telescope imaging to study a representative sample of six Andromeda dSph satellite companion galaxies. Our main goal is to determine whether the star formation histories (SFHs) of the Andromeda dSph satellites demonstrate significant statistical differences from those of the Milky Way (MW). Our deep observations yield a time resolution at the oldest ages of ∼1 Gyr, allowing meaningful comparisons to the MW satellites. The six dSphs present a variety of SFHs (e.g., a significant range in quenching times, τq, from 9 to 6 Gyr ago) that are not strictly correlated with luminosity or present distance from M31. In agreement with observations of MW companions of similar mass, there is no evidence of complete quenching of star formation by the cosmic UV background responsible for reionization, but the possibility of a degree of quenching at reionization cannot be ruled out. We do not find significant differences between the SFHs of the members and non-members of the vast, thin plane of satellites. The SFHs of the ISLAndS M31 dSphs appear to be more uniform than those of the MW dSphs. Specifically, the primary difference between the SFHs of the ISLAndS dSphs and MW dSph companions of similar luminosities and host distances is the absence of late-quenching (τq ⩽ 5 Gyr) dSphs in the ISLAndS sample. Thus, models that can produce satellite populations with and without late-quenching satellites are of extreme interest.

  • the islands project ii the lifetime star formation histories of six Andromeda dsphs
    arXiv: Astrophysics of Galaxies, 2016
    Co-Authors: Evan D Skillman, Edouard J Bernard, M Monelli, Daniel R Weisz, Sebastian L Hidalgo, A Aparicio, Michael Boylankolchin, S Cassisi, A A Cole, Andrew E Dolphin
    Abstract:

    The Initial Star formation and Lifetimes of Andromeda Satellites (ISLAndS) project uses Hubble Space Telescope imaging to study a representative sample of six Andromeda dSph satellite companion galaxies. The main goal of the program is to determine whether the star formation histories (SFHs) of the Andromeda dSph satellites demonstrate significant statistical differences from those of the Milky Way, which may be attributable to the different properties of their local environments. Our observations reach the oldest main sequence turn-offs, allowing a time resolution at the oldest ages of ~ 1 Gyr, which is comparable to the best achievable resolution in the MW satellites. We find that the six dSphs present a variety of SFHs that are not strictly correlated with luminosity or present distance from M31. Specifically, we find a significant range in quenching times (lookback times from 9 to 6 Gyr), but with all quenching times more than ~ 6 Gyr ago. In agreement with observations of Milky Way companions of similar mass, there is no evidence of complete quenching of star formation by the cosmic UV background responsible for reionization, but the possibility of a degree of quenching at reionization cannot be ruled out. We do not find significant differences between the SFHs of the three members of the vast, thin plane of satellites and the three off-plane dSphs. The primary difference between the SFHs of the ISLAndS dSphs and Milky Way dSph companions of similar luminosities and host distances is the absence of very late quenching (< 5 Gyr ago) dSphs in the ISLAndS sample. Thus, models that can reproduce satellite populations with and without late quenching satellites will be of extreme interest.

  • comparing m31 and milky way satellites the extended star formation histories of Andromeda ii and Andromeda xvi
    The Astrophysical Journal, 2014
    Co-Authors: Alan W Mcconnachie, Andrew E Dolphin, Evan D Skillman, M Monelli, Daniel R Weisz, Sebastian L Hidalgo, Edouard J Bernard
    Abstract:

