Project AMIGA: The Circumgalactic Medium of Andromeda*

Lehner, Nicolas; Berek, Samantha C.; Howk, J. C.; Wakker, Bart P.; Tumlinson, Jason; Jenkins, Edward B.; Prochaska, J. Xavier; Augustin, Ramona; Ji, Suoqing; Faucher-Giguère, Claude André; Hafen, Zachary; Peeples, Molly S.; Barger, Kat; Berg, Michelle A.; Bordoloi, Rongmon; Brown, Thomas M.; Fox, Andrew; Gilbert, Karoline M.; Guhathakurta, Puragra; Kalirai, Jason; Lockman, Felix J.; O’Meara, John M.; Pisano, D. J.; Ribaudo, Joseph; Werk, Jessica K.

doi:10.3847/1538-4357/aba49c

Cited by 80 publications

(101 citation statements)

References 186 publications

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“…C16 derived azimuthally averaged RGB metallicities spanning 70 projected kpc along the GSS by modeling PAndAS CMDs as a combination of weighted isochrones and an MW foreground contamination model (Martin et al 2013). C18 obtained CMD-based metallicities for individual RGB candidates in pencil-beam Hubble Space Telescope/Advanced Camera for Surveys fields from Project AMIGA (Lehner et al 2020) and Brown et al (2006) targeting the GSS at 21, 52, and 80 projected kpc. Neither C16 nor C18 correct for contamination of the GSS by M31ʼs kinematically hot stellar halo, although they show that 1) fields probing the GSS in M31-centric coordinates.…”

Section: Comparison To Previous Studiesmentioning

confidence: 99%

“…In addition, the most recent star formation in the GSS occured ∼4 Gyr ago, where the GSS has a typical stellar age of ∼8 Gyr (Brown et al 2006). Thus, a lower-mass progenitor would have produced lower 〈[α/Fe]〉 than is observed in the GSS: the progenitor's star formation would have quenched via interaction with M31ʼs ionized circumgalactic medium (Lehner et al 2020) only within the last few gigayears, providing sufficient time for Type Ia supernovae to deplete [α/Fe] with respect to [Fe/H]. The extended star formation history of the GSS similarly constrains the scenario of a high-mass progenitor (M å ∼ 10 10 M e ), although the interaction between M31 and the progenitor can begin as early as 5-10 Gyr ago in this case (D'Souza & Bell 2018;Hammer et al 2018).…”

Section: Implications For the Gss Progenitormentioning

confidence: 99%

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Elemental Abundances in M31: Gradients in the Giant Stellar Stream*

Escala

Gilbert

Wojno

et al. 2021

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We analyze existing measurements of [Fe/H] and [α/Fe] for individual red giant branch (RGB) stars in the Giant Stellar Stream (GSS) of M31 to determine whether spatial abundance gradients are present. These measurements were obtained from low-(R ∼ 3000) and moderate-(R ∼ 6000) resolution Keck/DEIMOS spectroscopy using spectral synthesis techniques as part of the Elemental Abundances in M31 survey. From a sample of 62 RGB stars spanning the GSS at 17, 22, and 33 projected kpc, we measure a [Fe/H] gradient of −0.018 ± 0.003 dex kpc −1 and negligible [α/Fe] gradient with M31-centric radius. We investigate GSS abundance patterns in the outer halo using additional [Fe/H] and [α/Fe] measurements for six RGB stars located along the stream at 45 and 58 projected kpc. These abundances provide tentative evidence that the trends in [Fe/H] and [α/Fe] beyond 40 kpc in the GSS are consistent with those within 33 kpc. We also compare the GSS abundances to 65 RGB stars located along the possibly related Southeast (SE) shelf substructure at 12 and 18 projected kpc. The abundances of the GSS and SE shelf are consistent, supporting a common origin hypothesis, although this interpretation may be complicated by the presence of [Fe/H] gradients in the GSS. We discuss the abundance patterns in the context of photometric studies from the literature and explore implications for the properties of the GSS progenitor, suggesting that the high 〈[α/Fe]〉 of the GSS (+0.40 ± 0.05 dex) favors a major merger scenario for its formation.

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Section: Comparison To Previous Studiesmentioning

confidence: 99%

Section: Implications For the Gss Progenitormentioning

confidence: 99%

Elemental Abundances in M31: Gradients in the Giant Stellar Stream*

Escala

Gilbert

Wojno

et al. 2021

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“…XMM, ROSAT, and Chandra were used to study its X-ray emission (Stiele et al 2010). Ultraviolet (UV) measurements were used to study interstellar extinction (Clayton et al 2015) as well as the circumgalactic medium, finding a very extended ionized medium which may overlap with a similar one originating from our Milky Way (Lehner et al 2020). Optical and near-infrared (NIR) observations were used to investigate the stellar composition (Sick et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Study of the thermal and nonthermal emission components in M31: the Sardinia Radio Telescope view at 6.6 GHz