    We present the first comparison between the lifetime star formation histories (SFHs) of M31 and Milky Way (MW) satellites. Using the Advanced Camera for Surveys on board the Hubble Space Telescope, we obtained deep optical imaging of Andromeda II (And II; MV = ?12.0; log(M /M ?) ~ 6.7) and Andromeda XVI (And XVI; MV = ?7.5; log(M /M ?) ~ 4.9) yielding color-magnitude diagrams that extend at least 1?mag below the oldest main-sequence turnoff, and are similar in quality to those available for the MW companions. And II and And XVI show strikingly similar SFHs: both formed 50%-70% of their total stellar mass between 12.5 and 5?Gyr ago (z ~ 5-0.5) and both were abruptly quenched ~5?Gyr ago (z ~ 0.5). The predominance of intermediate age populations in And XVI makes it qualitatively different from faint companions of the MW and clearly not a pre-reionization fossil. Neither And II nor And XVI appears to have a clear analog among MW companions, and the degree of similarity in the SFHs of And II and And XVI is not seen among comparably faint-luminous pairs of MW satellites. These findings provide hints that satellite galaxy evolution may vary substantially among hosts of similar stellar mass. Although comparably deep observations of more M31 satellites are needed to further explore this hypothesis, our results underline the need for caution when interpreting satellite galaxies of an individual system in a broader cosmological context.

  • comparing m31 and milky way satellites the extended star formation histories of Andromeda ii and Andromeda xvi
    arXiv: Astrophysics of Galaxies, 2014
    Co-Authors: Alan W Mcconnachie, Andrew E Dolphin, Evan D Skillman, M Monelli, Daniel R Weisz, Sebastian L Hidalgo, Edouard J Bernard
    Abstract:

    We present the first comparison between the lifetime star formation histories (SFHs) of M31 and Milky Way (MW) satellites. Using the Advanced Camera for Surveys aboard the Hubble Space Telescope, we obtained deep optical imaging of Andromeda II (M$_{V} = -$12.0; log(M$_{\star}$/M$_{\odot}$) $\sim$ 6.7) and Andromeda XVI (M$_{V} = -$7.5; log(M$_{\star}$/M$_{\odot}$) $\sim$ 4.9) yielding color-magnitude diagrams that extend at least 1 magnitude below the oldest main sequence turnoff, and are similar in quality to those available for the MW companions. And II and And XVI show strikingly similar SFHs: both formed 50-70% of their total stellar mass between 12.5 and 5 Gyr ago (z$\sim$5-0.5) and both were abruptly quenched $\sim$ 5 Gyr ago (z$\sim$0.5). The predominance of intermediate age populations in And XVI makes it qualitatively different from faint companions of the MW and clearly not a pre-reionization fossil. Neither And II nor And XVI appears to have a clear analog among MW companions, and the degree of similarity in the SFHs of And II and And XVI is not seen among comparably faint-luminous pairs of MW satellites. These findings provide hints that satellite galaxy evolution may vary substantially among hosts of similar stellar mass. Although comparably deep observations of more M31 satellites are needed to further explore this hypothesis, our results underline the need for caution when interpreting satellite galaxies of an individual system in a broader cosmological context.

  • perseus i a distant satellite dwarf galaxy of Andromeda
    The Astrophysical Journal, 2013
    Co-Authors: Eric F Bell, Hanswalter Rix, Nicolas F Martin, Annette M N Ferguson, Colin T Slater, Edward F Schlafly, Edouard J Bernard, Douglas P Finkbeiner, Benjamin P M Laevens
    Abstract:

    We present the discovery of a new dwarf galaxy, Perseus I/Andromeda XXXIII, found in the vicinity of Andromeda (M31) in stacked imaging data from the Pan-STARRS1 3π survey. Located 27.°9 away from M31, Perseus I has a heliocentric distance of 785 ± 65 kpc, compatible with it being a satellite of M31 at from its host. The properties of Perseus I are typical for a reasonably bright dwarf galaxy (MV = –10.3 ± 0.7), with an exponential half-light radius of rh = 1.7 ± 0.4 arcmin or at this distance, and a moderate ellipticity (). The late discovery of Perseus I is due to its fairly low surface brightness ( mag arcsec–2), and to the previous lack of deep, high quality photometric data in this region. If confirmed to be a companion of M31, the location of Perseus I, far east from its host, could place interesting constraints on the bulk motion of the satellite system of M31.

Annette M N Ferguson - One of the best experts on this subject based on the ideXlab platform.

  • the large scale structure of the halo of the Andromeda galaxy ii hierarchical structure in the pan Andromeda archaeological survey
    arXiv: Astrophysics of Galaxies, 2018
    Co-Authors: Alan W Mcconnachie, Mike Irwin, Nicolas F Martin, Annette M N Ferguson, Rodrigo A Ibata, Dougal A Mackey, Geraint F Lewis, Michelle L M Collins, Stephen D J Gwyn, T J Davidge
    Abstract:

    The Pan-Andromeda Archaeological Survey is a survey of $>400$ square degrees centered on the Andromeda (M31) and Triangulum (M33) galaxies that has provided the most extensive panorama of a $L_\star$ galaxy group to large projected galactocentric radii. Here, we collate and summarise the current status of our knowledge of the substructures in the stellar halo of M31, and discuss connections between these features. We estimate that the 13 most distinctive substructures were produced by at least 5 different accretion events, all in the last 3 or 4 Gyrs. We suggest that a few of the substructures furthest from M31 may be shells from a single accretion event. We calculate the luminosities of some prominent substructures for which previous estimates were not available, and we estimate the stellar mass budget of the outer halo of M31. We revisit the problem of quantifying the properties of a highly structured dataset; specifically, we use the OPTICS clustering algorithm to quantify the hierarchical structure of M31's stellar halo, and identify three new faint structures. M31's halo, in projection, appears to be dominated by two `mega-structures', that can be considered as the two most significant branches of a merger tree produced by breaking M31's stellar halo into smaller and smaller structures based on the stellar spatial clustering. We conclude that OPTICS is a powerful algorithm that could be used in any astronomical application involving the hierarchical clustering of points. The publication of this article coincides with the public release of all PAndAS data products.

  • comparing the observable properties of dwarf galaxies on and off the Andromeda plane
    The Astrophysical Journal, 2015
    Co-Authors: Alan W Mcconnachie, Nicolas F Martin, Annette M N Ferguson, Rodrigo A Ibata, S C Chapman, Michelle L M Collins, R M Rich, Michael J Irwin, Geraint F Lewis
    Abstract:

    The thin, extended planes of satellite galaxies detected around both the Milky Way and Andromeda are not a natural prediction of the Λ-cold dark matter paradigm. Galaxies in these distinct planes may have formed and evolved in a different way (e.g., tidally) from their off-plane neighbors. If this were the case, one would expect the on- and off-plane dwarf galaxies in Andromeda to have experienced different evolutionary histories, which should be reflected by the chemistries, dynamics, and star formation histories of the two populations. In this work, we present new, robust kinematic observations for two on-plane M31 dwarf spheroidal galaxies (And XVI and XVII) and compile and compare all available observational metrics for the on- and off-plane dwarfs to search for a signal that would corroborate such a hypothesis. We find that, barring their spatial alignment, the on- and off-plane Andromeda dwarf galaxies are indistinguishable from one another, arguing against vastly different formative and evolutionary histories for these two populations.

  • comparing the observable properties of dwarf galaxies on and off the Andromeda plane
    arXiv: Astrophysics of Galaxies, 2014
    Co-Authors: Alan W Mcconnachie, Nicolas F Martin, Annette M N Ferguson, Rodrigo A Ibata, S C Chapman, Michelle L M Collins, R M Rich, Michael J Irwin, Geraint F Lewis
    Abstract:

    The thin, extended planes of satellite galaxies detected around both the Milky Way and Andromeda are not a natural prediction of the LCDM paradigm. Galaxies in these distinct planes may have formed and evolved in a different way (e.g., tidally) to their off-plane neighbours. If this were the case, one would expect the on- and off-plane dwarf galaxies in Andromeda to have experienced different evolutionary histories, which should be reflected by the chemistries, dynamics, and star formation histories of the two populations. In this work, we present new, robust kinematic observations for 2 on-plane M31 dSphs (And XVI and XVII) and compile and compare all available observational metrics for the on- and off-plane dwarfs to search for a signal that would corroborate such a hypothesis. We find that, barring their spatial alignment, the on- and off-plane Andromeda dwarf galaxies are indistinguishable from one another, arguing against vastly different formative and evolutionary histories for these two populations.