Fatigoni

Radiconi

Battistelli

et al. 2021

A&A

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Context. The Andromeda galaxy is the best-known large galaxy besides our own Milky Way. Several images and studies exist at all wavelengths from radio to hard X-ray. Nevertheless, only a few observations are available in the microwave range where its average radio emission reaches the minimum. Aims. In this paper, we want to study the radio morphology of the galaxy, decouple thermal from nonthermal emission, and extract the star formation rate. We also aim to derive a complete catalog of radio sources for the mapped patch of sky. Methods. We observed the Andromeda galaxy with the Sardinia Radio Telescope at 6.6 GHz with very high sensitivity and angular resolution, and an unprecedented sky coverage. Results. Using new 6.6 GHz data and Effelsberg radio telescope ancillary data, we confirm that, globally, the spectral index is ∼0.7−0.8, while in the star forming regions it decreases to ∼0.5. By disentangling (gas) thermal and nonthermal emission, we find that at 6.6 GHz, thermal emission follows the distribution of HII regions around the ring. Nonthermal emission within the ring appears smoother and more uniform than thermal emission because of diffusion of the cosmic ray electrons away from their birthplaces. This causes the magnetic fields to appear almost constant in intensity. Furthermore, we calculated a map of the star formation rate based on the map of thermal emission. Integrating within a radius of Rmax = 15 kpc, we obtained a total star formation rate of 0.19 ± 0.01 M⊙ yr−1 in agreement with previous results in the literature. Finally, we correlated our radio data with infrared images of the Andromeda galaxy. We find an unexpectedly high correlation between nonthermal and mid-infrared data in the central region, with a correlation parameter r = 0.93. Finally, by computing the logarithmic 24μm/21cm ratio q24 μm, we find a decreasing trend with increasing galactocentric distance and an increasing dispersion. The logarithmic far-infrared-to-radio ratio is found to be 2.41 ± 0.04.

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“…Recent studies have begun to concentrate on absorption-line systems associated with more than one galaxy (Burchett et al 2016;Bielby et al 2017;Péroux et al 2017Péroux et al , 2019Pointon et al 2017;Pointon et al 2020;Nielsen et al 2018;Rahmani et al 2018a;Chen et al 2019;Hamanowicz et al 2020;Lehner et al 2020). It has been found that there is no strong anti-correlation between the equivalent width of Mg absorption and impact parameter for galaxy groups (Chen et al 2010b;Nielsen et al 2018), which differs from the strong anti-correlation found for isolated galaxies (e.g.…”

Section: Introductionmentioning

confidence: 93%

Disentangling the multiphase circumgalactic medium shared between a dwarf and a massive star-forming galaxy at z∼0.4

Nateghi

Kacprzak

Nielsen

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The multi-phase circumgalactic medium (CGM) arises within the complex environment around a galaxy, or collection of galaxies, and possibly originates from a wide range of physical mechanisms. In this paper, we attempt to disentangle the origins of these multi-phase structures and present a detailed analysis of the quasar field Q0122−003 field using Keck/KCWI galaxy observations and HST/COS spectra probing the CGM. Our re-analysis of this field shows that there are two galaxies associated with the absorption. We have discovered a dwarf galaxy, G_27kpc (M⋆ = 108.7 M⊙), at z = 0.39863 that is 27 kpc from the quasar sightline. G_27kpc is only +21 km s−1 from a more massive (M⋆ = 1010.5 M⊙) star-forming galaxy, G_163kpc, at an impact parameter of 163 kpc. While G_163kpc is actively forming stars (SFR = 6.9 M⊙ yr−1), G_27kpc has a low star-formation rate (SFR = 0.08 ± 0.03 M⊙ yr−1) and star formation surface density (ΣSFR = 0.006 M⊙ kpc−2 yr−1), implying no active outflows. By comparing galaxy SFRs, kinematics, masses and distances from the quasar sightline to the absorption kinematics, column densities and metallicities, we have inferred the following: (1) Part of the low-ionization phase has a metallicity and kinematics consistent with being accreted onto G_27kpc. (2) The remainder of the low ionization phase has metallicities and kinematics consistent with being intragroup gas being transferred from G_27kpc to G_163kpc. (3) The high ionization phase is consistent with being produced solely by outflows originating from the massive halo of G_163kpc. Our results demonstrate the complex nature of the multi-phase CGM, especially around galaxy groups, and that detailed case-by-case studies are critical for disentangling its origins.

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Project AMIGA: The Circumgalactic Medium of Andromeda*

Cited by 80 publications

References 186 publications

Elemental Abundances in M31: Gradients in the Giant Stellar Stream*

Elemental Abundances in M31: Gradients in the Giant Stellar Stream*

Study of the thermal and nonthermal emission components in M31: the Sardinia Radio Telescope view at 6.6 GHz

Disentangling the multiphase circumgalactic medium shared between a dwarf and a massive star-forming galaxy at z∼0.4

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