  • perseus i a distant satellite dwarf galaxy of Andromeda
    The Astrophysical Journal, 2013
    Co-Authors: Eric F Bell, Hanswalter Rix, Nicolas F Martin, Annette M N Ferguson, Colin T Slater, Edward F Schlafly, Edouard J Bernard, Douglas P Finkbeiner, Benjamin P M Laevens
    Abstract:

    We present the discovery of a new dwarf galaxy, Perseus I/Andromeda XXXIII, found in the vicinity of Andromeda (M31) in stacked imaging data from the Pan-STARRS1 3π survey. Located 27.°9 away from M31, Perseus I has a heliocentric distance of 785 ± 65 kpc, compatible with it being a satellite of M31 at from its host. The properties of Perseus I are typical for a reasonably bright dwarf galaxy (MV = –10.3 ± 0.7), with an exponential half-light radius of rh = 1.7 ± 0.4 arcmin or at this distance, and a moderate ellipticity (). The late discovery of Perseus I is due to its fairly low surface brightness ( mag arcsec–2), and to the previous lack of deep, high quality photometric data in this region. If confirmed to be a companion of M31, the location of Perseus I, far east from its host, could place interesting constraints on the bulk motion of the satellite system of M31.

  • the large scale structure of the halo of the Andromeda galaxy part i global stellar density morphology and metallicity properties
    arXiv: Astrophysics of Galaxies, 2013
    Co-Authors: Rodrigo A Ibata, Nicolas F Martin, M J Irwin, Annette M N Ferguson, Arif Babul, Edouard J Bernard, Geraint F Lewis, Alan Mcconnachie, Scott Chapman, Michelle L M Collins
    Abstract:

    We present an analysis of the large-scale structure of the halo of the Andromeda galaxy, based on the Pan-Andromeda Archeological Survey (PAndAS), currently the most complete map of resolved stellar populations in any galactic halo. Despite copious substructure, the global halo populations follow closely power law profiles that become steeper with increasing metallicity. We divide the sample into stream-like populations and a smooth halo component. Fitting a three-dimensional halo model reveals that the most metal-poor populations ([Fe/H] -0.6). The space density of the smooth metal-poor component has a global power-law slope of -3.08+/-0.07, and a non-parametric fit shows that the slope remains nearly constant from 30kpc to 300kpc. The total stellar mass in the halo at distances beyond 2 degrees is 1.1x10^10 Solar masses, while that of the smooth component is 3x10^9 Solar masses. Extrapolating into the inner galaxy, the total stellar mass of the smooth halo is plausibly 8x10^9 Solar masses. We detect a substantial metallicity gradient, which declines from [Fe/H]=-0.7 at R=30kpc to [Fe/H]=-1.5 at R=150kpc for the full sample, with the smooth halo being 0.2dex more metal poor than the full sample at each radius. While qualitatively in-line with expectations from cosmological simulations, these observations are of great importance as they provide a prototype template that such simulations must now be able to reproduce in quantitative detail.

Hanswalter Rix - One of the best experts on this subject based on the ideXlab platform.

  • Andromeda s dust
    The Astrophysical Journal, 2013
    Co-Authors: B T Draine, G Aniano, O Krause, Brent Groves, Karin Sandstrom, R Braun, Adam K Leroy, U Klaas, Hendrik Linz, Hanswalter Rix
    Abstract:

    Spitzer Space Telescope and Herschel Space Observatory imaging of M31 is used, with a physical dust model, to construct maps of dust surface density, dust-to-gas ratio, starlight heating intensity, and polycyclic aromatic hydrocarbon (PAH) abundance, out to R ≈ 25 kpc. The global dust mass is M {sub d} = 5.4 × 10{sup 7} M {sub ☉}, the global dust/H mass ratio is M {sub d}/M {sub H} = 0.0081, and the global PAH abundance is (q {sub PAH}) = 0.039. The dust surface density has an inner ring at R = 5.6 kpc, a maximum at R = 11.2 kpc, and an outer ring at R ≈ 15.1 kpc. The dust/gas ratio varies from M {sub d}/M {sub H} ≈ 0.026 at the center to ∼0.0027 at R ≈ 25 kpc. From the dust/gas ratio, we estimate the interstellar medium metallicity to vary by a factor ∼10, from Z/Z {sub ☉} ≈ 3 at R = 0 to ∼0.3 at R = 25 kpc. The dust heating rate parameter (U) peaks at the center, with (U) ≈ 35, declining to (U) ≈ 0.25 at R = 20 kpc. Within the central kiloparsec, the starlight heating intensity inferred from themore » dust modeling is close to what is estimated from the stars in the bulge. The PAH abundance reaches a peak q {sub PAH} ≈ 0.045 at R ≈ 11.2 kpc. When allowance is made for the different spectrum of the bulge stars, q {sub PAH} for the dust in the central kiloparsec is similar to the overall value of q {sub PAH} in the disk. The silicate-graphite-PAH dust model used here is generally able to reproduce the observed dust spectral energy distribution across M31, but overpredicts 500 μm emission at R ≈ 2-6 kpc, suggesting that at R = 2-6 kpc, the dust opacity varies more steeply with frequency (with β ≈ 2.3 between 200 and 600 μm) than in the model.« less

  • perseus i a distant satellite dwarf galaxy of Andromeda
    The Astrophysical Journal, 2013
    Co-Authors: Eric F Bell, Hanswalter Rix, Nicolas F Martin, Annette M N Ferguson, Colin T Slater, Edward F Schlafly, Edouard J Bernard, Douglas P Finkbeiner, Benjamin P M Laevens
    Abstract:

    We present the discovery of a new dwarf galaxy, Perseus I/Andromeda XXXIII, found in the vicinity of Andromeda (M31) in stacked imaging data from the Pan-STARRS1 3π survey. Located 27.°9 away from M31, Perseus I has a heliocentric distance of 785 ± 65 kpc, compatible with it being a satellite of M31 at from its host. The properties of Perseus I are typical for a reasonably bright dwarf galaxy (MV = –10.3 ± 0.7), with an exponential half-light radius of rh = 1.7 ± 0.4 arcmin or at this distance, and a moderate ellipticity (). The late discovery of Perseus I is due to its fairly low surface brightness ( mag arcsec–2), and to the previous lack of deep, high quality photometric data in this region. If confirmed to be a companion of M31, the location of Perseus I, far east from its host, could place interesting constraints on the bulk motion of the satellite system of M31.

  • perseus i a distant satellite dwarf galaxy of Andromeda
    arXiv: Cosmology and Nongalactic Astrophysics, 2013
    Co-Authors: Eric F Bell, Hanswalter Rix, Nicolas F Martin, Annette M N Ferguson, Colin T Slater, Edward F Schlafly, Edouard J Bernard, Douglas P Finkbeiner, Benjamin P M Laevens
    Abstract:

    We present the discovery of a new dwarf galaxy, Perseus I/Andromeda XXXIII, found in the vicinity of Andromeda (M31) in stacked imaging data from the Pan-STARRS1 3{\pi} survey. Located 27.9{\deg} away from M31, Perseus I has a heliocentric distance of 785 +/- 65 kpc, compatible with it being a satellite of M31 at 374 +14/-10 kpc from its host. The properties of Perseus I are typical for a reasonably bright dwarf galaxy (M_V = -10.3 +/- 0.7), with an exponential half-light radius of r_h = 1.7 +/- 0.4 arcminutes or r_h = 400 +105/-85 pc at this distance, and a moderate ellipticity (\epsilon = 0.43 +0.15/-0.17). The late discovery of Perseus I is due to its fairly low surface brightness (\mu_0=25.7 +1.0/-0.9 mag/arcsec^2), and to the previous lack of deep, high quality photometric data in this region. If confirmed to be a companion of M31, the location of Perseus I, far east from its host, could place interesting constraints on the bulk motion of the satellite system of M31.

  • lacerta i and cassiopeia iii two luminous and distant Andromeda satellite dwarf galaxies found in the 3π pan starrs1 survey
    The Astrophysical Journal, 2013
    Co-Authors: Eric F Bell, Hanswalter Rix, Nicolas F Martin, Colin T Slater, Edward F Schlafly, E Morganson, Benjamin P M Laevens, Edouard J Bernard
    Abstract:

    We report the discovery of two new dwarf galaxies, Lacerta I/Andromeda XXXI (Lac I/And XXXI) and Cassiopeia III/Andromeda XXXII (Cas III/And XXXII), in stacked Pan-STARRS1 r P1- and i P1-band imaging data. Both are luminous systems (MV ~ –12) located at projected distances of 20.°3 and 10.°5 from M31. Lac I and Cas III are likely satellites of the Andromeda galaxy with heliocentric distances of and , respectively, and corresponding M31-centric distances of 275 ± 7 kpc and . The brightest of recent Local Group member discoveries, these two new dwarf galaxies owe their late discovery to their large sizes ( arcmin or for Lac I;  arcmin or 1456 ± 267 pc for Cas III) and consequently low surface brightness (μ0 ~ 26.0 mag arcsec–2), as well as to the lack of a systematic survey of regions at large radii from M31, close to the Galactic plane. This latter limitation is now alleviated by the 3π Pan-STARRS1 survey, which could lead to the discovery of other distant Andromeda satellite dwarf galaxies.

  • Andromeda s dust
    arXiv: Cosmology and Nongalactic Astrophysics, 2013
    Co-Authors: B T Draine, G Aniano, O Krause, Brent Groves, Karin Sandstrom, R Braun, Adam K Leroy, U Klaas, Hendrik Linz, Hanswalter Rix
    Abstract:

    Spitzer Space Telescope and Herschel Space Observatory imaging of M31 is used, with a physical dust model, to construct maps of dust surface density, dust-to-gas ratio, starlight heating intensity, and PAH abundance, out to R=25kpc. The global dust mass is M_d=5.4x10^7Msol, the global dust/H mass ratio is M_d/M_H=0.0081, and the global PAH abundance is =0.039. The dust surface density has an inner ring at R=5.6kpc, a maximum at R=11.2kpc, and an outer ring at R=15.1kpc. The dust/gas ratio varies from M_d/M_H=0.026 at the center to ~0.0027 at R=25kpc. From the dust/gas ratio, we estimate the ISM metallicity to vary by a factor ~10, from Z/Zsol=3 at R=0 to ~0.3 at R=25kpc. The dust heating rate parameter peaks at the center, with approx 35, declining to approx 0.25 at R=20kpc. Within the central kpc, the starlight heating intensity inferred from the dust modeling is close to what is estimated from the stars in the bulge. The PAH abundance reaches a peak q_PAH=0.045 at R=11.2kpc. When allowance is made for the different spectrum of the bulge stars, q_PAH for the dust in the central kpc is similar to the overall value of q_PAH in the disk. The silicate-graphite-PAH dust model used here is generally able to reproduce the observed dust spectral energy distribution across M31, but overpredicts 500um emission at R=2-6kpc, suggesting that at R=2-6kpc, the dust opacity varies more steeply with frequency (with beta approx 2.3 between 200 and 600um) than in the model